1996 Aerostar Brake System Diagnostics
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1996 Ford Truck Aerostar AWD V6-245 4.0L
Copyright © 2008, ALLDATA
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Brakes and Traction Control: Testing and Inspection Inspection and Verification (Start Testing Here) 1. Visually examine front and rear tires and wheel assemblies for damage such as uneven wear, tread washouts, or sidewall damage. Make sure the tires are of the same size, type and, where possible, same manufacturer. Any tire or wheel that is damaged should be replaced. 2. Wheels and tires must be cleared of any foreign matter, and tire pressures adjusted to the correct psi. 3. If tires exhibit uneven wear or feathering, the cause must be corrected. Check steering and suspension components for damage/wear and, if necessary, check and adjust steering alignment.
Brake Roughness, Vibration or Pulsation POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required. POSSIBLE SOURCE(S): ^ Excessive rotor runout, or thickness variation. ACTION(S) TO TAKE: ^ Service or replace rotor as required.
Brake Warning Light On POSSIBLE SOURCE(S): ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, check for leaks, and bleed system if required. POSSIBLE SOURCE(S): ^ Parking brake applied or not returning completely. ACTION(S) TO TAKE: ^ Release parking brake. POSSIBLE SOURCE(S): ^ Shorted light circuit. ACTION(S) TO TAKE: ^ Correct short in warning circuit. POSSIBLE SOURCE(S): ^ Damaged fluid level switch or float assembly. ACTION(S) TO TAKE: ^ Replace plastic reservoir assembly. POSSIBLE SOURCE(S): ^ Differential pressure switch shuttled due to leakage in hydraulic circuit or damaged differential switch. ACTION(S) TO TAKE: ^ Repair leakage in hydraulic circuit or replace combination valve. POSSIBLE SOURCE(S): ^ Anti-Lock light does self check. ACTION(S) TO TAKE: ^ Refer to Anti-lock Brakes. See: Antilock Brakes / Traction Control Systems/Testing and Inspection/Testing and Inspection Procedures/Displaying & Reading Trouble Codes
1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Damaged combination valve. ACTION(S) TO TAKE: ^ Replace as required.
Brakes Drag, Slow or Incomplete Release POSSIBLE SOURCE(S): ^ Parking brake control or parking brake rear cable and conduits (2A635) binding. ACTION(S) TO TAKE: ^ Repair, lubricate, or replace parts as required. POSSIBLE SOURCE(S): ^ Brake drum binding. ACTION(S) TO TAKE: ^ Repair, lubricate, or replace parts as required. POSSIBLE SOURCE(S): ^ Damaged front wheel bearing. ACTION(S) TO TAKE: ^ Check bearings for adjustment, wear, damage. Adjust bearings. POSSIBLE SOURCE(S): ^ Worn or damaged brake master cylinder. ACTION(S) TO TAKE: ^ Perform a master cylinder diagnosis test. Repair as required. POSSIBLE SOURCE(S): ^ Caliper slides binding. ACTION(S) TO TAKE: ^ Replace slide pins, clean grooves, lubricate slides. POSSIBLE SOURCE(S): ^ Brakes out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes POSSIBLE SOURCE(S): ^ Restriction in hydraulic system. ACTION(S) TO TAKE: ^ Inspect the hydraulic system, then repair or replace as required. POSSIBLE SOURCE(S): ^ Binding/seized rear wheel cylinders or caliper pistons. ACTION(S) TO TAKE: ^ Repair or replace as required.
Brakes Grab or Lock When Applied POSSIBLE SOURCE(S): ^ Tires worn or incorrect pressure. ACTION(S) TO TAKE: ^ Inflate tires to correct pressure. If tires have worn tread, replace them.
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1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Grease or fluid on linings, or damaged linings. ACTION(S) TO TAKE: ^ Inspect, repair, or replace lining in sets. Clean rotors. POSSIBLE SOURCE(S): ^ Improper size or type of linings. ACTION(S) TO TAKE: ^ Replace with correct brake linings in sets. POSSIBLE SOURCE(S): ^ Over-reaction of brake booster. ACTION(S) TO TAKE: ^ Check brake booster for over-reaction by comparing with a known quality vehicle. Replace brake booster if required. POSSIBLE SOURCE(S): ^ Lining sensitivity to moisture. ^ Other brake system components: - Loose or missing pins for caliper attachment. - Worn, damaged or dry wheel bearings. ACTION(S) TO TAKE: ^ Inspect, repair, replace or lubricate components if required POSSIBLE SOURCE(S): ^ RABS Valve: defective outlet (dump) valve. ACTION(S) TO TAKE: ^ Refer to Symptom Diagnosis, Symptom B -- first item only.
Brakes Pull to One Side POSSIBLE SOURCE(S): ^ Unequal air pressure in tires. ACTION(S) TO TAKE: ^ Inflate tires to correct pressure. POSSIBLE SOURCE(S): ^ Grease or fluid on linings. Glazed linings. ACTION(S) TO TAKE: ^ Clean, sand or replace linings. Clean drums or rotors. POSSIBLE SOURCE(S): ^ Loose or missing disc brake caliper pin. ACTION(S) TO TAKE: ^ Replace missing pin. POSSIBLE SOURCE(S): ^ Improper size or type of lining on one wheel. ACTION(S) TO TAKE: ^ Replace with correct brake linings in sets. POSSIBLE SOURCE(S): ^ Improper size wheel cylinder on one wheel. ACTION(S) TO TAKE: ^ Replace with correct wheel cylinder.
1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Stuck or seized pistons in wheel cylinders or seized calipers. ACTION(S) TO TAKE: ^ Repair or replace wheel cylinders or calipers as required. POSSIBLE SOURCE(S): ^ Restricted brake lines or hoses. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE(S): ^ Other brake components. - Improper adjustment of drum brakes. - Improper positioning of disc brake shoe and lining in the caliper. - Fit of caliper shoes to knuckle. - Improperly adjusted, damaged or worn wheel bearings. - Distorted drum brake shoes. - Worn brake linings or scored rotor. - Missing, broken or stretched retracting or retaining springs and clips. ACTION(S) TO TAKE: ^ Inspect, adjust, repair or replace as required POSSIBLE SOURCE(S): ^ Suspension or steering. ACTION(S) TO TAKE: ^ Repair Suspension or steering as required.
Brakes Vibrate During Application POSSIBLE SOURCE(S): ^ Improperly lubricated wheel bearings. ACTION(S) TO TAKE: ^ Service as required. POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace as required. POSSIBLE SOURCE(S): ^ Binding caliper sliders. ACTION(S) TO TAKE: ^ Service as required.
Empty Reservoir POSSIBLE SOURCE(S): ^ Leaking brake master cylinder. ACTION(S) TO TAKE: ^ Reposition gasket and brake master cylinder. POSSIBLE SOURCE(S): ^ Leaking mounting grommets. ACTION(S) TO TAKE: ^ Replace grommets and brake master cylinder reservoir.
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1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Leaking components (lines, hoses, front disc brake calipers, rear wheel cylinder, etc.). ACTION(S) TO TAKE: ^ Repair as required. Bleed system as required.
Excessive Brake Lining Wear POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required. POSSIBLE SOURCE(S): ^ Binding caliper sliders. ACTION(S) TO TAKE: ^ Service caliper sliders as required.
Excessive Brake Pedal Effort to Fully Apply Brakes POSSIBLE SOURCE(S): ^ Overloaded vehicle. ACTION(S) TO TAKE: ^ Lighten load and advise owner of correct load limits of vehicle. POSSIBLE SOURCE(S): ^ Insufficient vacuum to power brake booster. ACTION(S) TO TAKE: ^ Replace damaged or leaking vacuum booster hoses (2A047). POSSIBLE SOURCE(S): ^ Restricted air filter on brake pedal. ACTION(S) TO TAKE: ^ Clean or replace filter. POSSIBLE SOURCE(S): ^ Booster and brake pedal linkage binding caused by worn bushings or corrosion. ACTION(S) TO TAKE: ^ Replace worn bushings or clean and lubricate linkage. POSSIBLE SOURCE(S): ^ Worn or damaged power brake booster. ACTION(S) TO TAKE: ^ Replace power brake booster. POSSIBLE SOURCE(S): ^ Brake lining worn, glazed, contaminated or improper type. ACTION(S) TO TAKE: ^ Replace brake lining in axle sets. POSSIBLE SOURCE(S): ^ Rear brake shoe and lining improperly installed. ACTION(S) TO TAKE: ^ Reposition brake shoes properly and eliminate any binding.
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1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Seized wheel cylinder pistons in rear wheel cylinders or front disc brake calipers. ^ Restricted brake lines or hoses. ACTION(S) TO TAKE: ^ Repair or replace as required.
With Rear Anti-Lock Brakes POSSIBLE SOURCE: ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, bleed system, check for leaks. POSSIBLE SOURCE: ^ Worn or damaged RABS valve accumulator or outlet (dump) valve. ACTION(S) TO TAKE: ^ Refer to Diagnosis By Symptom Test C. See: Antilock Brakes / Traction Control Systems/Testing and Inspection/Testing and Inspection Procedures/Diagnosis By Symptom/Symptom Diagnosis Procedures/Symptom C: Hard or Soft Brake Pedal
POSSIBLE SOURCE: ^ Brake drums out of adjustment.
ACTION(S) TO TAKE: ^ Adjust rear brakes.
POSSIBLE SOURCE: ^ Front wheel bearing out of adjustment.
ACTION(S) TO TAKE: ^ Adjust front wheel bearings.
POSSIBLE SOURCE: ^ Brake master cylinder or booster dash unit mounting loose.
ACTION(S) TO TAKE: ^ Tighten nuts and bolts as required.
POSSIBLE SOURCE: ^ Disc brake caliper attachment loose.
ACTION(S) TO TAKE: ^ Replace or tighten as required.
POSSIBLE SOURCE: ^ Worn or damaged brake shoe adjusting lever cables (2A178).
ACTION(S) TO TAKE: ^ Remove drum and check lining for proper adjustment. Replace brake shoe adjusting lever cables.
POSSIBLE SOURCE: ^ Glazed, worn, scored or damaged brake linings.
ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings.
POSSIBLE SOURCE: ^ Drums out-of-round or rotors with excessive runout.
ACTION(S) TO TAKE: ^ Refinish, or replace if wear exceeds limits.
POSSIBLE SOURCE: ^ Front brake hose (2078) improperly positioned.
1996 Ford Truck Aerostar AWD V6-245 4.0L
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ACTION(S) TO TAKE: ^ Check front brake hose for mis-position near heat source. Reposition as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. POSSIBLE SOURCE: ^ Reservoir cap vent hole clogged. ACTION(S) TO TAKE: ^ Service or replace brake master cylinder filler cap (2162) as required.
With 4 Wheel Anti-Lock Brakes POSSIBLE SOURCE: ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, bleed system, check for leaks (Brake Bleeding). POSSIBLE SOURCE: ^ Worn or damaged four wheel ABS hydraulic control unit. ACTION(S) TO TAKE: ^ Refer to Symptom C (Soft/Hard Pedal). POSSIBLE SOURCE: ^ Brake drums out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes. POSSIBLE SOURCE: ^ Front wheel bearing out of adjustment. ACTION(S) TO TAKE: ^ Adjust front wheel bearings. POSSIBLE SOURCE: ^ Brake master cylinder or booster dash unit mounting loose. ACTION(S) TO TAKE: ^ Tighten nuts and bolts as required. POSSIBLE SOURCE: ^ Disc brake caliper attachment loose. ACTION(S) TO TAKE: ^ Replace or tighten as required. POSSIBLE SOURCE: ^ Worn or damaged brake shoe adjusting lever cables. ACTION(S) TO TAKE: ^ Remove drum and check lining for proper adjustment. Replace brake shoe adjusting lever cables. POSSIBLE SOURCE: ^ Glazed, worn, scored or damaged brake linings. ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings.
1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE: ^ Drums out-of-round or rotors with excessive runout. ACTION(S) TO TAKE: ^ Refinish, or replace if wear exceeds limits. POSSIBLE SOURCE: ^ Front brake hose (2078) improperly positioned. ACTION(S) TO TAKE: ^ Check front brake hose for mis-position near heat source. Reposition as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. See: Brake Bleeding POSSIBLE SOURCE: ^ Reservoir cap vent hole clogged. ACTION(S) TO TAKE: ^ Service or replace brake master cylinder filler cap (2162) as required.
Excessive Pedal Travel/Brake Pedal Goes to Floor Consistently POSSIBLE SOURCE: ^ Hydraulic system. ACTION(S) TO TAKE: ^ Perform master cylinder diagnosis test. POSSIBLE SOURCE: ^ Brake drums out of adjustment, worn, bad wear pattern, or cracked drums. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE: ^ Loose or improper attachment of brake pedal, pedal support booster and brake master cylinder. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE: ^ External leak. ACTION(S) TO TAKE: ^ Repair as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. See: Brake Bleeding POSSIBLE SOURCE: ^ Insufficient brake pedal reserve. ACTION(S) TO TAKE: ^ Go to Test D.
Grinding Noise
1996 Ford Truck Aerostar AWD V6-245 4.0L
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POSSIBLE SOURCE(S): ^ Improperly lubricated wheel bearings. ACTION(S) TO TAKE: ^ Service wheel bearings as required.
Groan, Roughness or Chatter at Wheel (Brakes Applied) POSSIBLE SOURCE(S): ^ Loose wheel lugnuts. ACTION(S) TO TAKE: ^ Tighten to 85-105 ft lb. Replace wheel if stud holes are elongated POSSIBLE SOURCE(S): ^ Worn, damaged, dry or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Inspect, lubricate or replace. POSSIBLE SOURCE(S): ^ Loose or worn front suspension components. ACTION(S) TO TAKE: ^ Inspect, repair or replace front suspension components as required. POSSIBLE SOURCE(S): ^ Brake drum cracked or out-of-round. ACTION(S) TO TAKE: ^ Replace drum if required. POSSIBLE SOURCE(S): ^ Disc brake caliper backing plate and anchor plate loose, or missing parts, also loose or bent dust shield. ACTION(S) TO TAKE: ^ Repair or replace parts as required. POSSIBLE SOURCE(S): ^ Excessive wear or lateral run-out of rotor. ACTION(S) TO TAKE: ^ Replace rotor. POSSIBLE SOURCE(S): ^ Worn tires. ACTION(S) TO TAKE: ^ Replace tires.
Low Pedal POSSIBLE SOURCE(S): ^ Hydraulic system. ACTION(S) TO TAKE: ^ Perform diagnosis. Repair as required. POSSIBLE SOURCE(S): ^ Front wheel bearings out of adjustment. ACTION(S) TO TAKE:
1996 Ford Truck Aerostar AWD V6-245 4.0L ^
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Adjust front wheel bearings.
POSSIBLE SOURCE(S): ^ Brake drums out of adjustment, worn, bad wear pattern or cracked brake drums. ACTION(S) TO TAKE: ^ Adjust or replace as required. POSSIBLE SOURCE(S): ^ Loose or improper attachment of brake pedal, pedal support, power brake booster and brake master cylinder. ACTION(S) TO TAKE: ^ Repair or replace components as required.
Noise at Wheels -- Brakes Applied -- Squeak or Squeal POSSIBLE SOURCE(S): ^ Worn or scored brake drums and lining or front disc brake hub and rotors (1102). ACTION(S) TO TAKE: ^ Inspect, repair or replace as required. POSSIBLE SOURCE(S): ^ Burrs or rust on front disc brake caliper that would obstruct seating of shoe to front disc brake caliper. ACTION(S) TO TAKE: ^ Clean or deburr front disc brake caliper. POSSIBLE SOURCE(S): ^ Dirty, greased or glazed linings. ACTION(S) TO TAKE: ^ Clean or replace. POSSIBLE SOURCE(S): ^ Improper lining parts or loose rear brake adjustment. ACTION(S) TO TAKE: ^ Inspect for correct usage. If necessary replace with correct type in axle sets. POSSIBLE SOURCE(S): ^ Other brake system components. - Loose lining rivets. - Weak, damaged or incorrect brake shoe retracting springs (2296). - Loose or damaged shoe retaining pins, brake shoe retracting springs and clips. - Grooved backing plate ledges. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required.
Noise at Wheels -- Brakes Not Applied -- Squeak or Squeal POSSIBLE SOURCE(S): ^ Wheel covers improperly attached. ACTION(S) TO TAKE: ^ Seat covers with a rubber mallet. Repair flanges or replace cover. POSSIBLE SOURCE(S): ^ Loose wheel attaching lugnuts. ACTION(S) TO TAKE: ^ Tighten to proper 85-105 ft lb. Replace wheel if stud holes are damaged. POSSIBLE SOURCE(S):
1996 Ford Truck Aerostar AWD V6-245 4.0L ^
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Worn, dry or improperly adjusted wheel bearings.
ACTION(S) TO TAKE: ^ Replace worn or damaged wheel bearings. Lubricate and adjust. POSSIBLE SOURCE(S): ^ Glazed linings -- adjustment too tight. ACTION(S) TO TAKE: ^ Remove glaze from linings. Adjust brakes properly. POSSIBLE SOURCE(S): ^ Other brake system components. - Stretched brake shoe retracting springs. - Bent or warped brake backing plate causing interference with brake drum. - Improper positioning of disc brake pad in front disc brake caliper. - Excessive runout of front disc brake rotor. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required.
Noise at Wheels When Brakes Applied/Scrape or Grind POSSIBLE SOURCE(S): ^ Worn brake linings, loose rivets or foreign material between lining and brake drum or front disc brake rotor. ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings. Refinish or replace brake drums or front disc brake rotors if excessively scored POSSIBLE SOURCE(S): ^ Brake shoe interference with back of brake drum, shield-to-rotor clearance or binding at backing plate guide ledges. ACTION(S) TO TAKE: ^ Inspect. Replace as necessary. Lubricate. POSSIBLE SOURCE(S): ^ Other brake system components. - Warped or bent brake backing plate causing interference with brake drum. - Cracked brake drums or rotors. - Loose brake shoe hold down springs. ACTION(S) TO TAKE: ^ Inspect and repair as necessary POSSIBLE SOURCE(S): ^ Tires rubbing against chassis, body, or loose brake shoe hold down springs. ACTION(S) TO TAKE: ^ Inspect. Repair as necessary.
Noise at Wheels When Brakes Applied/Snap or Click POSSIBLE SOURCE(S): ^ Cracked welds at brake shoe web. ACTION(S) TO TAKE: ^ Replace rear brake shoe and lining in axle sets. POSSIBLE SOURCE(S): ^ Brake shoes binding at backing plate ledges. ACTION(S) TO TAKE: ^ Clean and lubricate ledges. POSSIBLE SOURCE(S):
1996 Ford Truck Aerostar AWD V6-245 4.0L ^
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Machining marks on brake drums.
ACTION(S) TO TAKE: ^ Refinish, or replace brake drums. POSSIBLE SOURCE(S): ^ Backing plate ledges worn. ACTION(S) TO TAKE: ^ Replace brake backing plate and lubricate ledges POSSIBLE SOURCE(S): ^ Loose or missing disc brake pad anti-rattle clips (2B164). ACTION(S) TO TAKE: ^ Replace clips. POSSIBLE SOURCE(S): ^ Improper rotor finish after turning. ACTION(S) TO TAKE: ^ Refinish or replace front disc brake rotors (1125) POSSIBLE SOURCE(S): ^ Improper positioning, wear or damage of front disc brake caliper. ACTION(S) TO TAKE: ^ Inspect, repair or replace disc brake caliper(s).
Noise at Wheels, Brakes Not Applied/Growling, Click or Rattle POSSIBLE SOURCE(S): ^ Stones or foreign material trapped inside wheel covers. ACTION(S) TO TAKE: ^ Remove stones, etc. POSSIBLE SOURCE(S): ^ Loose wheel lugnuts. ACTION(S) TO TAKE: ^ Tighten to 85-105 ft lb. Replace wheel if stud holes are elongated. POSSIBLE SOURCE(S): ^ Damaged, worn, or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace as required.
Noise at Wheels, Brakes Not Applied/Squeaks, Squeals or Chatter POSSIBLE SOURCE(S): ^ Brake backing plate. - Loose or missing anti-rattle clips, or caliper pins. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required. POSSIBLE SOURCE(S): ^ Drum brake linings/shoes loose or extra parts. ACTION(S) TO TAKE: ^ Inspect, remove or repair. POSSIBLE SOURCE(S):
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1996 Ford Truck Aerostar AWD V6-245 4.0L ^
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Worn, damaged or dry wheel bearings.
ACTION(S) TO TAKE: ^ Inspect, lubricate or replace. Adjust wheel bearings.
Parking Brake Will Not Hold POSSIBLE SOURCE(S): ^ Parking brake rear cable and conduit out of adjustment. ACTION(S) TO TAKE: ^ Adjust parking brake rear cable and conduits POSSIBLE SOURCE(S): ^ Brake drums out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes. POSSIBLE SOURCE(S): ^ Primary brake shoe parking brake lever link (2A642) or parking brake rear cable and conduits, release lever, clevis and ratchet binding, worn or damaged. ACTION(S) TO TAKE: ^ Repair or replace parking brake linkage or cables as required.
Parking Brake Will Not Release or Fully Return POSSIBLE SOURCE(S): ^ Manual release brake control components binding or damaged. ACTION(S) TO TAKE: ^ Repair or replace rear parking brake cable. POSSIBLE SOURCE(S): ^ Primary brake shoe parking brake lever link and parking brake rear cable and conduits binding. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE(S): ^ Worn or damaged rear brake components. ACTION(S) TO TAKE: ^ Check rear brake shoe retracting springs and rear parking brake cables. Repair as required. POSSIBLE SOURCE(S): ^ Parking brake improperly adjusted. ACTION(S) TO TAKE: ^ Adjust as required.
Vibration When Brakes Are Applied POSSIBLE SOURCE(S): ^ Loose lugnuts. ACTION(S) TO TAKE: ^ Tighten lugnuts to 85-105 ft lb. Replace rim if stud holes are elongated.
POSSIBLE SOURCE(S): ^ Cracked front disc brake rotors.
ACTION(S) TO TAKE:
1996 Ford Truck Aerostar AWD V6-245 4.0L ^
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Replace front disc brake rotor.
POSSIBLE SOURCE(S): ^ Front disc brake rotors/brake drums out-of-round or improper machining. ACTION(S) TO TAKE: ^ Machine rotors or replace as required. POSSIBLE SOURCE(S): ^ Worn or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required POSSIBLE SOURCE(S): ^ Loose or worn front suspension components. ACTION(S) TO TAKE: ^ Tighten loose components. Replace worn or damaged components. POSSIBLE SOURCE(S): ^ Excessive radial or lateral run-out on wheel and tire. ACTION(S) TO TAKE: ^ Adjust or replace tire or wheel to eliminate excessive run-out on tire or wheel as required.
A1 - Inspect Tire Pressure ^ Measure air pressure in all four tires. ^ Is tire pressure within specifications? YES -- Go to A2. See: Pinpoint Tests/A - Brakes Pull or Drift/A2 - Check Caliper and Rear Wheel Cylinders NO -- Adjust tire pressure.
A2 - Check Caliper and Rear Wheel Cylinders ^ Check the front disc brake caliper pistons, pins or rear wheel cylinders (2261) for binding, leakage or sticking. ^ Do the front disc brake caliper pistons, pins or rear wheel cylinders bind or stick? YES -- Repair or replace components as necessary. NO -- Go to A3. See: Pinpoint Tests/A - Brakes Pull or Drift/A3 - Inspect Front Disc Brake Rotors and Brake Drums
A3 - Inspect Front Disc Brake Rotors and Brake Drums ^ Inspect the disc brake rotors and/or brake drums (1126) for excessive runout or damage. ^ Does excessive runout or damage exist? YES -- Repair or replace disc brake rotor or brake drum as necessary. NO -- Go to A4. See: Pinpoint Tests/A - Brakes Pull or Drift/A4 - Inspect Wheel Bearings
A4 - Inspect Wheel Bearings ^ Inspect front and rear wheel bearings for excessive end play or improper preload. ^ Does excessive end play or improper wheel bearing preload exist? YES -- Adjust wheel bearing preload or Replace wheel bearings. NO -- Inspect for and Repair hydraulic leaks. Retest system.
1996 Ford Truck Aerostar AWD V6-245 4.0L
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B1 - Check Parking Brake Switch ^ With parking brake fully released, disconnect the parking brake switch at the parking brake control. ^ Did brake warning indicator light go out? YES -- Replace the parking brake switch. Retest. NO -- Go to B2. See: Pinpoint Tests/B - Brake Warning Indicator Always ON/B2 - Isolate Circuits, 531 (DG/R), 977 (P/W), and 162 (Lg/R)
B2 - Isolate Circuits, 531 (DG/R), 977 (P/W), and 162 (Lg/R) ^ With brake master cylinder reservoir fluid level OK, disconnect the brake master cylinder fluid level switch connector at the brake master cylinder reservoir (2K478). ^ Does the brake warning indicator light go out? YES -- Go to B3. See: Pinpoint Tests/B - Brake Warning Indicator Always ON/B3 - Test Brake Fluid Level Indicator Switch NO -- Service ground short in circuit 531 (DG/Y), 977 (P/W), or 162 (LG/R).
B3 - Test Brake Fluid Level Indicator Switch ^ With the brake master cylinder reservoir fluid level OK, disconnect the fluid level switch connector. At the reservoir side of the connector, test for a ground at Circuits 531 (DG/Y) and 512 (T/LG).
Fluid Level Switch Connector ^ In which circuit is ground detected? 531 - Replace the brake master cylinder reservoir. 512 - Service the ground short in circuit 512 (T/LG).
C1 - Isolate Vibration/Shudder ^ Determine if vibration/shudder is induced by the rear brakes by using the parking brake to slow the vehicle from approximately 80 to 56 km/h (50 to 35 mph). To use the parking brake: ^ Hold the release handle out, or press release button in, while applying the parking brake. ^ Is vibration/shudder present? YES -- Check the rear brakes. Go to C2 for disc brakes. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C2 - Resurface Disc Brakes Go to C3 for drum brakes. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C3 - Refinish Brake Drums NO -- Check the front brakes. Go to C2. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C2 - Resurface Disc Brakes
C2 - Resurface Disc Brakes ^ Resurface front disc brake rotors (1125) and road test vehicle. ^ Is shudder/vibration present? YES -- Go to C4. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C4 - Replace Disc Brake Pads
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NO -- Brake system repaired.
C3 - Refinish Brake Drums ^ Refinish brake drums and road test vehicle. ^ Is shudder/vibration present? YES -- Go to C5. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C5 - Replace Brake Shoes and Linings NO -- Brake system repaired.
C4 - Replace Disc Brake Pads ^ Replace disc brake pads and road test vehicle. ^ Is shudder/vibration present? YES -- Replace front disc brake rotors. NO -- Brake system repaired.
C5 - Replace Brake Shoes and Linings ^ Replace rear brake shoes and linings (2200) and road test vehicle. ^ Is shudder/vibration present? YES -- Determine which brake drum or rotor is at fault and replace. NO -- Brake system repaired.
D1 - Road Test ^ Road test vehicle only if condition cannot be verified in shop. ^ Statically depress brake pedal (2455). ^ Does brake pedal operate properly? YES -- Vehicle OK. NO -- Go to D2. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D2 - Check Brake Fluid Level
D2 - Check Brake Fluid Level ^ Check brake fluid level. ^ Is fluid level within specifications? YES -- Go to D3. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D3 - Pressurize System NO -- Check reservoir sealing points. Add fluid and Bleed system. Repeat test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 - Road Test
D3 - Pressurize System ^ Pump brake pedal rapidly (five times). ^ Does brake pedal maintain height throughout test? YES -- Check rear brake adjustment and adjust if necessary. If condition still exists, bleed system. Repeat test D1. See: Pinpoint Tests/D Brake Pedal Goes Down Fast/D1 - Road Test
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NO -- Go to D4. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D4 - Inspect For Brake System Leaks
D4 - Inspect For Brake System Leaks ^ Perform Hydraulic Leak Test -- Pinpoint Test Q. See: Pinpoint Tests/Q - Hydraulic Leak Test ^ Does system leak? YES -- Service as necessary. Add fluid and bleed system. Repeat test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 - Road Test NO -- Go to D5. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D5 - Brake Master Cylinder Bypass Test
D5 - Brake Master Cylinder Bypass Test ^ Perform Brake Master Cylinder Bypass Condition Check -- Pinpoint Test R. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check ^ Is test OK? YES -- System OK. NO -- Replace damaged parts. Add fluid and bleed system. Repeat Test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 Road Test
E1 - Road Test ^ Check if condition occurs during actual stopping application by depressing the brake pedal while the vehicle is moving. ^ Does condition occur when vehicle is moving? YES -- Go to E2. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E2 - Recheck Brake System Leaks NO -- Condition occurs only when vehicle is stationary. Normal condition. No action required.
E2 - Recheck Brake System Leaks ^ Perform Hydraulic Leak Test -- Pinpoint Test QSee: Pinpoint Tests/Q - Hydraulic Leak Test. ^ Does system leak? YES -- Service as necessary, add fluid and bleed system. Repeat Test E1. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E1 - Road Test NO -- GO to E3. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E3 - Master Cylinder Bypass Test
E3 - Master Cylinder Bypass Test ^ Perform Brake Master Cylinder Bypass Condition Check -- Pinpoint Test R. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check ^ Is test OK? YES -- System OK. NO -- Replace damaged parts, add fluid and bleed system. Repeat Test E1. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E1 - Road Test
F1 - Brake Pedal Check ^ Statically apply brake pedal. ^ Road test vehicle only if condition cannot be verified in shop.
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^ Does brake pedal operate properly? YES -- Vehicle OK. NO -- Go to F2. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F2 - Brake Pedal Reserve Check
F2 - Brake Pedal Reserve Check ^ Key ON, engine running at idle with transmission in PARK or NEUTRAL. ^ Depress brake pedal lightly three or four times. ^ Wait 15 seconds to allow the vacuum to replenish. ^ Push down on brake pedal until it stops moving downward or an increased resistance to the brake pedal travel occurs. NOTE: This increased resistance may feel like the pedal has bottomed out. ^ Hold the brake pedal in the applied position while increasing the engine speed to 2000 rpm. ^ Release the accelerator pedal. ^ Does the brake pedal move downward as engine speed returns to normal? YES -- Go to F3. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F3 - Brake Fluid Level Check NO -- Check vacuum to power brake booster.
F3 - Brake Fluid Level Check ^ Check brake fluid level. ^ Is brake fluid level within specifications? YES -- Go to F4. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F4 - Filler Cap Vent Check NO -- Check brake master cylinder reservoir sealing points. Add fluid and Bleed system.
F4 - Filler Cap Vent Check ^ Check if brake master cylinder filler cap vent holes are clogged or dirty. ^ Are holes clogged or dirty? YES -- Clean as necessary. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 - Brake Pedal Check NO -- Go to F5. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F5 - Bleed Brake System
F5 - Bleed Brake System ^ Bleed brake system. ^ Has the condition been corrected? YES -- Vehicle OK. NO -- Go to F6. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F6 - Front Wheel Bearing Adjustment
F6 - Front Wheel Bearing Adjustment ^ Check front wheel bearings for proper adjustment. ^ Are bearings properly adjusted?
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YES -- Check rear brake adjustment and adjust if necessary. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 Brake Pedal Check NO -- Adjust front wheel bearings. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 - Brake Pedal Check
G1 - Tire Check ^ Check tires for uneven wear and correct pressure. ^ Is there a wear or pressure concern? YES -- Correct tire concern. NO -- Go to G2. See: Pinpoint Tests/G - Brakes Lockup When Applied/G2 - Brake Shoe and Lining Check
G2 - Brake Shoe and Lining Check ^ Inspect brake shoe and linings for contamination, correct installation, damage, correct size and type. ^ Is there a brake shoe and lining concern? YES -- Repair or replace brake shoe and lining. NO -- GO to G3. See: Pinpoint Tests/G - Brakes Lockup When Applied/G3 - Parking Brake Check
G3 - Parking Brake Check ^ Inspect parking brake components for damage or seized condition. ^ Is there a parking brake concern? YES -- Correct parking brake concern. NO -- Go to G4. See: Pinpoint Tests/G - Brakes Lockup When Applied/G4 - Wheel Bearing Check
G4 - Wheel Bearing Check ^ Raise vehicle enough to relieve weight on tires. ^ Pull alternately on front and rear of each tire to check for loose or damaged wheel bearings. ^ Is there a wheel bearing concern? YES -- Correct the wheel bearing concern. NO -- Go to G5. See: Pinpoint Tests/G - Brakes Lockup When Applied/G5 - Power Brake Booster Push Rod Check
G5 - Power Brake Booster Push Rod Check ^ Support the brake master cylinder (2140) and remove the brake master cylinder mounting nuts. ^ Position the brake master cylinder out of the way.
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Power Brake Booster Push Rod Adjustment Gauge ^ With a shop-fabricated gauge, check the power brake booster push rod adjustment. ^ The exposed end of the power brake booster push rod should be within 24.89-25.27mm (0.980-0.995 in.) of the brake master cylinder mounting surface on the power brake booster. ^ Does the power brake booster push rod require adjustment? YES -- Adjust as necessary. NO -- Go to G6. See: Pinpoint Tests/G - Brakes Lockup When Applied/G6 - ABS Check
G6 - ABS Check ^ Perform the appropriate diagnostic tests to check for defective dump valve. ^ Is there an anti-lock brake system concern? YES -- Repair or Replace the worn or damaged anti-lock brake system component. NO -- To check for possible missed symptoms, Go to G1. See: Pinpoint Tests/G - Brakes Lockup When Applied/G1 - Tire Check
H1 - Rough Road Test ^ Road test vehicle under rough road conditions. ^ Apply brakes slowly. ^ Are brakes good? YES -- Vehicle OK. NO -- Go to H2. See: Pinpoint Tests/H - Excessive and/or Erratic Pedal Travel/H2 - Wheel Bearing Check
H2 - Wheel Bearing Check ^ Check for loose front wheel bearings. ^ Are front wheel bearings loose? YES -- Replace front wheel bearing if damaged. Tighten front wheel bearing assembly to specification. Repeat H1. See: Pinpoint Tests/H Excessive and/or Erratic Pedal Travel/H1 - Rough Road Test NO -- Check front disc brake rotor for thickness variances.
J - Brakes Drag ^ Road test vehicle and apply brakes.
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^ Are brakes functional? YES -- Vehicle OK. NO -- Check power brake vacuum booster push rod. Repeat J1.
K1 - Road Test ^ With standard wheels and tires installed, road test the vehicle and verify the condition. ^ Do the front brakes chirp, shudder or vibrate? YES -- If shudder or vibration occurs, Go to K2. See: Pinpoint Tests/K - Brake Shudder/K2 - Apply Parking Brake NO -- A front brake chirp is normal condition. No repair required.
K2 - Apply Parking Brake ^ Lightly apply the parking brake while road testing the vehicle. ^ Does the vehicle shudder or vibrate when braking? YES -- Check the rear brakes. Go to K4. See: Pinpoint Tests/K - Brake Shudder/K4 - Refinish Drum Brakes NO -- Check the front brakes. Go to K3. See: Pinpoint Tests/K - Brake Shudder/K3 - Resurface Disc Brakes
K3 - Resurface Disc Brakes ^ Resurface front disc brake rotors and road test vehicle. ^ Does the condition persist? YES -- Replace front disc brake rotors. NO -- Brakes check OK.
K4 - Refinish Drum Brakes ^ Refinish brake drums and road test vehicle. ^ Does the condition persist? YES -- Replace brake drums. Repeat K1. See: Pinpoint Tests/K - Brake Shudder/K1 - Road Test NO -- Brakes check OK.
L - Excessive Brake Pedal Effort ^ Detach booster push rod from brake pedal pin and depress brake pedal fully. ^ Has condition been corrected? YES -- Check power brake booster vacuum availability. NO -- Service or Replace brake pedal linkage. Verify system OK.
M1 - Check Pedal Noise ^ Run engine at fast idle for 10 seconds or longer. Apply brake pedal and listen for noise. Compare results with known good system. ^ Was a noise present? YES -- Go to M2. See: Pinpoint Tests/M - Brake Noise/M2 - Push Rod Adjustment
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NO -- Vehicle OK.
M2 - Push Rod Adjustment
Power Brake Booster Push Rod Adjustment Gauge ^ Check and adjust power brake booster push rod ^ Is push rod OK? YES -- Bleed brake system. NO -- Replace power brake booster. Repeat Step M1. See: Pinpoint Tests/M - Brake Noise/M1 - Check Pedal Noise
N1 - Check Brake Pedal Return ^ Run engine at fast idle while making several brake applications. Pull brake pedal rearward with approximately 44.5N (10 lbs.) force. Release the brake pedal and measure the distance to the toe board. Make a hard brake application. Release the brake pedal and measure the brake pedal to toe board distance. The brake pedal should return to its original position. ^ Did brake pedal return to original position? YES -- Vehicle OK. NO -- Go to N2. See: Pinpoint Tests/N - Slow or Incomplete Brake Pedal Return/N2 - Check Brake Pedal Binding
N2 - Check Brake Pedal Binding ^ Check brake pedal to be sure it is operating freely. ^ Is the brake pedal operating freely? YES -- Replace power brake booster. NO -- Correct any sticking or binding. Repeat N2.
P - Vibration, Pedal Pumping, Low Pedal, Brake Chatter ^ Perform road tests and static tests to isolate trouble to the front, rear or parking brake system. ^ Has the condition been isolated? YES -- Repair, replace or adjust components of system as necessary. NO -- Repeat P1.
Q1 - Check For Leaks
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^ Apply the brakes and check for leaks. ^ Are any leaks found? YES -- Replace leaking parts as required. NO -- Go to Q2. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q2 - Rear Brake Leak Check
Q2 - Rear Brake Leak Check ^ Inspect all rear wheel cylinders or rear disc brake calipers (2552) for leaks. ^ Do rear wheel cylinders or rear disc brake calipers check OK? YES -- Go to Q3. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q3 - Front Brake Leak Check NO -- Replace or rebuild rear wheel cylinders or rear disc brake calipers as required.
Q3 - Front Brake Leak Check ^ Inspect front disc brake calipers (2B120) for leaks. ^ Do front disc brake calipers check OK? YES -- Go to Q4. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q4 - Master Cylinder Leak Check NO -- Replace or rebuild front disc brake calipers as required. Retest.
Q4 - Master Cylinder Leak Check ^ Disconnect the brake master cylinder connector tubes from the brake master cylinder. ^ Plug the output ports using the appropriate size flared tube type plugs. ^ Push down hard on the brake pedal. ^ Does the brake pedal slowly move downward? YES -- Replace or rebuild the brake master cylinder as required. NO -- Hydraulic system checks OK.
R1 - Fluid Level Check ^ Check the fluid level in the brake master cylinder reservoir. ^ Is the reservoir low or empty? YES -- Fill the brake master cylinder reservoir to the correct level. Go to R2. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R2 - Fluid Level Check, Brakes Applied NO -- Go to R2. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R2 - Fluid Level Check, Brakes Applied
R2 - Fluid Level Check, Brakes Applied ^ Apply brakes very slowly several times while observing the brake fluid level in the brake master cylinder reservoir. NOTE: Brake master cylinder bypass typically occurs when the brakes are applied very slowly and line pressures are low. A "hard" application can flare the internal lip seals out and result in a passing test where the concern may in fact be valid. ^ Does the level remain the same? YES -- Go to R3. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R3 - Wheel Turning Torque Check, Front
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Wheels NO -- Brake master cylinder checks OK.
R3 - Wheel Turning Torque Check, Front Wheels ^ Place transmission in NEUTRAL. ^ Raise front wheels off of ground. ^ Apply 445 N (100 lbs) evenly over a period of 30 seconds to the brakes and hold for approximately 15 seconds. ^ While holding brakes, exert 101 N (75 lbs) force to front wheels. ^ Does either wheel rotate? YES -- Service brake master cylinder as required. NO -- Front chamber of brake master cylinder checks OK. Go to R4. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R4 - Wheel Turning Torque Check, Rear Wheels
R4 - Wheel Turning Torque Check, Rear Wheels ^ Place transmission in NEUTRAL. ^ Raise rear wheels off of ground. ^ Apply 445 N (100 lbs) evenly over a period of 30 seconds to the brakes and hold for approximately 15 seconds. ^ While holding brakes, exert 101 N (75 lbs) force to rear wheels. ^ Does either wheel rotate? YES -- Service brake master cylinder as required. NO -- Rear chamber of brake master cylinder checks OK.
S1 - Vacuum Check ^ Disconnect vacuum booster hose from booster. ^ Connect Rotunda(r) Vacuum/Pressure Tester 059-00008 or equivalent to the vacuum hose with a T-fitting. ^ Key on, engine running. Allow engine to reach normal operating temperature. ^ Record the vacuum reading. ^ Is the vacuum reading at least 51-64 kPa (15-19 in-Hg)? YES -- Go to S2. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S2 - System Inspection NO -- Locate and repair source of low vacuum.
S2 - System Inspection ^ Key OFF. ^ Reconnect the vacuum line. ^ Inspect power brake booster check valve, rubber grommet and all vacuum plumbing for cracks, holes, bad connections or missing clamps. ^ Push down on brake pedal and hold. ^ Key ON, engine running.
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^ Does the brake pedal move downward when the engine is started? YES -- Vacuum system is OK. NO -- Go to S3. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S3 - Component Isolation Check
S3 - Component Isolation Check ^ Key OFF. ^ Reconnect the vacuum gauge to the same point as in Step S1, but leave the rest of the system connected. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S1 - Vacuum Check ^ Key ON, engine running at idle until vacuum reaches 51-64 kPa (15-19 in-Hg). ^ Key OFF. ^ Observe vacuum gauge for 1 minute. ^ Does vacuum pressure drop more than 3.4 kPa (1 in-Hg)? YES -- Disconnect each component one at a time and Repeat the above test procedures in until the leaking component is found. Plug the disconnected vacuum line while performing the test procedures. Repair or Replace as required. NO -- GO to S4. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S4 - Booster Leak Check
S4 - Booster Leak Check ^ Key ON. ^ Run engine until vacuum reaches 51-64 kPa (15-19 in-Hg). ^ Key OFF. ^ Push down on the brake pedal and hold for a few seconds and release. ^ Does the vacuum drop to 0 kPa (0 in-Hg)? YES -- Replace or Rebuild power brake booster as required. NO -- System checks OK. Remove vacuum gauge and reconnect all vacuum lines.
T1 - Fluid Level Check ^ Check fluid level in brake master cylinder reservoir. ^ Is fluid level in brake master cylinder reservoir full? YES -- Go to T2. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T2 - Fluid Level Condition NO -- Low or empty brake master cylinder reservoir with no brake warning indicator. Replace brake master cylinder reservoir.
T2 - Fluid Level Condition ^ Apply and release brake pedal one full stroke. Observe reservoir fluid level as brake pedal is released. ^ Does fluid level change? YES -- External leak outside of the brake master cylinder. Repair leak. NO -- Go to T3. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T3 - Master Cylinder Condition
T3 - Master Cylinder Condition
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^ Wipe off exterior of brake master cylinder, brake master cylinder filler cap (2162) and gasket with clean cloth. ^ Road test vehicle and pump brakes. ^ Check if brake master cylinder exterior is dry or wet. ^ Check for fluid from bore end of power brake booster at dash. ^ Is brake master cylinder dry? YES -- Go to T4. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T4 - Brake Pedal Condition Check NO -- External leak in brake master cylinder. Repair brake master cylinder.
T4 - Brake Pedal Condition Check ^ Apply pressure to brake pedal one full stroke and release, repeat 3 more cycles. ^ Does brake pedal go down 3.175mm (0.125 inch) each time? YES -- Check entire brake system for major leak. Repair as required. NO -- Brake master cylinder OK.
Road Test ROAD TEST Perform a road test to compare actual vehicle braking performance with the performance standards expected by the driver. The ability of the test driver to make valid comparisons and detect performance deficiencies will depend on experience. The driver should have a thorough knowledge of brake system operation and accepted general performance guidelines in order to make good comparisons and detect performance concerns. Select a road that will be reasonably smooth and level. NOTE: Gravel or bumpy roads are not suitable because the surface does not allow the tires to grip the road equally. Crowned roads should be avoided because of the large amount of weight shifted to the low set of wheels on this type of road. Once the route is established and consistently used, the road surface variable can be eliminated from the test results. Before a road test, get a complete description of the customer concerns or suspected condition. From the description, your experience will allow you to match possible causes with symptoms. Certain components will be tagged as possible suspects while others will be eliminated by the evidence. More importantly, the customer's description can reveal unsafe conditions which should be checked or corrected before the road test. The description will also help form the basic approach to the road test by narrowing the problem to specific components, vehicle speed or conditions. Begin the road test with a general brake performance check. Keeping the description in mind, test the brakes at different vehicle speeds using both light and heavy pedal pressure. To determine if the problem is in the front or rear braking system, first use the service brake pedal, then use the parking brake. If the condition (i.e., pull, vibration, pulsation) occurs only with the parking brake, the problem is in the rear system. If the condition occurs when the service brake pedal is pressed, the problem is in the front system. Avoid locking the brakes and sliding the tires. Locked brakes and sliding tires do not indicate brake efficiency: A heavily braked and turning wheel will stop the vehicle in less distance than locked brakes. If the problem becomes evident during this check, make sure it fits the description given before the road test. If the problem is not evident, attempt to duplicate the condition using the information from the description. If a concern exists, go to Diagnosis by Symptom in order to isolate it to a specific sub-system and condition description. See: Diagnosis By Symptom From this description, a list of possible causes can be used to further narrow the cause to a specific component or condition.
Cleaning and Inspection NOTE: If dirt is found in any part of the hydraulic system, flush the entire system with clean isopropyl alcohol. 1. Clean all brake cylinder parts in clean isopropyl alcohol or use the Rotunda Brake Parts Washer 065-00016 or equivalent. 2. Inspect all parts for wear or damage. 3. Check the cylinder bore for rust, scores, or other damage.
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4. Be sure the bleeder screw passage is clean and open. 5. Replace all parts that are worn or damaged.
With Antilock Brakes For Antilock Brake System Testing and Inspection Procedures, go to Antilock Brake System/Testing and Inspection. See: Antilock Brakes / Traction Control Systems/Testing and Inspection
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Brakes and Traction Control: Testing and Inspection Inspection and Verification (Start Testing Here) 1. Visually examine front and rear tires and wheel assemblies for damage such as uneven wear, tread washouts, or sidewall damage. Make sure the tires are of the same size, type and, where possible, same manufacturer. Any tire or wheel that is damaged should be replaced. 2. Wheels and tires must be cleared of any foreign matter, and tire pressures adjusted to the correct psi. 3. If tires exhibit uneven wear or feathering, the cause must be corrected. Check steering and suspension components for damage/wear and, if necessary, check and adjust steering alignment.
Brake Roughness, Vibration or Pulsation POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required. POSSIBLE SOURCE(S): ^ Excessive rotor runout, or thickness variation. ACTION(S) TO TAKE: ^ Service or replace rotor as required.
Brake Warning Light On POSSIBLE SOURCE(S): ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, check for leaks, and bleed system if required. POSSIBLE SOURCE(S): ^ Parking brake applied or not returning completely. ACTION(S) TO TAKE: ^ Release parking brake. POSSIBLE SOURCE(S): ^ Shorted light circuit. ACTION(S) TO TAKE: ^ Correct short in warning circuit. POSSIBLE SOURCE(S): ^ Damaged fluid level switch or float assembly. ACTION(S) TO TAKE: ^ Replace plastic reservoir assembly. POSSIBLE SOURCE(S): ^ Differential pressure switch shuttled due to leakage in hydraulic circuit or damaged differential switch. ACTION(S) TO TAKE: ^ Repair leakage in hydraulic circuit or replace combination valve. POSSIBLE SOURCE(S): ^ Anti-Lock light does self check. ACTION(S) TO TAKE: ^ Refer to Anti-lock Brakes. See: Antilock Brakes / Traction Control Systems/Testing and Inspection/Testing and Inspection Procedures/Displaying & Reading Trouble Codes
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POSSIBLE SOURCE(S): ^ Damaged combination valve. ACTION(S) TO TAKE: ^ Replace as required.
Brakes Drag, Slow or Incomplete Release POSSIBLE SOURCE(S): ^ Parking brake control or parking brake rear cable and conduits (2A635) binding. ACTION(S) TO TAKE: ^ Repair, lubricate, or replace parts as required. POSSIBLE SOURCE(S): ^ Brake drum binding. ACTION(S) TO TAKE: ^ Repair, lubricate, or replace parts as required. POSSIBLE SOURCE(S): ^ Damaged front wheel bearing. ACTION(S) TO TAKE: ^ Check bearings for adjustment, wear, damage. Adjust bearings. POSSIBLE SOURCE(S): ^ Worn or damaged brake master cylinder. ACTION(S) TO TAKE: ^ Perform a master cylinder diagnosis test. Repair as required. POSSIBLE SOURCE(S): ^ Caliper slides binding. ACTION(S) TO TAKE: ^ Replace slide pins, clean grooves, lubricate slides. POSSIBLE SOURCE(S): ^ Brakes out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes POSSIBLE SOURCE(S): ^ Restriction in hydraulic system. ACTION(S) TO TAKE: ^ Inspect the hydraulic system, then repair or replace as required. POSSIBLE SOURCE(S): ^ Binding/seized rear wheel cylinders or caliper pistons. ACTION(S) TO TAKE: ^ Repair or replace as required.
Brakes Grab or Lock When Applied POSSIBLE SOURCE(S): ^ Tires worn or incorrect pressure. ACTION(S) TO TAKE: ^ Inflate tires to correct pressure. If tires have worn tread, replace them.
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POSSIBLE SOURCE(S): ^ Grease or fluid on linings, or damaged linings. ACTION(S) TO TAKE: ^ Inspect, repair, or replace lining in sets. Clean rotors. POSSIBLE SOURCE(S): ^ Improper size or type of linings. ACTION(S) TO TAKE: ^ Replace with correct brake linings in sets. POSSIBLE SOURCE(S): ^ Over-reaction of brake booster. ACTION(S) TO TAKE: ^ Check brake booster for over-reaction by comparing with a known quality vehicle. Replace brake booster if required. POSSIBLE SOURCE(S): ^ Lining sensitivity to moisture. ^ Other brake system components: - Loose or missing pins for caliper attachment. - Worn, damaged or dry wheel bearings. ACTION(S) TO TAKE: ^ Inspect, repair, replace or lubricate components if required POSSIBLE SOURCE(S): ^ RABS Valve: defective outlet (dump) valve. ACTION(S) TO TAKE: ^ Refer to Symptom Diagnosis, Symptom B -- first item only.
Brakes Pull to One Side POSSIBLE SOURCE(S): ^ Unequal air pressure in tires. ACTION(S) TO TAKE: ^ Inflate tires to correct pressure. POSSIBLE SOURCE(S): ^ Grease or fluid on linings. Glazed linings. ACTION(S) TO TAKE: ^ Clean, sand or replace linings. Clean drums or rotors. POSSIBLE SOURCE(S): ^ Loose or missing disc brake caliper pin. ACTION(S) TO TAKE: ^ Replace missing pin. POSSIBLE SOURCE(S): ^ Improper size or type of lining on one wheel. ACTION(S) TO TAKE: ^ Replace with correct brake linings in sets. POSSIBLE SOURCE(S): ^ Improper size wheel cylinder on one wheel. ACTION(S) TO TAKE: ^ Replace with correct wheel cylinder.
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POSSIBLE SOURCE(S): ^ Stuck or seized pistons in wheel cylinders or seized calipers. ACTION(S) TO TAKE: ^ Repair or replace wheel cylinders or calipers as required. POSSIBLE SOURCE(S): ^ Restricted brake lines or hoses. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE(S): ^ Other brake components. - Improper adjustment of drum brakes. - Improper positioning of disc brake shoe and lining in the caliper. - Fit of caliper shoes to knuckle. - Improperly adjusted, damaged or worn wheel bearings. - Distorted drum brake shoes. - Worn brake linings or scored rotor. - Missing, broken or stretched retracting or retaining springs and clips. ACTION(S) TO TAKE: ^ Inspect, adjust, repair or replace as required POSSIBLE SOURCE(S): ^ Suspension or steering. ACTION(S) TO TAKE: ^ Repair Suspension or steering as required.
Brakes Vibrate During Application POSSIBLE SOURCE(S): ^ Improperly lubricated wheel bearings. ACTION(S) TO TAKE: ^ Service as required. POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace as required. POSSIBLE SOURCE(S): ^ Binding caliper sliders. ACTION(S) TO TAKE: ^ Service as required.
Empty Reservoir POSSIBLE SOURCE(S): ^ Leaking brake master cylinder. ACTION(S) TO TAKE: ^ Reposition gasket and brake master cylinder. POSSIBLE SOURCE(S): ^ Leaking mounting grommets. ACTION(S) TO TAKE: ^ Replace grommets and brake master cylinder reservoir.
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POSSIBLE SOURCE(S): ^ Leaking components (lines, hoses, front disc brake calipers, rear wheel cylinder, etc.). ACTION(S) TO TAKE: ^ Repair as required. Bleed system as required.
Excessive Brake Lining Wear POSSIBLE SOURCE(S): ^ Improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required. POSSIBLE SOURCE(S): ^ Binding caliper sliders. ACTION(S) TO TAKE: ^ Service caliper sliders as required.
Excessive Brake Pedal Effort to Fully Apply Brakes POSSIBLE SOURCE(S): ^ Overloaded vehicle. ACTION(S) TO TAKE: ^ Lighten load and advise owner of correct load limits of vehicle. POSSIBLE SOURCE(S): ^ Insufficient vacuum to power brake booster. ACTION(S) TO TAKE: ^ Replace damaged or leaking vacuum booster hoses (2A047). POSSIBLE SOURCE(S): ^ Restricted air filter on brake pedal. ACTION(S) TO TAKE: ^ Clean or replace filter. POSSIBLE SOURCE(S): ^ Booster and brake pedal linkage binding caused by worn bushings or corrosion. ACTION(S) TO TAKE: ^ Replace worn bushings or clean and lubricate linkage. POSSIBLE SOURCE(S): ^ Worn or damaged power brake booster. ACTION(S) TO TAKE: ^ Replace power brake booster. POSSIBLE SOURCE(S): ^ Brake lining worn, glazed, contaminated or improper type. ACTION(S) TO TAKE: ^ Replace brake lining in axle sets. POSSIBLE SOURCE(S): ^ Rear brake shoe and lining improperly installed. ACTION(S) TO TAKE: ^ Reposition brake shoes properly and eliminate any binding.
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POSSIBLE SOURCE(S): ^ Seized wheel cylinder pistons in rear wheel cylinders or front disc brake calipers. ^ Restricted brake lines or hoses. ACTION(S) TO TAKE: ^ Repair or replace as required.
With Rear Anti-Lock Brakes POSSIBLE SOURCE: ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, bleed system, check for leaks. POSSIBLE SOURCE: ^ Worn or damaged RABS valve accumulator or outlet (dump) valve. ACTION(S) TO TAKE: ^ Refer to Diagnosis By Symptom Test C. See: Antilock Brakes / Traction Control Systems/Testing and Inspection/Testing and Inspection Procedures/Diagnosis By Symptom/Symptom Diagnosis Procedures/Symptom C: Hard or Soft Brake Pedal
POSSIBLE SOURCE: ^ Brake drums out of adjustment.
ACTION(S) TO TAKE: ^ Adjust rear brakes.
POSSIBLE SOURCE: ^ Front wheel bearing out of adjustment.
ACTION(S) TO TAKE: ^ Adjust front wheel bearings.
POSSIBLE SOURCE: ^ Brake master cylinder or booster dash unit mounting loose.
ACTION(S) TO TAKE: ^ Tighten nuts and bolts as required.
POSSIBLE SOURCE: ^ Disc brake caliper attachment loose.
ACTION(S) TO TAKE: ^ Replace or tighten as required.
POSSIBLE SOURCE: ^ Worn or damaged brake shoe adjusting lever cables (2A178).
ACTION(S) TO TAKE: ^ Remove drum and check lining for proper adjustment. Replace brake shoe adjusting lever cables.
POSSIBLE SOURCE: ^ Glazed, worn, scored or damaged brake linings.
ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings.
POSSIBLE SOURCE: ^ Drums out-of-round or rotors with excessive runout.
ACTION(S) TO TAKE: ^ Refinish, or replace if wear exceeds limits.
POSSIBLE SOURCE: ^ Front brake hose (2078) improperly positioned.
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ACTION(S) TO TAKE: ^ Check front brake hose for mis-position near heat source. Reposition as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. POSSIBLE SOURCE: ^ Reservoir cap vent hole clogged. ACTION(S) TO TAKE: ^ Service or replace brake master cylinder filler cap (2162) as required.
With 4 Wheel Anti-Lock Brakes POSSIBLE SOURCE: ^ Low fluid level. ACTION(S) TO TAKE: ^ Add fluid, bleed system, check for leaks (Brake Bleeding). POSSIBLE SOURCE: ^ Worn or damaged four wheel ABS hydraulic control unit. ACTION(S) TO TAKE: ^ Refer to Symptom C (Soft/Hard Pedal). POSSIBLE SOURCE: ^ Brake drums out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes. POSSIBLE SOURCE: ^ Front wheel bearing out of adjustment. ACTION(S) TO TAKE: ^ Adjust front wheel bearings. POSSIBLE SOURCE: ^ Brake master cylinder or booster dash unit mounting loose. ACTION(S) TO TAKE: ^ Tighten nuts and bolts as required. POSSIBLE SOURCE: ^ Disc brake caliper attachment loose. ACTION(S) TO TAKE: ^ Replace or tighten as required. POSSIBLE SOURCE: ^ Worn or damaged brake shoe adjusting lever cables. ACTION(S) TO TAKE: ^ Remove drum and check lining for proper adjustment. Replace brake shoe adjusting lever cables. POSSIBLE SOURCE: ^ Glazed, worn, scored or damaged brake linings. ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings.
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POSSIBLE SOURCE: ^ Drums out-of-round or rotors with excessive runout. ACTION(S) TO TAKE: ^ Refinish, or replace if wear exceeds limits. POSSIBLE SOURCE: ^ Front brake hose (2078) improperly positioned. ACTION(S) TO TAKE: ^ Check front brake hose for mis-position near heat source. Reposition as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. See: Brake Bleeding POSSIBLE SOURCE: ^ Reservoir cap vent hole clogged. ACTION(S) TO TAKE: ^ Service or replace brake master cylinder filler cap (2162) as required.
Excessive Pedal Travel/Brake Pedal Goes to Floor Consistently POSSIBLE SOURCE: ^ Hydraulic system. ACTION(S) TO TAKE: ^ Perform master cylinder diagnosis test. POSSIBLE SOURCE: ^ Brake drums out of adjustment, worn, bad wear pattern, or cracked drums. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE: ^ Loose or improper attachment of brake pedal, pedal support booster and brake master cylinder. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE: ^ External leak. ACTION(S) TO TAKE: ^ Repair as required. POSSIBLE SOURCE: ^ Air in system. ACTION(S) TO TAKE: ^ Bleed system. See: Brake Bleeding POSSIBLE SOURCE: ^ Insufficient brake pedal reserve. ACTION(S) TO TAKE: ^ Go to Test D.
Grinding Noise
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POSSIBLE SOURCE(S): ^ Improperly lubricated wheel bearings. ACTION(S) TO TAKE: ^ Service wheel bearings as required.
Groan, Roughness or Chatter at Wheel (Brakes Applied) POSSIBLE SOURCE(S): ^ Loose wheel lugnuts. ACTION(S) TO TAKE: ^ Tighten to 85-105 ft lb. Replace wheel if stud holes are elongated POSSIBLE SOURCE(S): ^ Worn, damaged, dry or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Inspect, lubricate or replace. POSSIBLE SOURCE(S): ^ Loose or worn front suspension components. ACTION(S) TO TAKE: ^ Inspect, repair or replace front suspension components as required. POSSIBLE SOURCE(S): ^ Brake drum cracked or out-of-round. ACTION(S) TO TAKE: ^ Replace drum if required. POSSIBLE SOURCE(S): ^ Disc brake caliper backing plate and anchor plate loose, or missing parts, also loose or bent dust shield. ACTION(S) TO TAKE: ^ Repair or replace parts as required. POSSIBLE SOURCE(S): ^ Excessive wear or lateral run-out of rotor. ACTION(S) TO TAKE: ^ Replace rotor. POSSIBLE SOURCE(S): ^ Worn tires. ACTION(S) TO TAKE: ^ Replace tires.
Low Pedal POSSIBLE SOURCE(S): ^ Hydraulic system. ACTION(S) TO TAKE: ^ Perform diagnosis. Repair as required. POSSIBLE SOURCE(S): ^ Front wheel bearings out of adjustment. ACTION(S) TO TAKE:
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Adjust front wheel bearings.
POSSIBLE SOURCE(S): ^ Brake drums out of adjustment, worn, bad wear pattern or cracked brake drums. ACTION(S) TO TAKE: ^ Adjust or replace as required. POSSIBLE SOURCE(S): ^ Loose or improper attachment of brake pedal, pedal support, power brake booster and brake master cylinder. ACTION(S) TO TAKE: ^ Repair or replace components as required.
Noise at Wheels -- Brakes Applied -- Squeak or Squeal POSSIBLE SOURCE(S): ^ Worn or scored brake drums and lining or front disc brake hub and rotors (1102). ACTION(S) TO TAKE: ^ Inspect, repair or replace as required. POSSIBLE SOURCE(S): ^ Burrs or rust on front disc brake caliper that would obstruct seating of shoe to front disc brake caliper. ACTION(S) TO TAKE: ^ Clean or deburr front disc brake caliper. POSSIBLE SOURCE(S): ^ Dirty, greased or glazed linings. ACTION(S) TO TAKE: ^ Clean or replace. POSSIBLE SOURCE(S): ^ Improper lining parts or loose rear brake adjustment. ACTION(S) TO TAKE: ^ Inspect for correct usage. If necessary replace with correct type in axle sets. POSSIBLE SOURCE(S): ^ Other brake system components. - Loose lining rivets. - Weak, damaged or incorrect brake shoe retracting springs (2296). - Loose or damaged shoe retaining pins, brake shoe retracting springs and clips. - Grooved backing plate ledges. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required.
Noise at Wheels -- Brakes Not Applied -- Squeak or Squeal POSSIBLE SOURCE(S): ^ Wheel covers improperly attached. ACTION(S) TO TAKE: ^ Seat covers with a rubber mallet. Repair flanges or replace cover. POSSIBLE SOURCE(S): ^ Loose wheel attaching lugnuts. ACTION(S) TO TAKE: ^ Tighten to proper 85-105 ft lb. Replace wheel if stud holes are damaged. POSSIBLE SOURCE(S):
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Worn, dry or improperly adjusted wheel bearings.
ACTION(S) TO TAKE: ^ Replace worn or damaged wheel bearings. Lubricate and adjust. POSSIBLE SOURCE(S): ^ Glazed linings -- adjustment too tight. ACTION(S) TO TAKE: ^ Remove glaze from linings. Adjust brakes properly. POSSIBLE SOURCE(S): ^ Other brake system components. - Stretched brake shoe retracting springs. - Bent or warped brake backing plate causing interference with brake drum. - Improper positioning of disc brake pad in front disc brake caliper. - Excessive runout of front disc brake rotor. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required.
Noise at Wheels When Brakes Applied/Scrape or Grind POSSIBLE SOURCE(S): ^ Worn brake linings, loose rivets or foreign material between lining and brake drum or front disc brake rotor. ACTION(S) TO TAKE: ^ Replace rear brake shoes and linings. Refinish or replace brake drums or front disc brake rotors if excessively scored POSSIBLE SOURCE(S): ^ Brake shoe interference with back of brake drum, shield-to-rotor clearance or binding at backing plate guide ledges. ACTION(S) TO TAKE: ^ Inspect. Replace as necessary. Lubricate. POSSIBLE SOURCE(S): ^ Other brake system components. - Warped or bent brake backing plate causing interference with brake drum. - Cracked brake drums or rotors. - Loose brake shoe hold down springs. ACTION(S) TO TAKE: ^ Inspect and repair as necessary POSSIBLE SOURCE(S): ^ Tires rubbing against chassis, body, or loose brake shoe hold down springs. ACTION(S) TO TAKE: ^ Inspect. Repair as necessary.
Noise at Wheels When Brakes Applied/Snap or Click POSSIBLE SOURCE(S): ^ Cracked welds at brake shoe web. ACTION(S) TO TAKE: ^ Replace rear brake shoe and lining in axle sets. POSSIBLE SOURCE(S): ^ Brake shoes binding at backing plate ledges. ACTION(S) TO TAKE: ^ Clean and lubricate ledges. POSSIBLE SOURCE(S):
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Machining marks on brake drums.
ACTION(S) TO TAKE: ^ Refinish, or replace brake drums. POSSIBLE SOURCE(S): ^ Backing plate ledges worn. ACTION(S) TO TAKE: ^ Replace brake backing plate and lubricate ledges POSSIBLE SOURCE(S): ^ Loose or missing disc brake pad anti-rattle clips (2B164). ACTION(S) TO TAKE: ^ Replace clips. POSSIBLE SOURCE(S): ^ Improper rotor finish after turning. ACTION(S) TO TAKE: ^ Refinish or replace front disc brake rotors (1125) POSSIBLE SOURCE(S): ^ Improper positioning, wear or damage of front disc brake caliper. ACTION(S) TO TAKE: ^ Inspect, repair or replace disc brake caliper(s).
Noise at Wheels, Brakes Not Applied/Growling, Click or Rattle POSSIBLE SOURCE(S): ^ Stones or foreign material trapped inside wheel covers. ACTION(S) TO TAKE: ^ Remove stones, etc. POSSIBLE SOURCE(S): ^ Loose wheel lugnuts. ACTION(S) TO TAKE: ^ Tighten to 85-105 ft lb. Replace wheel if stud holes are elongated. POSSIBLE SOURCE(S): ^ Damaged, worn, or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace as required.
Noise at Wheels, Brakes Not Applied/Squeaks, Squeals or Chatter POSSIBLE SOURCE(S): ^ Brake backing plate. - Loose or missing anti-rattle clips, or caliper pins. ACTION(S) TO TAKE: ^ Inspect, repair or replace as required. POSSIBLE SOURCE(S): ^ Drum brake linings/shoes loose or extra parts. ACTION(S) TO TAKE: ^ Inspect, remove or repair. POSSIBLE SOURCE(S):
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Worn, damaged or dry wheel bearings.
ACTION(S) TO TAKE: ^ Inspect, lubricate or replace. Adjust wheel bearings.
Parking Brake Will Not Hold POSSIBLE SOURCE(S): ^ Parking brake rear cable and conduit out of adjustment. ACTION(S) TO TAKE: ^ Adjust parking brake rear cable and conduits POSSIBLE SOURCE(S): ^ Brake drums out of adjustment. ACTION(S) TO TAKE: ^ Adjust rear brakes. POSSIBLE SOURCE(S): ^ Primary brake shoe parking brake lever link (2A642) or parking brake rear cable and conduits, release lever, clevis and ratchet binding, worn or damaged. ACTION(S) TO TAKE: ^ Repair or replace parking brake linkage or cables as required.
Parking Brake Will Not Release or Fully Return POSSIBLE SOURCE(S): ^ Manual release brake control components binding or damaged. ACTION(S) TO TAKE: ^ Repair or replace rear parking brake cable. POSSIBLE SOURCE(S): ^ Primary brake shoe parking brake lever link and parking brake rear cable and conduits binding. ACTION(S) TO TAKE: ^ Repair or replace as required. POSSIBLE SOURCE(S): ^ Worn or damaged rear brake components. ACTION(S) TO TAKE: ^ Check rear brake shoe retracting springs and rear parking brake cables. Repair as required. POSSIBLE SOURCE(S): ^ Parking brake improperly adjusted. ACTION(S) TO TAKE: ^ Adjust as required.
Vibration When Brakes Are Applied POSSIBLE SOURCE(S): ^ Loose lugnuts. ACTION(S) TO TAKE: ^ Tighten lugnuts to 85-105 ft lb. Replace rim if stud holes are elongated.
POSSIBLE SOURCE(S): ^ Cracked front disc brake rotors.
ACTION(S) TO TAKE:
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Replace front disc brake rotor.
POSSIBLE SOURCE(S): ^ Front disc brake rotors/brake drums out-of-round or improper machining. ACTION(S) TO TAKE: ^ Machine rotors or replace as required. POSSIBLE SOURCE(S): ^ Worn or improperly adjusted wheel bearings. ACTION(S) TO TAKE: ^ Adjust or replace wheel bearings as required POSSIBLE SOURCE(S): ^ Loose or worn front suspension components. ACTION(S) TO TAKE: ^ Tighten loose components. Replace worn or damaged components. POSSIBLE SOURCE(S): ^ Excessive radial or lateral run-out on wheel and tire. ACTION(S) TO TAKE: ^ Adjust or replace tire or wheel to eliminate excessive run-out on tire or wheel as required.
A1 - Inspect Tire Pressure ^ Measure air pressure in all four tires. ^ Is tire pressure within specifications? YES -- Go to A2. See: Pinpoint Tests/A - Brakes Pull or Drift/A2 - Check Caliper and Rear Wheel Cylinders NO -- Adjust tire pressure.
A2 - Check Caliper and Rear Wheel Cylinders ^ Check the front disc brake caliper pistons, pins or rear wheel cylinders (2261) for binding, leakage or sticking. ^ Do the front disc brake caliper pistons, pins or rear wheel cylinders bind or stick? YES -- Repair or replace components as necessary. NO -- Go to A3. See: Pinpoint Tests/A - Brakes Pull or Drift/A3 - Inspect Front Disc Brake Rotors and Brake Drums
A3 - Inspect Front Disc Brake Rotors and Brake Drums ^ Inspect the disc brake rotors and/or brake drums (1126) for excessive runout or damage. ^ Does excessive runout or damage exist? YES -- Repair or replace disc brake rotor or brake drum as necessary. NO -- Go to A4. See: Pinpoint Tests/A - Brakes Pull or Drift/A4 - Inspect Wheel Bearings
A4 - Inspect Wheel Bearings ^ Inspect front and rear wheel bearings for excessive end play or improper preload. ^ Does excessive end play or improper wheel bearing preload exist? YES -- Adjust wheel bearing preload or Replace wheel bearings. NO -- Inspect for and Repair hydraulic leaks. Retest system.
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B1 - Check Parking Brake Switch ^ With parking brake fully released, disconnect the parking brake switch at the parking brake control. ^ Did brake warning indicator light go out? YES -- Replace the parking brake switch. Retest. NO -- Go to B2. See: Pinpoint Tests/B - Brake Warning Indicator Always ON/B2 - Isolate Circuits, 531 (DG/R), 977 (P/W), and 162 (Lg/R)
B2 - Isolate Circuits, 531 (DG/R), 977 (P/W), and 162 (Lg/R) ^ With brake master cylinder reservoir fluid level OK, disconnect the brake master cylinder fluid level switch connector at the brake master cylinder reservoir (2K478). ^ Does the brake warning indicator light go out? YES -- Go to B3. See: Pinpoint Tests/B - Brake Warning Indicator Always ON/B3 - Test Brake Fluid Level Indicator Switch NO -- Service ground short in circuit 531 (DG/Y), 977 (P/W), or 162 (LG/R).
B3 - Test Brake Fluid Level Indicator Switch ^ With the brake master cylinder reservoir fluid level OK, disconnect the fluid level switch connector. At the reservoir side of the connector, test for a ground at Circuits 531 (DG/Y) and 512 (T/LG).
Fluid Level Switch Connector ^ In which circuit is ground detected? 531 - Replace the brake master cylinder reservoir. 512 - Service the ground short in circuit 512 (T/LG).
C1 - Isolate Vibration/Shudder ^ Determine if vibration/shudder is induced by the rear brakes by using the parking brake to slow the vehicle from approximately 80 to 56 km/h (50 to 35 mph). To use the parking brake: ^ Hold the release handle out, or press release button in, while applying the parking brake. ^ Is vibration/shudder present? YES -- Check the rear brakes. Go to C2 for disc brakes. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C2 - Resurface Disc Brakes Go to C3 for drum brakes. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C3 - Refinish Brake Drums NO -- Check the front brakes. Go to C2. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C2 - Resurface Disc Brakes
C2 - Resurface Disc Brakes ^ Resurface front disc brake rotors (1125) and road test vehicle. ^ Is shudder/vibration present? YES -- Go to C4. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C4 - Replace Disc Brake Pads
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NO -- Brake system repaired.
C3 - Refinish Brake Drums ^ Refinish brake drums and road test vehicle. ^ Is shudder/vibration present? YES -- Go to C5. See: Pinpoint Tests/C - Vibration When Brakes Are Applied/C5 - Replace Brake Shoes and Linings NO -- Brake system repaired.
C4 - Replace Disc Brake Pads ^ Replace disc brake pads and road test vehicle. ^ Is shudder/vibration present? YES -- Replace front disc brake rotors. NO -- Brake system repaired.
C5 - Replace Brake Shoes and Linings ^ Replace rear brake shoes and linings (2200) and road test vehicle. ^ Is shudder/vibration present? YES -- Determine which brake drum or rotor is at fault and replace. NO -- Brake system repaired.
D1 - Road Test ^ Road test vehicle only if condition cannot be verified in shop. ^ Statically depress brake pedal (2455). ^ Does brake pedal operate properly? YES -- Vehicle OK. NO -- Go to D2. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D2 - Check Brake Fluid Level
D2 - Check Brake Fluid Level ^ Check brake fluid level. ^ Is fluid level within specifications? YES -- Go to D3. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D3 - Pressurize System NO -- Check reservoir sealing points. Add fluid and Bleed system. Repeat test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 - Road Test
D3 - Pressurize System ^ Pump brake pedal rapidly (five times). ^ Does brake pedal maintain height throughout test? YES -- Check rear brake adjustment and adjust if necessary. If condition still exists, bleed system. Repeat test D1. See: Pinpoint Tests/D Brake Pedal Goes Down Fast/D1 - Road Test
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NO -- Go to D4. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D4 - Inspect For Brake System Leaks
D4 - Inspect For Brake System Leaks ^ Perform Hydraulic Leak Test -- Pinpoint Test Q. See: Pinpoint Tests/Q - Hydraulic Leak Test ^ Does system leak? YES -- Service as necessary. Add fluid and bleed system. Repeat test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 - Road Test NO -- Go to D5. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D5 - Brake Master Cylinder Bypass Test
D5 - Brake Master Cylinder Bypass Test ^ Perform Brake Master Cylinder Bypass Condition Check -- Pinpoint Test R. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check ^ Is test OK? YES -- System OK. NO -- Replace damaged parts. Add fluid and bleed system. Repeat Test D1. See: Pinpoint Tests/D - Brake Pedal Goes Down Fast/D1 Road Test
E1 - Road Test ^ Check if condition occurs during actual stopping application by depressing the brake pedal while the vehicle is moving. ^ Does condition occur when vehicle is moving? YES -- Go to E2. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E2 - Recheck Brake System Leaks NO -- Condition occurs only when vehicle is stationary. Normal condition. No action required.
E2 - Recheck Brake System Leaks ^ Perform Hydraulic Leak Test -- Pinpoint Test QSee: Pinpoint Tests/Q - Hydraulic Leak Test. ^ Does system leak? YES -- Service as necessary, add fluid and bleed system. Repeat Test E1. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E1 - Road Test NO -- GO to E3. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E3 - Master Cylinder Bypass Test
E3 - Master Cylinder Bypass Test ^ Perform Brake Master Cylinder Bypass Condition Check -- Pinpoint Test R. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check ^ Is test OK? YES -- System OK. NO -- Replace damaged parts, add fluid and bleed system. Repeat Test E1. See: Pinpoint Tests/E - Pedal Goes Down Slowly/E1 - Road Test
F1 - Brake Pedal Check ^ Statically apply brake pedal. ^ Road test vehicle only if condition cannot be verified in shop.
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^ Does brake pedal operate properly? YES -- Vehicle OK. NO -- Go to F2. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F2 - Brake Pedal Reserve Check
F2 - Brake Pedal Reserve Check ^ Key ON, engine running at idle with transmission in PARK or NEUTRAL. ^ Depress brake pedal lightly three or four times. ^ Wait 15 seconds to allow the vacuum to replenish. ^ Push down on brake pedal until it stops moving downward or an increased resistance to the brake pedal travel occurs. NOTE: This increased resistance may feel like the pedal has bottomed out. ^ Hold the brake pedal in the applied position while increasing the engine speed to 2000 rpm. ^ Release the accelerator pedal. ^ Does the brake pedal move downward as engine speed returns to normal? YES -- Go to F3. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F3 - Brake Fluid Level Check NO -- Check vacuum to power brake booster.
F3 - Brake Fluid Level Check ^ Check brake fluid level. ^ Is brake fluid level within specifications? YES -- Go to F4. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F4 - Filler Cap Vent Check NO -- Check brake master cylinder reservoir sealing points. Add fluid and Bleed system.
F4 - Filler Cap Vent Check ^ Check if brake master cylinder filler cap vent holes are clogged or dirty. ^ Are holes clogged or dirty? YES -- Clean as necessary. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 - Brake Pedal Check NO -- Go to F5. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F5 - Bleed Brake System
F5 - Bleed Brake System ^ Bleed brake system. ^ Has the condition been corrected? YES -- Vehicle OK. NO -- Go to F6. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F6 - Front Wheel Bearing Adjustment
F6 - Front Wheel Bearing Adjustment ^ Check front wheel bearings for proper adjustment. ^ Are bearings properly adjusted?
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YES -- Check rear brake adjustment and adjust if necessary. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 Brake Pedal Check NO -- Adjust front wheel bearings. Repeat test F1. See: Pinpoint Tests/F - Pedal Is Low or Feels Spongy/F1 - Brake Pedal Check
G1 - Tire Check ^ Check tires for uneven wear and correct pressure. ^ Is there a wear or pressure concern? YES -- Correct tire concern. NO -- Go to G2. See: Pinpoint Tests/G - Brakes Lockup When Applied/G2 - Brake Shoe and Lining Check
G2 - Brake Shoe and Lining Check ^ Inspect brake shoe and linings for contamination, correct installation, damage, correct size and type. ^ Is there a brake shoe and lining concern? YES -- Repair or replace brake shoe and lining. NO -- GO to G3. See: Pinpoint Tests/G - Brakes Lockup When Applied/G3 - Parking Brake Check
G3 - Parking Brake Check ^ Inspect parking brake components for damage or seized condition. ^ Is there a parking brake concern? YES -- Correct parking brake concern. NO -- Go to G4. See: Pinpoint Tests/G - Brakes Lockup When Applied/G4 - Wheel Bearing Check
G4 - Wheel Bearing Check ^ Raise vehicle enough to relieve weight on tires. ^ Pull alternately on front and rear of each tire to check for loose or damaged wheel bearings. ^ Is there a wheel bearing concern? YES -- Correct the wheel bearing concern. NO -- Go to G5. See: Pinpoint Tests/G - Brakes Lockup When Applied/G5 - Power Brake Booster Push Rod Check
G5 - Power Brake Booster Push Rod Check ^ Support the brake master cylinder (2140) and remove the brake master cylinder mounting nuts. ^ Position the brake master cylinder out of the way.
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Power Brake Booster Push Rod Adjustment Gauge ^ With a shop-fabricated gauge, check the power brake booster push rod adjustment. ^ The exposed end of the power brake booster push rod should be within 24.89-25.27mm (0.980-0.995 in.) of the brake master cylinder mounting surface on the power brake booster. ^ Does the power brake booster push rod require adjustment? YES -- Adjust as necessary. NO -- Go to G6. See: Pinpoint Tests/G - Brakes Lockup When Applied/G6 - ABS Check
G6 - ABS Check ^ Perform the appropriate diagnostic tests to check for defective dump valve. ^ Is there an anti-lock brake system concern? YES -- Repair or Replace the worn or damaged anti-lock brake system component. NO -- To check for possible missed symptoms, Go to G1. See: Pinpoint Tests/G - Brakes Lockup When Applied/G1 - Tire Check
H1 - Rough Road Test ^ Road test vehicle under rough road conditions. ^ Apply brakes slowly. ^ Are brakes good? YES -- Vehicle OK. NO -- Go to H2. See: Pinpoint Tests/H - Excessive and/or Erratic Pedal Travel/H2 - Wheel Bearing Check
H2 - Wheel Bearing Check ^ Check for loose front wheel bearings. ^ Are front wheel bearings loose? YES -- Replace front wheel bearing if damaged. Tighten front wheel bearing assembly to specification. Repeat H1. See: Pinpoint Tests/H Excessive and/or Erratic Pedal Travel/H1 - Rough Road Test NO -- Check front disc brake rotor for thickness variances.
J - Brakes Drag ^ Road test vehicle and apply brakes.
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^ Are brakes functional? YES -- Vehicle OK. NO -- Check power brake vacuum booster push rod. Repeat J1.
K1 - Road Test ^ With standard wheels and tires installed, road test the vehicle and verify the condition. ^ Do the front brakes chirp, shudder or vibrate? YES -- If shudder or vibration occurs, Go to K2. See: Pinpoint Tests/K - Brake Shudder/K2 - Apply Parking Brake NO -- A front brake chirp is normal condition. No repair required.
K2 - Apply Parking Brake ^ Lightly apply the parking brake while road testing the vehicle. ^ Does the vehicle shudder or vibrate when braking? YES -- Check the rear brakes. Go to K4. See: Pinpoint Tests/K - Brake Shudder/K4 - Refinish Drum Brakes NO -- Check the front brakes. Go to K3. See: Pinpoint Tests/K - Brake Shudder/K3 - Resurface Disc Brakes
K3 - Resurface Disc Brakes ^ Resurface front disc brake rotors and road test vehicle. ^ Does the condition persist? YES -- Replace front disc brake rotors. NO -- Brakes check OK.
K4 - Refinish Drum Brakes ^ Refinish brake drums and road test vehicle. ^ Does the condition persist? YES -- Replace brake drums. Repeat K1. See: Pinpoint Tests/K - Brake Shudder/K1 - Road Test NO -- Brakes check OK.
L - Excessive Brake Pedal Effort ^ Detach booster push rod from brake pedal pin and depress brake pedal fully. ^ Has condition been corrected? YES -- Check power brake booster vacuum availability. NO -- Service or Replace brake pedal linkage. Verify system OK.
M1 - Check Pedal Noise ^ Run engine at fast idle for 10 seconds or longer. Apply brake pedal and listen for noise. Compare results with known good system. ^ Was a noise present? YES -- Go to M2. See: Pinpoint Tests/M - Brake Noise/M2 - Push Rod Adjustment
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NO -- Vehicle OK.
M2 - Push Rod Adjustment
Power Brake Booster Push Rod Adjustment Gauge ^ Check and adjust power brake booster push rod ^ Is push rod OK? YES -- Bleed brake system. NO -- Replace power brake booster. Repeat Step M1. See: Pinpoint Tests/M - Brake Noise/M1 - Check Pedal Noise
N1 - Check Brake Pedal Return ^ Run engine at fast idle while making several brake applications. Pull brake pedal rearward with approximately 44.5N (10 lbs.) force. Release the brake pedal and measure the distance to the toe board. Make a hard brake application. Release the brake pedal and measure the brake pedal to toe board distance. The brake pedal should return to its original position. ^ Did brake pedal return to original position? YES -- Vehicle OK. NO -- Go to N2. See: Pinpoint Tests/N - Slow or Incomplete Brake Pedal Return/N2 - Check Brake Pedal Binding
N2 - Check Brake Pedal Binding ^ Check brake pedal to be sure it is operating freely. ^ Is the brake pedal operating freely? YES -- Replace power brake booster. NO -- Correct any sticking or binding. Repeat N2.
P - Vibration, Pedal Pumping, Low Pedal, Brake Chatter ^ Perform road tests and static tests to isolate trouble to the front, rear or parking brake system. ^ Has the condition been isolated? YES -- Repair, replace or adjust components of system as necessary. NO -- Repeat P1.
Q1 - Check For Leaks
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^ Apply the brakes and check for leaks. ^ Are any leaks found? YES -- Replace leaking parts as required. NO -- Go to Q2. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q2 - Rear Brake Leak Check
Q2 - Rear Brake Leak Check ^ Inspect all rear wheel cylinders or rear disc brake calipers (2552) for leaks. ^ Do rear wheel cylinders or rear disc brake calipers check OK? YES -- Go to Q3. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q3 - Front Brake Leak Check NO -- Replace or rebuild rear wheel cylinders or rear disc brake calipers as required.
Q3 - Front Brake Leak Check ^ Inspect front disc brake calipers (2B120) for leaks. ^ Do front disc brake calipers check OK? YES -- Go to Q4. See: Pinpoint Tests/Q - Hydraulic Leak Test/Q4 - Master Cylinder Leak Check NO -- Replace or rebuild front disc brake calipers as required. Retest.
Q4 - Master Cylinder Leak Check ^ Disconnect the brake master cylinder connector tubes from the brake master cylinder. ^ Plug the output ports using the appropriate size flared tube type plugs. ^ Push down hard on the brake pedal. ^ Does the brake pedal slowly move downward? YES -- Replace or rebuild the brake master cylinder as required. NO -- Hydraulic system checks OK.
R1 - Fluid Level Check ^ Check the fluid level in the brake master cylinder reservoir. ^ Is the reservoir low or empty? YES -- Fill the brake master cylinder reservoir to the correct level. Go to R2. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R2 - Fluid Level Check, Brakes Applied NO -- Go to R2. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R2 - Fluid Level Check, Brakes Applied
R2 - Fluid Level Check, Brakes Applied ^ Apply brakes very slowly several times while observing the brake fluid level in the brake master cylinder reservoir. NOTE: Brake master cylinder bypass typically occurs when the brakes are applied very slowly and line pressures are low. A "hard" application can flare the internal lip seals out and result in a passing test where the concern may in fact be valid. ^ Does the level remain the same? YES -- Go to R3. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R3 - Wheel Turning Torque Check, Front
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Wheels NO -- Brake master cylinder checks OK.
R3 - Wheel Turning Torque Check, Front Wheels ^ Place transmission in NEUTRAL. ^ Raise front wheels off of ground. ^ Apply 445 N (100 lbs) evenly over a period of 30 seconds to the brakes and hold for approximately 15 seconds. ^ While holding brakes, exert 101 N (75 lbs) force to front wheels. ^ Does either wheel rotate? YES -- Service brake master cylinder as required. NO -- Front chamber of brake master cylinder checks OK. Go to R4. See: Pinpoint Tests/R - Brake Master Cylinder Bypass Condition Check/R4 - Wheel Turning Torque Check, Rear Wheels
R4 - Wheel Turning Torque Check, Rear Wheels ^ Place transmission in NEUTRAL. ^ Raise rear wheels off of ground. ^ Apply 445 N (100 lbs) evenly over a period of 30 seconds to the brakes and hold for approximately 15 seconds. ^ While holding brakes, exert 101 N (75 lbs) force to rear wheels. ^ Does either wheel rotate? YES -- Service brake master cylinder as required. NO -- Rear chamber of brake master cylinder checks OK.
S1 - Vacuum Check ^ Disconnect vacuum booster hose from booster. ^ Connect Rotunda(r) Vacuum/Pressure Tester 059-00008 or equivalent to the vacuum hose with a T-fitting. ^ Key on, engine running. Allow engine to reach normal operating temperature. ^ Record the vacuum reading. ^ Is the vacuum reading at least 51-64 kPa (15-19 in-Hg)? YES -- Go to S2. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S2 - System Inspection NO -- Locate and repair source of low vacuum.
S2 - System Inspection ^ Key OFF. ^ Reconnect the vacuum line. ^ Inspect power brake booster check valve, rubber grommet and all vacuum plumbing for cracks, holes, bad connections or missing clamps. ^ Push down on brake pedal and hold. ^ Key ON, engine running.
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^ Does the brake pedal move downward when the engine is started? YES -- Vacuum system is OK. NO -- Go to S3. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S3 - Component Isolation Check
S3 - Component Isolation Check ^ Key OFF. ^ Reconnect the vacuum gauge to the same point as in Step S1, but leave the rest of the system connected. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S1 - Vacuum Check ^ Key ON, engine running at idle until vacuum reaches 51-64 kPa (15-19 in-Hg). ^ Key OFF. ^ Observe vacuum gauge for 1 minute. ^ Does vacuum pressure drop more than 3.4 kPa (1 in-Hg)? YES -- Disconnect each component one at a time and Repeat the above test procedures in until the leaking component is found. Plug the disconnected vacuum line while performing the test procedures. Repair or Replace as required. NO -- GO to S4. See: Pinpoint Tests/S - Excessive Pedal Effort, Vacuum Boost System/S4 - Booster Leak Check
S4 - Booster Leak Check ^ Key ON. ^ Run engine until vacuum reaches 51-64 kPa (15-19 in-Hg). ^ Key OFF. ^ Push down on the brake pedal and hold for a few seconds and release. ^ Does the vacuum drop to 0 kPa (0 in-Hg)? YES -- Replace or Rebuild power brake booster as required. NO -- System checks OK. Remove vacuum gauge and reconnect all vacuum lines.
T1 - Fluid Level Check ^ Check fluid level in brake master cylinder reservoir. ^ Is fluid level in brake master cylinder reservoir full? YES -- Go to T2. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T2 - Fluid Level Condition NO -- Low or empty brake master cylinder reservoir with no brake warning indicator. Replace brake master cylinder reservoir.
T2 - Fluid Level Condition ^ Apply and release brake pedal one full stroke. Observe reservoir fluid level as brake pedal is released. ^ Does fluid level change? YES -- External leak outside of the brake master cylinder. Repair leak. NO -- Go to T3. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T3 - Master Cylinder Condition
T3 - Master Cylinder Condition
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^ Wipe off exterior of brake master cylinder, brake master cylinder filler cap (2162) and gasket with clean cloth. ^ Road test vehicle and pump brakes. ^ Check if brake master cylinder exterior is dry or wet. ^ Check for fluid from bore end of power brake booster at dash. ^ Is brake master cylinder dry? YES -- Go to T4. See: Pinpoint Tests/T - Brake Fluid Loss, Brake Master Cylinder Internal Test OK/T4 - Brake Pedal Condition Check NO -- External leak in brake master cylinder. Repair brake master cylinder.
T4 - Brake Pedal Condition Check ^ Apply pressure to brake pedal one full stroke and release, repeat 3 more cycles. ^ Does brake pedal go down 3.175mm (0.125 inch) each time? YES -- Check entire brake system for major leak. Repair as required. NO -- Brake master cylinder OK.
Road Test ROAD TEST Perform a road test to compare actual vehicle braking performance with the performance standards expected by the driver. The ability of the test driver to make valid comparisons and detect performance deficiencies will depend on experience. The driver should have a thorough knowledge of brake system operation and accepted general performance guidelines in order to make good comparisons and detect performance concerns. Select a road that will be reasonably smooth and level. NOTE: Gravel or bumpy roads are not suitable because the surface does not allow the tires to grip the road equally. Crowned roads should be avoided because of the large amount of weight shifted to the low set of wheels on this type of road. Once the route is established and consistently used, the road surface variable can be eliminated from the test results. Before a road test, get a complete description of the customer concerns or suspected condition. From the description, your experience will allow you to match possible causes with symptoms. Certain components will be tagged as possible suspects while others will be eliminated by the evidence. More importantly, the customer's description can reveal unsafe conditions which should be checked or corrected before the road test. The description will also help form the basic approach to the road test by narrowing the problem to specific components, vehicle speed or conditions. Begin the road test with a general brake performance check. Keeping the description in mind, test the brakes at different vehicle speeds using both light and heavy pedal pressure. To determine if the problem is in the front or rear braking system, first use the service brake pedal, then use the parking brake. If the condition (i.e., pull, vibration, pulsation) occurs only with the parking brake, the problem is in the rear system. If the condition occurs when the service brake pedal is pressed, the problem is in the front system. Avoid locking the brakes and sliding the tires. Locked brakes and sliding tires do not indicate brake efficiency: A heavily braked and turning wheel will stop the vehicle in less distance than locked brakes. If the problem becomes evident during this check, make sure it fits the description given before the road test. If the problem is not evident, attempt to duplicate the condition using the information from the description. If a concern exists, go to Diagnosis by Symptom in order to isolate it to a specific sub-system and condition description. See: Diagnosis By Symptom From this description, a list of possible causes can be used to further narrow the cause to a specific component or condition.
Cleaning and Inspection NOTE: If dirt is found in any part of the hydraulic system, flush the entire system with clean isopropyl alcohol. 1. Clean all brake cylinder parts in clean isopropyl alcohol or use the Rotunda Brake Parts Washer 065-00016 or equivalent. 2. Inspect all parts for wear or damage. 3. Check the cylinder bore for rust, scores, or other damage.
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4. Be sure the bleeder screw passage is clean and open. 5. Replace all parts that are worn or damaged.
With Antilock Brakes For Antilock Brake System Testing and Inspection Procedures, go to Antilock Brake System/Testing and Inspection. See: Antilock Brakes / Traction Control Systems/Testing and Inspection
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