Brake System Diagnosis
Symptom
| Causes
|
Excessive Brake Pedal Travel
|
| • | Leaking brake line or connection. |
| • | Leaking piston or axle seal. |
| • | Leaking master cylinder (internal). |
| • | Contaminated or improper brake fluid. |
| • | Uneven brake lining wear. |
| • | Improper thickness variation in rotor. |
| • | Excessive lateral runout in rotor. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Improper rear brake adjustment. |
| • | Excessive vehicle loading. |
|
Brake Pedal Travel Gradually Increases
|
| • | Leaking brake line or connection. |
| • | Leaking master cylinder (internal). |
| • | Leaking ABS Modulator (Internal). |
| • | Restricted passage in the vacuum booster. |
| • | Damaged vacuum booster. |
| • | Restricted brake fluid passage. |
| • | Improper Rear Brake Adjustment. |
|
Excessive Brake Pedal Effort
|
| • | Leaking vacuum or booster system. |
| • | Restricted passage in the vacuum booster. |
| • | Damaged vacuum booster. |
| • | Incorrect brake lining material. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
| • | Restricted brake fluid passage. |
| • | Brake pedal linkage interference or binding. |
| • | Operator riding the brake pedal. |
| • | Restricted hydraulic line to the booster. |
| • | Excessive vehicle loading. |
|
Excessive Braking Action
|
| • | Leaking vacuum or booster system. |
| • | Restricted passage in vacuum booster. |
| • | Damaged vacuum booster system. |
| • | Uneven brake lining wear. |
| • | Incorrect brake lining material. |
| • | Brake lining damage by abuse. |
| • | Improper rotor or drum surface finish. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
|
Brakes Slow To Respond
|
| • | Contaminated or improper brake fluid. |
| • | Leaking vacuum or booster system. |
| • | Restricted passage in the vacuum booster. |
| • | Damaged vacuum booster. |
| • | Restricted brake fluid passage. |
| • | Brake pedal linkage interference or binding. |
| • | Sticking caliper or caliper pistons. |
| • | Restricted hydraulic line to the booster. |
|
Brakes Slow To Release
|
| • | Contaminated or improper brake fluid. |
| • | Restricted passage in the vacuum booster. |
| • | Damaged vacuum booster. |
| • | Restricted brake fluid passage. |
| • | Brake pedal linkage interference or binding. |
| • | Sticking caliper or caliper pistons. |
| • | Parking brake not releasing. |
| • | Caliper to knuckle clearance. |
|
Brakes Drag
|
| • | Contaminated or improper brake fluid. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Restricted brake fluid passage. |
| • | Improperly adjusted stoplamp switch. |
| • | Improperly adjusted cruise control vacuum dump. |
| • | Brake pedal linkage interference or binding. |
| • | Improperly adjusted parking brake. |
| • | Loose front suspension parts. |
| • | Operator riding the brake pedal. |
| • | Sticking caliper or caliper pistons. |
|
Uneven Braking Action (Side to Side)
|
| • | Contaminated or improper brake fluid. |
| • | Uneven brake lining wear. |
| • | Incorrect brake lining material. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Restricted brake fluid passage. |
| • | Incorrect front wheel alignment. |
| • | Incorrect tire pressure. |
| • | Loose front suspension parts. |
| • | Sticking caliper or caliper pistons. |
| • | Parking brake not releasing. |
| • | Caliper to knuckle clearance. |
|
Uneven Braking Action (Front to Rear)
|
| • | Leaking brake line or connection. |
| • | Leaking piston or axle seal. |
| • | Leaking master cylinder (internal). |
| • | Contaminated or improper brake fluid. |
| • | Uneven brake lining wear. |
| • | Incorrect brake lining material. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Restricted brake fluid passage. |
| • | Improperly adjusted parking brake. |
| • | Sticking caliper or caliper pistons. |
| • | Improper rear brake adjustment. |
| • | Excessive Vehicle Loading. |
|
Scraping Noise From Brakes
|
| • | Uneven brake lining wear. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Loose front suspension parts. |
|
Brakes Squeak Without Application
|
| • | Uneven brake lining wear. |
| • | Incorrect brake lining material. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
|
Brakes Squeak During Application
|
| • | Uneven brake lining wear. |
| • | Incorrect brake lining material. |
| • | Contaminated brake lining. |
| • | Brake lining damage by abuse. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
|
Brakes Chatter (Roughness)
|
| • | Improper thickness variation. |
| • | Excessive lateral runout. |
| • | Brake assembly attachments missing or loose (including splash
shield). |
| • | Loose front suspension parts. |
| • | Out-of-balance wheel assembly. |
| • | Improperly torqued wheel nuts. |
| • | Poor drum surface finish. |
|
Brakes Groan at End of Stop
| Brake lining damage by abuse.
|
Brake Warning Lamp ON
|
| • | Leaking brake line or connection. |
| • | Leaking piston or axle seal. |
| • | Leaking master cylinder (internal). |
| • | Contaminated or improper brake fluid. |
| • | Uneven brake lining wear. |
| • | Parking brake switch circuit grounded. |
| • | Parking brake not releasing. |
|
Premature Lining Wear Out
|
| • | Leaking brake line or connection. |
| • | Improperly adjusted stoplamp switch. |
| • | Improperly adjusted cruise control vacuum dump. |
| • | Brake pedal linkage interference or binding. |
| • | Out-of-balance wheel assembly. |
| • | Operator riding brake pedal. |
| • | Caliper to knuckle clearance. |
|
Parking Brake Won't Hold.
| Improperly adjusted parking brake.
|
Parking Brake Won't Release
|
| • | Parking brake cables frozen. |
| • | Parking brake cables corroded. |
|
Brake Pulsation
|
| • | Leaking brake line or connection. |
| • | Leaking piston or axle seal. |
| • | Incorrect lining material. |
| • | Contaminated brake lining. |
| • | Brake linings damaged by abuse. |
| • | Improper thickness variation. |
| • | Excessive lateral runout. |
| • | Out-of-balancer wheel assembly. |
| • | Improperly torqued wheel nuts. |
| • | Poor drum surface finish. |
|
Brake Pulls
|
| • | Leaking brake line or connection. |
| • | Leaking piston or axle seal. |
| • | Uneven brake lining wear. |
| • | Incorrect lining material. |
| • | Contaminated brake lining. |
| • | Brake linings damaged by abuse. |
| • | Improper rotor surface finish. |
| • | Incorrect front wheel alignment. |
| • | Incorrect tire pressure. |
| • | Loose front suspension parts. |
| • | Caliper to knuckle clearance. |
|
