GM Service Manual Online
For 1990-2009 cars only

Brake System Diagnosis Diagnostic Table

Symptom

Cause

Excessive brake pedal travel

    • Air in brake system
    • Leaking brake line or connection
    • Leaking piston seal
    • Leaking master cylinder
    • Uneven brake lining wear
    • Incorrect lining material
    • Excessive lateral runout
    • Faulty automatic adjuste
    • Missing or loose brake assembly attachments
    • Incorrect wheel bearing runout
    • Operator riding brake pedal
    • Improper booster pushrod length
    • Caliper not sliding freely

Brake pedal travel gradually increases

    • Leaking brake line or connection
    • Leaking piston seal
    • Leaking master cylinder
    • Restricted brake fluid passage or sticking wheel cylinder piston
    • Incorrect stoplamp switch adjustment
    • Operator riding brake pedal

Excessive brake pedal effort

    • Surface finish in rotors
    • Leaking vacuum system
    • Restricted air passage in power head
    • Damaged brake booster
    • Improperly assembled brake booster valving
    • Worn out brake lining
    • Incorrect lining material
    • Linings damaged by abusive
    • Restricted brake fluid passage
    • Brake pedal linkage interference or binding
    • Operator riding brake pedal
    • Sticking wheel cylinder or caliper pistons
    • Faulty proportioning valve

Excessive braking action

    • Contaminated brake lining
    • Linings damaged by abusive use
    • Leaking piston seal
    • Damaged brake booster
    • Improperly assembled brake booster valving
    • Incorrect lining material
    • Heat spotted or scored brake rotors
    • Weak or incorrect brake shoe retention springs
    • Incorrect stoplamp switch adjustment
    • Operator riding brake pedal
    • Improper booster pushrod length
    • Caliper not sliding freely
    • Faulty proportioning valve

Brakes slow to respond

    • Restricted air passage in power head
    • Contaminated or improper brake fluid
    • Leaking vacuum system
    • Improperly assembled brake booster valving
    • Brake pedal linkage interference or binding
    • Brake linkage interface or binding
    • Faulty proportioning valve
    • Damaged brake booster

Brakes slow to release

    • Brake pedal linkage interference or binding
    • Contaminated or improper brake fluid
    • Restricted air passage in power head
    • Damaged brake booster
    • Improperly assembled brake booster valving
    • Insufficient brake shoe guide lubricant
    • Restricted brake fluid passage or sticking wheel cylinder piston
    • Parking cable seized
    • Improper booster pushrod length
    • Sticking wheel cylinder or caliper pistons
    • Faulty proportioning valve

Brakes drag

    • Improperly assembled brake booster valving
    • Incorrect stoplamp switch adjustment
    • Brake pedal linkage interference or binding
    • Improper booster pushrod length
    • Faulty proportioning valve
    • Caliper not sliding freely
    • Sticking caliper pistons
    • Operator riding brake pedal
    • Parking brake cable seized
    • Improperly adjusted parking brake
    • Restricted brake fluid passage
    • Missing or loose brake assembly attachments
    • Faulty automatic adjusters
    • Damaged brake booster
    • Contaminated or improper brake fluid

Uneven braking action (side to side)

    • Contaminated brake lining
    • Incorrect front end alignment
    • Leaking brake line or connection
    • Leaking piston seal
    • Air to brake system
    • Worn out brake lining
    • Uneven brake lining wear
    • Incorrect lining material
    • Linings damaged by abusive use
    • Heat spotted or scored rotors
    • Faulty automatic adjusters
    • Missing or loose brake assembly attachments
    • Insufficient brake shoe guide lubricant
    • Restricted brake fluid passage
    • Loose front suspension attachments
    • Sticking caliper pistons
    • Faulty proportioning valve

Uneven braking action (front to back)

    • Worn out brake lining
    • Uneven brake lining wear
    • Incorrect lining material
    • Contaminated brake lining
    • Linings damaged by abusive use
    • Heat spotted rotors
    • Faulty automatic adjusters
    • Missing or loose brake assembly attachment
    • Restricted brake fluid passage or sticking wheel cylinder pisto
    • Parking brake cable seized
    • Operator riding brake pedal
    • Sticking caliper pistons
    • Faulty proportioner valve
    • Incorrect stoplamp switch adjustment

Scraping noise from brakes

    • Loose front suspension attachments
    • Caliper not sliding freely
    • Incorrect wheel bearing runout
    • Loose or missing brake assembly attachments
    • Linings damaged by abusive use
    • Contaminated brake lining
    • Uneven brake lining wear
    • Worn out brake lining

Brakes squeak during application

    • Insufficient brake shoe guide lubricant
    • Excessive lateral runout
    • Heat spotted or scored brake drum or rotors
    • Linings damaged by abusive use
    • Contaminated brake lining
    • Uneven brake lining wear
    • Operator riding brake pedal
    • Loose or missing brake assembly attachments
    • Linings damaged by abusive use
    • Incorrect lining material
 

Brakes pulsate (roughness)

    • Caliper not sliding freel
    • Improper rotor thickness variation
    • Incorrect lining material
    • Heat spotted rotors
    • Out-of-round brake drums
    • Excessive lateral runout
    • Missing or loose brake assembly attachments

Brakes groan at end of stop

    • Worn out brake lining
    • Uneven brake lining wear
    • Incorrect lining material
    • Contaminated brake lining
    • Linings damaged by abusive use
    • Heat spotted rotors
    • Missing or loose brake assembly attachments
    • Loose front suspension attachments
    • Operator riding brake pedal

BRAKE warning lamp glows

    • Leaking brake line or connection
    • Leaking piston seal
    • Leaking master cylinder
    • Contaminated or improper brake fluid
    • Improperly adjusted parking brake
    • Parking brake cable seized
    • Short to ground 1134