GMC 1986 P-Truck Service Manual page 425

DIAGNOSIS OF BRAKE SYSTEM (CONT.)
PROBLEM
1. Worn out linings.
Brakes Squeak.
2. Glazed brake lining.
3. Heat spotted rotors or drums.
4. Weak or incorrect brake shoe retention
5. Contaminated brake linings.
6. Incorrect lining material.
7. Brake assembly attachments missing
8. Excessive brake lining dust.
1. Excessive rotor lateral runout.
Brake Pedal
Pulsates.
2. Rear drums out of round.
3. Heat spotted rotors or drums.
4. Incorrect wheel bearing adjustments.
5. Out of balance wheel assembly attach­
6. Brake assembly attachments missing
Excessive Pedal 1. Leaking vacuum system.
2. Malfunctioning power brake unit.
Effort.
3. Worn out linings.
4. Malfunctioning proportioning valve.
5. Incorrect lining material.
6. Incorrect wheel cylinder.
Excessive Pedal 1. Insufficient fluid in master cylinder res­
Travel.
2. Air in brake system.
3. Malfunctioning self adjusters.
4. Master cylinder.
5. Incorrect wheel bearing adjustment.
6. Improperly adjusted master cylinder
POSSIBLE CAUSE
springs.
or loose.
ments missing or loose.
or loose.
ervoir.
pushrod.
BRAKES 5-5
CORRECTION
1. Replace linings.
2. Replace linings.
3. Check per instructions. If within spec­
ifications machine the rotor or drum.
4. Replace with new retention springs.
5. Repair as necessary. Replace linings
in complete axle sets.
6. Replace with linings of correct mate­
rial.
7. Repair as necessary.
8. Clean dust from brake assembly.
1. Check per instructions. If within spec­
ifications machine the rotor.
2. Check per instructions. If within spec­
ifications machine the drum.
3. Check per instructions. If within spec­
ifications machine the rotor or drum.
4. Repair as necessary.
5. Repair as necesary.
6. Repair as necessary.
1. Repair as necessary.
2. Repair as necessary.
3. Replace linings.
4. Repair as necessary.
5. Replace with linings of correct mate­
rials.
6. Replace with corrrect size wheel cyl­
inder.
1. Fill reservoir with approved brake
fluid. Check for leaks and air in the
system. Check tell-tale light.
2. Check for leaks in lines, wheel cylin­
ders, or master cylinder. Bleed the
system.
3. Repair as necessary.
4. Replace or repair as necessary.
5. Repair as necessary.
6. Adjust master cylinder pushrod.