GMC 1986 P-Truck Service Manual page 426

5-6 BRAKES
DIAGNOSIS OF BRAKE SYSTEM (CONT.)
PROBLEM
Brakes Drag.
Brake tell-tale light
comes on.
Excessive Brake
Pedal Effort.
POSSIBLE CAUSE
1. Malfunctioning caliper assembly.
2. Contaminated or improper brake fluid.
3. Improperly adjusted parking brakes.
4. Restricted brake tube or hoses.
5. Malfunctioning proportioning valve.
6. Malfunctioning self adjusters.
7. Malfunctioning master cylinder.
8. Improperly adjusted master cylinder
pushrod.
1. Air in the brake system.
2. Malfunctioning master cylinder.
3. Contaminated or improper brake fluid.
4. Parking brake on or not fully released.
5. Worn out brake lining.
6. Incorrect wheel bearing adjustment.
7. Malfunctioning self adjusters.
8. Brake assembly attachments missing
or loose.
9. Improperly adjusted master cylinder
pushrod.
1. Loose or broken power steering pump
belt.
2. No fluid in the power steering reser­
voir.
3. Leaks at Hydro-Boost tube fittings.
4. External leakage at the accumulator.
5. Faulty booster piston seal causing
leakage at the booster flange vent.
6. Faulty booster input rod seal with
leakage at the input rod end.
7. Fautly booster cover seal with leakage
between the housing and cover.
8. Fautly booster spool plug seal.
CORRECTION
1. Check for frozen or sluggish pistons
and the lubrication of the retainer
bolts. Caliper should slide.
2. Repair as necessary.
3. Repair as necessary.
4. Check for collapsed rubber hoses or
damaged lines. Repair as necessary.
5. Replace or repair as necessary.
6. Repair as necessary.
7. Repair as necessary.
8. Adjust pushrod length.
1. Check fluid level. Check for leaks in
lines, wheel cylinders, or master cyl­
inder. Bleed the system.
2. Check for faulty metering valve, or
leaking. Repair as necessary.
3. Repair as necessary.
4. Check parking brake. Repair as nec­
essary.
5. Replace linings.
6. Repair as necessary.
7. Repair as necessary.
8. Replace or repair as necessary.
9. Adjust pushrod length.
1. Tighten or replace the belt.
2. Fill reservoir and check for external
leaks.
3. Tighten fittings or replace tube seats,
if faulty.
4. Replace seal and retainer.
5. Overhaul with new seal or input rod
and piston assembly.
6. Overhaul with new seal kit.
7. Overhaul with new seal kit.
8. Overhaul with spool plug seal kit.