GMC 4000 Series Service Manual page 209

Sec. 5A
Page 202
HYDRAULIC BRAKES
ALL BRAKES DRAG WHEN ADJUSTMENT IS KNOWN TO BE CORRECT (Cont'd.)
PROBABLE CAUSE
2. Improper fluid.
3. Compensating or bypass port of master
cylinder closed.
4. Use of inferior rubber parts.
ONE WHEEL DRAGS
PROBABLE CAUSE
1 . Weak or broken shoe retracting springs.
2. Brake shoe to drum clearance too small.
3. Loose wheel bearings.
4. Wheel cylinder piston cups swollen and d is­
torted or the piston stuck.
5. Pistons sticking in wheel cylinder.
6. Drum out-of-round.
7. Obstruction in line.
8. Distorted shoe.
9. Defective lining.
PULLS TO ONE SIDE
PROBABLE CAUSE
1. Grease or fluid soaked lining.
2. Loose wheel bearings,.loose packing plate on
rear axle or front axle or loose spring bolts.
3. Linings not of specified kind or primary and
secondary shoes reversed.
4. Tires not properly inflated or unequal wear of
tread. Different tread non-skid design.
5. Linings charred.
6. Water, mud, etc., in brakes.
7. Wheel cylinder sticking.
8. Weak or broken retracting springs.
9. Out-of-round drums.
G M C S E R V I C E M A N U A L
2. Replace rubber parts and fill with recom ­
3. Open by air or .015 wire. Remove any burr
4. Install proper parts.
1 .
2. Adjust.
3. Adjust wheel bearings.
4. Rebuild cylinders.
5. Clean or replace pistons; clean cylinder bore.
6. Grind or turn both front or rear drums.
7. Clean out or replace.
8. Replace.
9. Replace with specified lining.
1. Replace with new linings.
2. Adjust the wheel bearing, tighten the backing
plate on the rear and front axles and tighten
3. Install specified linings. Install shoes
correctly.
4. Inflate the tires to recommended p ressures.
Rearrange the tires so that a pair of non-skid
tread surfaces of sim ilar design and equal
wear will be installed on the front wheels, and
on the rear wheels.
5. Sand the surfaces of the lining.
6. Remove any foreign material from all of the
brake parts and inside of the drums. Lubricate
the shoe ledges and rear brake cable ramps.
7. Repair or replace wheel cylinder.
8. Check springs — replace bent, open-coiled or
cracked springs.
9. Resurface or replace drums in left- and right-
hand pairs (both front and both rear).
REMEDY
mended brake fluid.
in bore.
REMEDY
Replace the defective brake shoe springs and
lubricate the brake shoe ledges.
REMEDY
spring bolts.
another pair with like tread will be installed