14
DRUM BRAKE TROUBLESHOOTING
SYMPTOM
CAUSE
REMEDY
1. Low Pedal.
1.
Excessive clearance between
1.
Adjust brakes.
drums and linings.
2.
Automatic adjusters not
2.
Make several forward and
working.
reverse stops; if pedal does not
come up, repair automatic
adjusters.
3.
Bent or distorted brake shoes.
3.
Replace shoes and linings in axle
sets.
4.
Leak in hydraulic system.
4.
Refer to vehicle service manual.
5.
Air in hydraulic system.
5.
Bleed system; refer to vehicle
service manual.
6.
Low brake fluid.
6.
Fill master cylinder. If
necessary, bleed system. Refer
to vehicle service manual.
7.
Weak brake hoses.
7.
Refer to vehicle service manual.
2. Springy or spongy
1.
Bent or distorted brake shoes.
1.
Replace shoes and linings in
pedal.
axle sets.
2.
Shoes not centered in drums.
2.
Make certain shoe webs are
seated in tappet or piston slots.
3.
Cracked or thin drums.
3.
Replace drums in axle sets.
4.
Air in hydraulic systems.
4.
Bleed system; refer to vehicle
service manual.
5.
Weak brake hoses.
5.
Refer to vehicle service manual.
6.
Drums out of round.
6.
Refinish, or replace if wear
exceeds limits.
3. Hard pedal.
1.
Grease or brake fluid on linings.
1.
Replace grease seal, wheel
cylinder, or expander as
necessary. Replace brake shoes
in axle sets.
2.
Glazed linings.
2.
Sand lining surfaces or replace
shoes and linings in axle sets.
3.
Damaged or distorted shoes.
3.
Replace brake shoes in axle sets.
4.
Scored, barrel-shaped, or
4.
Refinish or replace drums in
bell-mounted drums.
axle sets.
5.
Defective master cylinder or
5.
Refer to vehicle service manual.
other brake system components.
4. Grabby brakes.
1.
Incorrect or distorted shoes.
1.
Replace with correct shoes in
axle sets.
2.
Incorrect linings or lining loose
2.
Replace with correct shoes
on shoes.
in axle sets.
3.
Grease or brake fluid on linings.
3.
Repair grease seal, wheel
cylinder, or expander as
necessary. Replace brake shoes
in axle sets.
4.
Shoes not centered in drums.
4.
Adjust steady post.
5.
Loose or distorted backing plate
5.
Tighten or replace backing plate
(dirtshield).
(dirtshield).
