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BRAKES-SERVICE
5-3
Condition
Possible Cause
Correction
PARKING BRAKES (Continued)
BRAKE WILL NOT HOLD
POWER BRAKES
DRAGGING BRAKES
(All
Wheels)
GRABBING BRAKES
(a) Improperly adjusted brake or cable.
(b) Broken or rusted brake cable.
(c) Worn brake lining.
(d) Ratchet or pedal mechanism worn.
(a) Brake shoes improperly adjusted.
(b) Brake pedal linkage binding.
(c) Excessive hydraulic seal friction.
(d) Compensator port plugged.
(e) Sticking valve plunger.
(f) Improper booster push rod length adjustment.
(9) Fluid cannot return to master cylinder.
(h) Parking brake not returning.
(i) Improperly staked valve sleeve.
(a) Grease or brake fluid on linings.
(b) Sticking actuating valve.
PEDAL
GOES TO
FLOOR (a) Self-adjusters not operating.
(or almost to floor)
(b) Air in hydraulic system.
(c) Hydraulic leak.
(d) Fluid low in master cylinder.
(e) Shoe hanging up on rough platform.
(f) Broken plunger stem.
HARD PEDAL (Power
Unit trouble)
(a) Faulty vacuum check valve.
(b) Collapsed or leaking vacuum hose.
(c)
Plugged vacuum fittings.
(d) Leaking vacuum chamber.
(e) Diaphragm assembly out of place in housing.
(f) Vacuum leak in forward vacuum housing.
SELF-APPLICATION OF
(a) Leak in rear housing.
BRAKES WHEN ENGINE (b) Diaphragm out of location in housings and al-
STARTS
lowing atmospheric pressure into rear chamber.
(c) Sticking or unseated actuating valve assembly.
GRUNTING NOISE
IN
BOOSTER ON
APPLICATION
(a) Air in hydraulic system.
(b) Lack of valve plunger lubrication.
(c) Fluid low in master cylinder.
(a) Adjust brakes and cable as necessary.
(b) Replace or clean and lubricate the brake.
(c) Replace brake lining.
(d) Replace pedal assembly.
(a) Adjust brakes.
(b) Free up linkage.
(c) Lubricate seal.
(d) Clean out master cylinder.
(e) Free up and lubricate valve plunger.
(f) Adjust push rod.
(9) Inspect pedal return and push rod adiustment.
(h) Free up as required.
(i) Replace valve assembly.
(a) Inspect for a leak and replace lining as re-
(b) Free up valve.
quired.
(a) Inspect self-adiuster operations.
(b) Bleed brakes.
(c) Locate and correct leak.
(d) Add brake fluid.
(e) Smooth and lubricate platforms.
(f) Replace valve plunger assembly.
(a) Replace check valve.
(b) Replace hose.
(c) Clean out fittings.
(d) Locate and correct leak.
(e) Position diaphragm.
(f) Locate and correct leak.
(a) Locate and correct leak.
(b) Position diaphragm.
(c) Free up and seat properly.
(a) Bleed brakes.
(b) Lubricate plunger.
(E) Add brake fluid.
SERVICE PROCEDURES
SERVICE BRAKES
Adjusf
ing the Brakes
NOTE:
Normally self adjusting brakes will not re-
quire manual adjustment but in the event of a brake
reline it may be advisable to make the initial adjust-
ment manually to speed up the adjusting time.
(1) Jack
up
the vehicle
so
all wheels are free to turn.
(2) Remove the rear adjusting hole cover from the
backing plate on all of the brake supports of the ve-
hicle.
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