manufacturers recommend pulling two wheels-one on
each side. Look for loose or broken brake shoe retracting
springs, worn clevis and cotter pins in the brake
operating mechanisms, and grease or oil leaks at the
wheel bearing grease retainer. Check for any signs of
brake fluid leakage around the wheel cylinders or caliper
Brake linings that pass inspection for wear must be
securely fastened to the brake shins and free from grease
and oil. Small grease or oil spots can be removed from
the lining with a nonoil base solvent. Linings saturated
with grease or oil should be replaced only after the
source of contamination has been repaired.
Badly worn or scored brake drums/rotors (fig. 6-2)
should be machined smooth and true on a lathe or
replaced. Cracked brake drums (fig. 6-3), or brake
drums that have been machined beyond their maximum
allowable diameter should be discarded. Brake drums
and discs have the maximum or discard diameters cast
into their outer surfaces (fig. 6-4).
Brake shoe and drum trouble not immediately
evident when the wheels are pulled, yet that is detected
during road tests, may be caused by the wrong kind of
lining, ill-fitting brake shoes, or brake drums slightly out
of round. The clue to these troubles may be chattering,
spongy, or grabbing brakes.
PEDAL GOES TO THE FLOOR (LOW
Pedal reserve (fig. 6-5) is the distance from the
brake pedal to the floorboard with the brakes applied.
Low or no pedal reserve indicates brake problems.
When there is no pedal reserve or an unlikely occurrence
with a dual master cylinder, it could mean anything from
a lack of brake fluid, to worn brake linings, a faulty
master cylinder, or only a simple brake adjustment. Each
of these conditions demands that you closely inspect the
Dragging brakes are caused by the following: one
or more sets of shoes being adjusted too tightly, broken
or weak return springs, a wheel cylinder piston that is
stuck, drums that are out of round, defective lining
material, loose anchor pins, or clogged lines or hoses.
When both rear wheels drag, the cause may be the
parking cable linkage being adjusted too tightly or a
frozen parking brake cable. All wheels dragging can be
the result of a stuck master cylinder pedal linkage or a
defective power booster.
Before troubleshooting brake systems by
road testing, be sure that the vehicle is
mechanically sound. Different size tires, low
tire pressures, faulty shock absorbers, loose
wheel bearings, and worn front-end parts may
each indicate brake problems where there are
Navy vehicles seldom have the wrong kind of brake
lining. However, an inexperienced mechanic may
reverse the primary and secondary shoe on one of the
wheels or interchange them between wheels so that the
shoes are not exactly mated with the drums against
which they expand. If you replace shoes or machine the
drum/rotor on one side, do the same to the opposite side
to prevent pull or loss of control.
The preceding paragraphs apply to most braking
systems but do not list all of the problems you will have.
For other probable causes of trouble and their remedies
in standard hydraulic brake systems, refer to table 6-1.
Figure 6-5.-Example of pedal reserve.