DEMO - 1965 Ford Truck Shop Manual - ForelPublishing.com

2-2 GROUP 2 - BRAKES
DIAGNOSIS GUIDE—STANDARD HYDRAULIC BRAKES
BRAKES DO NOT APPLY
shoes are serviced. A defective check
valve can cause a loss of residual
pressure in the system causing air to
enter at the wheel cylinder piston,
Bleed the system to remove air from
the lines, and adjust the brakes. Refill
the master cylinder reservoir with
heavy-duty brake fluid. If the brakes
do not apply after making these
checks and adjustments, fluid may be
leaking past the piston cups in
the master cylinder or brake wheel
cylinder(s). If the trouble is in the
master cylinder or brake wheel cylin-
der(s), remove and repair.
If the brake pedal travels all the
way down to the floor without noticeable
brake action, check the brake
fluid level in the master cylinder reservoir.
Refill the reservoir if necessary.
Check the entire hydraulic system
for fluid leaks, and make the
necessary adjustments.
If the brake pedal feels spongy
when pushed down, air has entered
the hydraulic lines. Air can enter the
lines if the fluid level in the master
cylinder reservoir is too low, or if the
brake wheel cylinder pistons are not
held firmly in place when the brake
EXCESSIVE PEDAL TRAVEL
Check for air in the brake lines
and bleed the system if necessary. Ad-
just or reline the brakes as needed,
UNEVEN NOISY,
GRABBING, OR HARD
OPERATING BRAKES
shoe adjustment; warped or mis-
aligned shoes; webs glazed or greasy
linings; and incorrectly ground or
wrong linings, are a few of the causes
for uneven, noisy, pulling, grabbing,
or hard brakes. Adjust or replace the
parts as needed to eliminate the
trouble. Lining glaze can be removed
by rubbing the lining with mediumgrade
sandpaper until the lining has
a dull finish.Always adjust the brakes
after correcting any of these brake
troubles.
Remove the brake drums so that a
complete inspection of the brake assemblies
can be made to determine
the cause of the trouble.
Excessive dust and dirt in the
brake lining rivet holes or in the
brake drum can cause brake squeal.
Remove the dirt with a scraper and
an air hose.
Drums which are out-of-round or
loose at the hub; frozen master cylinder
or brake cylinder piston(s); defective
check valve; improper brake
BRAKES DO NOT
RELEASE
Check for an improperly adjusted draulic system with clean denatured
brake pedal, a restricted by-pass port alcohol before adding new brake
in the master cylinder, or swollen fluid.
master cylinder piston cups. Check If the trouble is in the master cylfor
a defective check valve restricting inder, remove and rebuild the cylfluid
passing through the system. inder.
Check for sticking brake cylinder If the truck must be moved when
pistons caused by dirty or contami- the brakes are locked, open a brake
nated brake fluid. cylinder bleeder screw for a moment
Adjust the brake pedal if necessary. to let out a few drops of brake fluid.
If the adjustment does not correct the This operation will release the brakes
trouble, check the condition of the but will not eliminate the cause of
brake fluid. Replace dirty or contam- the trouble.
inated fluid. Clean the entire hy-
PRELIMINARY TESTS—POWER
BRAKES
With the engine stopped, eliminate
all vacuum from the system by
pumping the brake pedal several
times. Then push the pedal down as
far as it will go, and note the effort
required to hold it in this position. If
the pedal gradually moves downward
under this pressure, the hydraulic
system is leaking and should
be checked by a hydraulic pressure
test.
With the brake pedal still pushed
down, start the engine. If the vacuum
system is operating properly,
the pedal will move downward. If
the pedal position does not change,
the vacuum system is not operating
properly and should be checked by
a vacuum test.
VACUUM TESTS
CHECK VALVE TEST
Disconnect the line from the bottom
of the vacuum check valve, and
connect a vacuum gauge to the