TM 9-2330-271-14&P
(3) Turn the other adjusting screw located at
(2) Clean bleeder valve and attach tube to
bottom rear face of backing plate clockwise to expand
the rear brake lining in contact with brake drum.
bottle or jar partially filled with hydraulic brake fluid.
(4) Back off adjusting screw just enough to
CAUTION
allow drum to rotate freely.
Do not use brake fluid when refilling
(5) Repeat this procedure on other wheels.
master cylinder. Use clean fluid as
Make both adjustments at each wheel as uniform as
required on the lubrication order
possible.
(6) Repeat adjustment on other brakes. The
(3) Fill hydraulic master cylinder with brake fluid
shoe adjusting bolt and spring assemblies lock them in
set position.
(4) Rotate bleeder valve three-quarters of a
(7) Close drain cock on air reservoir, lower tires
turn counterclockwise. Depress towing vehicle brake
to ground and remove jacks.
pedal to expel air, close bleeder valve before releasing
brake pedal.
4-33.
Bleeding Hydraulic Brake System
NOTE
Do not pump master cylinder dry.
a. General. Proper operation of hydraulic portion of
(5) Expelled air will show as bubbles m brake
brake system requires a solid column of fluid (without air
fluid coming out of tube. Continue step (4) above until
bubbles). Bleed the system to expel any air which may
air bubbles cease.
have entered. Need for bleeding is generally indicated
(6) Remove bleeder tube.
by soft brake action. Bleeding can be done manually or
(7) Repeat steps (1) through (5) on remaining
with pressure feed filler. Towing vehicle must be
wheel cylinders, replenishing fluid in master cylinder
connected to semitrailer for manual bleeding operations.
reservoir as necessary.
(8) Close towing vehicle shutoff valves, open
(1) Connect towing vehicle SERVICE and
air reservoir drain cock and disconnect towing vehicle
EMERGENCY brake line couplings to their associated
SERVICE and EMERGENCY brake line couplings from
semitrailer couplings and open shutoff valves on towing
semitrailer couplings.
vehicle air lines.
(9) Install filler plug and vent tube in top of
master cylinder reservoir.
(10) Close air reservoir drain cock.
c. Pressure Feed Filter Bleeding.
(1) Install pressure feed adapter in hydraulic
master cylinder filler plug hole and connect pressure
feed hose to adapter. The air pressure to the master
cylinder reservoir should be 10 psi to 20 psi and reservoir
should contain sufficient fluid to maintain a constant fluid
level during bleeding.
(2) Repeat steps (2), (4), (6) and (9) of
brake pedal is not required.
4-34.
Brake Internal Lever and Connecting Link
NOTE
Some semitrailers do not incorporate
internal lever and connecting link.
a.
(1) Open air reservoir drain cock.
Figure
4-27.
Bleeding
hydraulic
brake
system.
4-41