t h e i r r e s p e c t i v e s e a t s a n d m e a s u r e with
3-52. Brake Valve
micrometer. Record this measurement.
a . General. The brake valve is located under the
( 7 ) Remove spool and place the steel balls in
brake pedal and inching pedal floor board panel.
their respective seats and measure. Subtract the
The valve is essentially two valves in one. The
s m a l l e r dimension. If difference is less than 0.004
closed center ball type valve operates the brake
i n c h , replace the spool.
w i t h the power being furnished by the accumulator.
(8) Inspect the nylon pins in the charging
A pilot valve and charging valve control the flow
valve plug and the pilot valve adjusting plug for
f r o m the pump to charge the accumulator within its
w e a r or damage. These pins are used to keep the
o p e r a t i n g range. The number of brake applications
plugs from working loose.
after the engine is stopped is limited only to the size
of the accumulator.
Always use new seals when overhauling the brake
(1) Remove the ladder and access panel on the
driven side (TM 10-3930-243-12).
( 1 ) Install the filter (52, fig. 3-112) into the
(2) Refer to figure 3-111 and remove the brake
valve body (3).
(2) Install the steel washer (51).
112 and disassemble the brake valve assembly in
(3) Install O-ring (25).
numerical sequence as follows:
(4) Install the check valve seat (50), check
valve (49), spring (48), and screw plug (46) on
w h i c h a new O-ring (47) has been placed into the
Measure the depth that the adjusting plug (32) is
valve body (3).
below the surface of valve body (3). Scribe a mark in
line with plug slot. Record this information, as it
(5) Torque the screw plug (46) to 35 to 40 ft.
must be used in reassembly of valve.
(6) Install the locknut (45) and torque to 35 to
(1) The piston (6) pulls out of the valve body
40 ft. lbs.
(2) Shims (7 and 8) will be found inside
( 7 ) Install the ball valve and seat (22) in the
p i s t o n . The shims are used for adjusting the brake
valve body with the flange up. Be sure that the seat
line pressure and must be used in the reassembly of
is properly placed in the valve body. Use a wooden
valve. Never mix parts from another valve.
dowel to push this assembly into place.
(3) Remove O-ring (10) from valve body.
(8) Place the spring (20) on the ball guide (21)
and then the washer (19). seal (18) (with lip
(4) Remove snap ring (11) and washer (12).
t o w a r d the steel washer) and the teflon backup ring
(5) Remove plunger (13) from valve.
( 6 ) Remove plug (15) from valve and remove
spring (20) and guide (21).
( 9 ) Place a new O-ring (16) on the plug (14)
a n d place the assembled parts inside the plug and
( 7 ) Use a wooden dowel or other soft material
to push out ball valve and seat (22).
assemble to the body.
(10) Tighten the plug (15) to 35 to 40 ft. lbs.
( 8 ) Remove plug (24) and remove pilot valve
spring (26), ball (27), spool (28) and seat (29).
(11) Place a new O-ring (30) on the pilot valve
seat (29) and install in the valve body (3).
( 9 ) Remove pilot valve plug (32) and remove
spring (34), seat (35) and ball (36).
(12) Push the pilot valve seat into place with a
(10) Remove plug (38) and remove spring
(40), stop (41), and charging valve spool (42).
(13) Install the pilot valve spool (28), the long
end of the spool in the "up" position.
( 1 1 ) Loosen locknut (45). Remove screw (46)
a n d remove spring (48), poppet (49), seat (50) and
( 1 4 ) Place the steel ball (¼ inch diameter) on
its seat in the pilot valve insert.
c. Cleaning and Inspection.
(15) Install a new O-ring (25) on the plug
(15). Place a small amount of grease on the end of
(1) Clean all parts.
the spring (26) and insert it into the plug. The
( 2 ) Inspect the piston (6, fig. 3-112) for nicks
grease is to hold the spring in the plug during
(3) Inspect surface of the valve seat in the
(16) Tighten the plug (15) to 30 to 35 ft. lbs.
plunger (13) for proper seating and outside signs of
(17) Install the spring (34), ball seat (35), and
steel ball (36) (¼ in. diameter) using grease to hold
(4) Inspect the seat in the bronze plunger.
(5) Inspect valve seat in end of pilot valve
(6) Assemble pilot valve spool (28) inside pilot
v a l v e insert (29) and place the steel balls (27) in