is controlled by shims assembled beneath the
(18) Install the pilot valve adjusting plug (32)
operating piston. Add shims to increase pressure,
on which a new O-ring (33) has been installed.
r e m o v e shims to decrease pressure. Use a 0-2,000
pound per square inch (psi) gage to test valve.
dimension. which was recorded at the time of
(a) Screw gage into brake port on valve.
d i s a s s e m b l y . and line up the slot in the plug with
(b) Fill pump with hydraulic oil, and attach
the mark on the face of the valve body (3). If new
it to accumulator port on valve.
parts have been used to service the valve at this
(c) P u m p u p v a l v e t o 1 , 9 0 0 p s i .
point. there is a possibility that the accumulator
(d) Remove boot (5) and depress operating
c h a r g i n g limits have charged. This is checked when
piston (6) all the way in and read gage. The correct
the brake valve is installed on the vehicle. One full
brake line pressure should read 225 to 275 psi.
turn of the adjusting plug changes the high limit by
(2) Accumulator pressure is the pressure of the
2 0 0 psi. The high limit is raised by screwing the
oil in the accumulator used for applying the brakes.
plug into the body and lowered by screwing the
The maximum accumulator or high limit pressure
p l u g out of the body.
is controlled by the pilot valve spring. This is
( 2 0 ) Install a new quad ring seal (42) on the
purposely set below the steering relief valve for
c h a r g i n g valve spool (43) and install the spool in
safety reasons, otherwise the components beyond
the body. Use extra care in installing this spool so as
the brake would not operate. After the brakes
n o t to damage the lands on either the spool or the
h a v e been applied a number of times, the pressure
b o d y . Be sure that the spool is pushed all the way
decreases to a low limit, at which time the ac-
into the body so that the end of the spool contracts
c u m u l a t o r recharges. The pressure is the low limit
t h e plug in the end of the valve. At no time is it
that valve starts to recharge the accumulator. The
n e c e s s a r y to force this spool.
h i g h limit is the adjustable pressure, and once this
(21) Install the charging valve spring (40).
is set, it automatically, by brake valve design,
(22) Install the stop (41) inside the spring.
d e t e r m i n e s the low limit or cut in pressure to start
( 2 3 ) Install a new O-ring (39) on the charging
the recharge cycle. The high limit is adjusted by
v a l v e plug (38) and insert it into the valve body.
turning the pilot valve adjusting plug (32). One full
Install retainer ring (37).
t u r n of the plug changes the limit by 200 psi, ½
( 2 4 ) Install a new "V" block seal (14) on the
turn by 100 psi and ¼ by 50 psi. The high limit is
p l u n g e r ( 1 3 ) with the edge of the seal toward the
raised by screwing the plug into the body and
valve seat (22). Install the plunger.
lowered by screwing the plug out of the body.
(25) Install the washer (12).
(a) Fill pump with hydraulic oil and attach
(26) Install the snap ring (11) and engage it in
it to accumulator port on valve.
the groove about the washer.
( b ) Pump up valve until a decisive click is
(27) Install the O-ring (10).
h e a r d , caused by shifting of pilot valve, and note
(28) Install the shims (7 and 8) and spring (9)
g a g e reading. The reading should be 1,300 psi, if
i n the piston (6) and push it into the valve body.
not adjust the pilot valve plug (32).
(29) Make sure the piston is operating freely,
(c) After adjusting high limit pressure let the
and then slowly release it. Check the clearance
pressure leak down until another click is heard
under the flange of the piston. If new parts have
w h e n the low pressure reaches between 650 to 550
been used, it may be necessary to either add or
s u b t r a c t shims (7 and 8) from inside the piston (6)
( 3 ) While pressure testing valve, check for
i n order to get the proper clearance at this point.
leakage. Leakage from either the brake port or
Proper clearance is from 0.199 to 0.211 inch.
return port should be less than 60 drops per
(30) Install the boot (5) and ring (4).
m i n u t e . No leakage is permissible from the pressure
e. Test Procedure.
port (38). It is not necessary to exceed 1,900 psi for
( 1 ) Before the brake valve is installed in the
testing pressure as system pressure is always less.
forklift, gage test it on work bench to insure that it
is properly assembled. Brake pressure is the
( 1 ) Refer to figure 3-111 and install the brake
regulated accumulator pressure allowed to pass
through the valve to apply brakes. It is at
(2) Install the access panel and the ladder
maximum when the brake valve piston is com-
assembly (TM 10-3930-243-12).
pletely depressed. Maximum pressure at the valve