Brake Applicator Valve and Differential Pressure Switch

TM 10-3930-242-34

(8) Remove plug (24) and remove pilot valve

5-11. Automatic Slack Adjusters

spring (26), ball (27), spool (28) and seat (29).

a. Removal. Remove the automatic slack ad-

(9) Remove pilot valve plug (32) and remove

j u s t e r s (TM 10-3930-242-12).

spring (34), seat (35) and ball (36).

b. Disassembly. Refer to figure 5-8 and disas-

(10) Remove plug (38) and remove spring

s e m b l e the automatic slack adjuster in numeri-

(40), stop (41), and charging valve spool (42).

cal sequence.

(11) Loosen locknut (45). Remove screw (46)

c. Cleaning and Inspection.

and remove spring (48), poppet (49), seat (50) and

filter (52).

(1) Clean the automatic slack adjuster,

using solvent P-D-680, or equal. Do not saturate

c. Cleaning and Inspection.

t h e diaphragm with solvent.

(1) Clean all parts thoroughly, using sol-

(2) Inspect the automatic slack adjuster

v e n t P-D-680, or equal.

h o u s i n g for cracks and breaks.

(2) Inspect the piston (6, fig. 5-10) for nicks

( 3 ) Inspect the diaphragm for damage.

a n d scratches.

( 4 ) Inspect hardware for damage.

(3) Inspect surface of the valve seat in the

d. Reassembly. Refer to figure 5-8 and reas-

plunger (13) for proper seating and outside signs

s e m b l e the automatic slack adjuster.

of wear.

e. Installation. Install the automatic slack ad-

( 4 ) Inspect the seat in the bronze plunger.

juster and bleed the hydraulic brake system

( 5 ) Inspect valve seat in end of pilot valve

(TM 10-3930-242-12).

insert (29).

( 6 ) Assemble pilot valve spool (28) inside

5-12. Brake Applicator Valve and Differen-

p i l o t valve insert (29) and place the steel balls

tial Pressure Switch

(27) in their respective seats and measure with a

a. Removal.

m i c r o m e t e r . Record this measurement,

(1) Remove the driver's floor plate and ac-

(7) Remove spool and place the steel balls in

cess panel under the left fender (TM

their respective seats and measure. Subtract

10-3930-242-12).

t h e smaller dimension. If difference is less than

(2) Refer to figure 5-9 and remove the diffe-

0.004 inch, replace the spool.

rential pressure switch and brake applicator

( 8 ) Inspect the nylon pins in the charging

valve.

valve plug and the pilot valve adjusting plug for

wear or damage. These pins are used to keep the

NOTE

p l u g s from working loose.

R e p l a c e a defective differential pressure switch

with a new switch.

d. Reassemble.

b. Disassembly of Brake Valve. Refer to figure

5 - 1 0 and disassemble the brake valve assembly

NOTE

i n numerical sequence as follows:

Always use new seals when overhauling the brake

valve.

NOTE

Measure the depth that the adjusting plug (32) is

( 1 ) Install the filter (52, fig. 5-10) into the

below the surface of valve body (3). Scribe a mark in

valve body (3).

line with plug slot. Record this information, as it

must be used in reassembly of valve.

( 2 ) Install the steel washer (51).

(3) Install O-ring (25).

(1) The piston (6) pulls out of the valve body

(3) Install O-ring (25).

(3).

( 4 ) Install the check valve seat (50), check

(2) Shims (7 and 8) will be found inside pis-

v a l v e (49), spring (48), and screw plug (46) on

ton. The shims are used for adjusting the brake

which a new 0-ring (47) has been placed into the

l i n e pressure and must be used in the reassem-

valve body (3).

bly of valve. Never mix parts from another

(5) Torque the screw plug (46) to 35-40 ft-

valve.

lbs.

(3) Remove O-ring (10) from valve body.

( 6 ) Install the locknut (45) and torque to

(4) Remove snapring (11) and washer (12).

35-40 ft-lbs.

(5) Remove plunger (13) from valve.

(7) Install the ball valve and seat (22) in the

(6) Remove plug (15) from valve and remove

v a l v e body with the flange up. Be sure that the

spring (20) and guide (21).

seat is properly placed in the valve body. Use a

(7) Use a wooden dowel or other soft mater-

w o o d e n dowel to push this assembly into place.

ia1 to push out ball valve and seat (22).

5-21