the operation by connecting the brake system to that
(5) Disassemble the air chamber, by loosening the
of a towing vehicle and operating the brakes. Check
nuts (9) alternately and in increments to relieve the
for leaks with a soap bubble solution. Correct any
tension of the spring (16). Disassemble the back plate
(11), diaphragm (12), push rod (13), spring guide (14),
grommet (15), and spring (16) from the front plate
b. Cleaning and Inspection.
(1) Open the drain cock (13, fig. 4-21) at the bot-
(1) Clean the metallic parts of the brake chamber
with dry cleaning solvent (fed. spec. P-D-680). Wash
tom of the lower air reservoir (17) to drain system.
Disconnect the air hoses from the relay valve (para 4-
the diaphragm with a detergent and water solution.
(2) Inspect the diaphragm for cracks,
60a). Tag hoses
to facilitate reassembly.
contact point. Replace a damaged diaphragm.
(27), lock washers (28), and flat washers (29) that
(3) Inspect the covers for cracks, dents, distor-
secure the brake relay valve (30) to the front plate of
the lubricating and servicing unit; remove the relay
tion, and damaged threads; replace a damaged cover.
(4) Inspect the spring for rust, distortion, and for
loss of tension. Replace a damaged spring.
(3) Refer the defective relay valve to direct sup-
port maintenance for repair.
(5) Inspect the master cylinder for obvious
b. Installation. Installation is the reverse of
damage. If necessary, disassemble and repair it per
that hoses are connected correctly. If you connect
c. Reassembly and Installation.
any hoses improperly, the brake system will fail.
(1) Reassembly of the brake chamber and master
cylinder assembly is the reverse of disassembly.
4-64. Brake Master Cylinder
a. Removal and Disassembly.
the nuts (9) on the screws (8) evenly and alternately
(1) Remove the brake master cylinder (para 4-
to prevent the diaphragm from puckering between
the flanges of the plates.
(2) Pour the brake fluid from the master cylin-
(2) Install the assembled brake chamber and
master cylinder assembly on the front plate of the
(3) The master cylinder is spring loaded, and you
lubricating and servicing unit as shown in figure 4-
must take care when removing the retaining ring (1,
21. Make the necessary
air connections. Make the