Brake Cylinder Service - Paccar BRADEN HP125B Installation Maintenance And Service Manual

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DISASSEMBLY
CAUTION
The motor adapter is under spring tension from the
brake springs. Loosen each of the capscrews one turn
at a time until spring tension is released.
1. Set the brake assembly on a work bench with the motor
adapter up. Remove the eight capscrews (item 32) and
lockwashers (item 31). Use a crisscross pattern and
loosen each capscrew one turn at a time until spring
tension is released.
2. Remove the motor adapter (item 40). Lift out all the
brake discs (item 26), friction discs (item 25), and the
spacer (item 53).
3. Remove and discard the O-Ring and backup ring (items
28 & 27) from the motor adapter. Remove and discard
the brake piston seal (item 30) from the brake cylinder.
Remove the steel piston backup ring (item 59).
4. Remove the pressure plate (item 52) and the springs
and spring spacer (items 62 & 55) from the brake cylin-
der.

BRAKE CYLINDER SERVICE

55 52 59
53
30
31
32
28
27
40
5 62 26 25
CLEAN AND INSPECT
1. Thoroughly clean and inspect all parts at this time.
Check sealing surfaces on both the motor adapter and
brake cylinder. Be sure the brake release port is open
and free of contamination.
2. Place friction brake disc on fl at surface and check for
distortion with a straight edge. Friction material should
appear even across entire surface with groove pattern
visible. Replace friction disc if splines are worn to a
point, disc is distorted, friction material is burned or
worn unevenly, or groove depth is less than 0.003 in.
(0.08 mm).
3. Place steel disc on fl at surface and check for distortion
with a straight edge. Check surface for signs of ma-
terial transfer or excessive heat. Replace steel disc if
distorted, heat discolored, or mechanically damaged.
CAUTION
Failure to replace brake springs as a set may result in
uneven brake application pressure and repeated brake
spring failure.
4. Check brake spring free length. Minimum free length is
1.5 in. (38.1 mm). Check springs for any signs of crack-
ing or failure. If a brake spring must be replaced for any
reason, then ALL brake springs must be replaced.
35

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