Paccar Braden PD12C - Clean and Inspect; Assembly

52
BRAKE VALVE SERVICE
4. Remove spool plug and carefully remove spool
assembly.
5. Remove the damper piston from the spool. The piston
will come out slowly, because of a partial vacuum
formed as it is removed. Use extreme care to avoid
damaging the polished surfaces of the piston or spool.
6. Remove the check valve spring retainer, spring and
check valve poppet. Check spring free length. Replace
spring if less than 1-1/2 in. (38.1 mm) long.
CLEAN AND INSPECT
1. Discard all O-rings and backup rings. Clean all parts
in solvent and blow dry. Inspect polished surfaces of
spool and damper piston for damage which may cause
binding or leakage. Inspect spool bore in valve housing
for damage or scoring. Inspect check valve seat in
valve housing and check valve poppet. If the spools,
bores or valves are damaged, the entire valve must be
replaced as these parts are not serviced separately.
2. Inspect the .020 inch (.5 mm) orice in the end of the
spool and the pilot orice to be certain they are open.
ASSEMBLY
1. Install new O-rings on the plug and spring retainers.
2. Install new O-rings and backup rings on the spool and
damper piston as shown. Ensure each backup ring is
on the correct side of its O-ring. Take care not to cut
the O-rings during assembly. Let the spool and damper
piston set for ten minutes before installing them in their
respective bores. This will allow the O-rings to return to
their original size after being stretched.
3. Lubricate the spool and damper piston O-rings with
hydraulic oil. Carefully install the damper piston into
the spool.
4. Lubricate the spool bore and spool O-rings with
hydraulic oil. Carefully install the spool into the valve
housing. Always install the spool from the plug end
as shown to minimize the possibility of damaging the
O-ring. Install the plug, spool spring and spring retainer.
5. Install the check valve poppet, spring and check valve
spring retainer.
6. Install the motor drain check ball, spring and elbow
tting.
7. Install the pilot orice into the valve housing.
8. The brake valve is complete and ready to be installed
on hoist motor.