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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 that may cause
binding or leakage. Inspect spool bore in valve hous-
ing 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 brake valve
must be replaced. Check the free length of main pis-
ton spring. Replace if less than 3-7/16 inch (87.3 mm)
long. Check the free length of the check valve spring.
Replace if less than 1-1/2 inch (38.1 mm) long.
2. Inspect the 0.020–inch (0.5 mm) orifice in the end of
the spool to be certain it is open.
O-RING
BACK-UP RING
ASSEMBLY
1. Install new O-rings and backup rings on spool and
damper pistons as shown. It is important that 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 piston set for 10 minutes before installing
them into the brake valve housing. This allows O-rings
to return to their original size after being stretched.
2. Install new O-rings on the plug and spool retainers.
3. Lubricate the spool and damper piston O-rings with
hydraulic oil. Carefully install the damper piston into
the spool. Carefully install the spool into the valve
housing. Always install the spool into the valve body
from the plug end, so the O-ring enters the bore first.
Install the spring seat, spool spring, damper piston ex-
tension and spring retainer.
4. Install the check valve poppet, spring and check valve
retainer.
5. Install the motor drain check ball, spring and fitting.
6. The brake valve is now completely assembled and
ready to be installed on the hoist motor.
2. Remove the spool spring retainer and spool spring.
Remove the spool plug and carefully remove the
spool assembly. Remove the damper piston from the
spool. The piston will come out of the spool slowly,
because of a partial vacuum formed between the two.
Use extreme care to avoid damaging the polished
surfaces of either piece
3. Remove the check valve spring retainer, spring and
check valve poppet.
