Grove Published 11-22-2016, Control # 345-12 5-3
RT9130E-2 SERVICE MANUAL HOIST AND COUNTERWEIGHT
Troubleshooting
Table 5-1
Symptom Probable Cause Solution
1. The hoist will not lower the load or
not lower the load smoothly
a. The problem could be a
plugged or loose pilot orifice.
The pilot orifice is a small pipe
plug with a hole drilled
through it located behind the
pilot port fitting on the brake
valve. If it becomes plugged, it
will prevent the pilot pressure,
from the manifold, from
opening the brake valve. If it
becomes loose, it will allow an
unregulated amount of oil in to
operate the brake valve which
causes erratic brake valve
operation.
a. Remove the pilot hose and
fitting from the brake valve,
then use a 5/32 inch Allen
wrench to remove the pilot
orifice. The diameter of the
orifice is approximately 0.020
in (0.5 mm). Clean and install
the pilot orifice tightly in the
brake valve.
b. The friction brake may not be
releasing as a result of a
defective brake cylinder seal.
NOTE: If the brake cylinder seal is
defective, oil could be leaking
from the hoist vent plug.
b. Check the brake cylinder seal
as follows:
• Disconnect the swivel tee
from the brake release.
Connect a hand pump with
accurate 0 - 2000 psi gauge
and shut-off valve to the -4
J.I.C. fitting in the brake
release port.
• Apply 1000 psi to the brake.
Close shut-off valve and let
stand for five (5) minutes.
• If there is any loss of pressure
in five (5) minutes, the brake
cylinder should be
disassembled for inspection
of the sealing surfaces and
replacement of the seals.
c. Friction brake will not release
as a result of damaged brake
discs.
c. Disassemble brake to inspect
brake discs. Check stack
height by placing the pressure
plate on top of brake spacer.
Press pressure plate down
firmly by hand and measure
gap between motor adapter
and pressure plate. Average
gap must measure between
0.160 in (4 mm) maximum
and 0.080 in (2.0 mm)
minimum. Adjust with discs as
required.
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