STRUCTURAL CD3340B/YB4411
11-52
Published 04/07/2015 Control # 569-00
Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY
A -The hoist will not lower the load or
not lower the load smoothly.
1.The friction brake may not be
releasing as a result of a defective
brake cylinder seal.
1.Check brake cylinder seal as follows:
NOTE: If the brake cylinder seal is
defective, leaking will occur from the
hoist vent plug.
A. Disconnect the swivel tee from the
brake release port. Connect a hand
pump with an accurate 0-13 790 kPa
(0-2000 psi) pressure gauge and
shut-off valve to fitting in the brake
release port.
B.Apply 6895 kPa (1000 psi) to the
brake. Close the shutoff valve and let
stand for five (5) minutes.
C. If there is any loss of pressure in five
(5) minutes, the brake cylinder should
be disassembled for inspection of
sealing surfaces and replacement of
the seals. Refer to “Motor Support/
Brake Cylinder Service” on
page 11-45
2. Friction brake will not release as a
result of damaged brake disc.
2. Disassemble the brake to inspect
brake discs. Check stack-up height
as described in “Motor Support/Brake
Cylinder Service”, page 11-45.
B - Oil leaks from vent plug. 1. Same as A2. 1. Same as A2.
2. Motor seal may be defective as a
result of high system back pressure.
2. System back pressure must not
exceed 3448 kPa (500 psi). Inspect
hydraulic system for a restriction in
the return line from the main control
valve to the hydraulic tank.
Oil analysis may indicate
contamination has worn the motor
shaft and seal. Install a new motor
seal.
C - The brake will not hold a load with
the control lever in neutral.
1. Excessive system back pressure
acting on the brake release port.
1. Same as Remedy 2 of possible
cause B2.
2. Friction brake will not hold due to
worn or damaged brake discs.
2. Same as Remedy 3 of Possible
Cause A2.
3. Brake clutch is slipping. 3. Improper planetary gear oil may
cause the brake clutch to slip. Drain
old gear oil and flush hoist with a
suitable solvent. Thoroughly drain the
solvent and refill hoist with
recommended planetary oil. See
Section 5.
D - The hoist runs hot.
1. Excessively worn or damaged
internal hoist parts.
1. Disassemble hoist to inspect/ replace
worn parts.
Reference Only
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