JLG 600SC_660SJC Service Manual - Manual (Page 113)

SECTION 5 - CAT CHASSIS (S/N 0300128000 TO PRESENT)
3121157 – JLG Lift – 5-21
5.7 TROUBLESHOOTING
In the event a failure occurs while in operation, refer to the following troubleshooting list for the causes of failure and neces-
sary actions.
Troubleshooting for Piston Motor
TROUBLES (TYPE OF FAILURE) POSSIBLE CAUSES CORRECTIVE ACTIONS
Motor does not rotate. The components other than piston motor and reduc-
tion gear do not work properly. Check to see if the inlet of motor is pressurized or not,
and provide necessary corrections.
Sliding components of the motor are excessively
worn and pressurized oil is leaked. Replace excessively worn parts with new ones.
Remove scratches or burrs, clean all parts thor-
oughly, and reassemble them.
Major parts of the motor are damaged. In this case,
the motor produces abnormal noises. Disassemble the motor and replace all damaged
parts with new ones. Clean up all parts and reassem-
ble them.
Motor load is so great that relief valve operates. Check for load condition, and operate motor under
load corresponding to relief set pressure.
Motor speed is low. Insufficient inflow caused by oil pump and pressure
control valve Check to see if there is necessary flow at the inlet of
motor. Provide necessary repairs.
Required rpm is not obtained because of lowered vol-
umetric efficiency of the motor. Disassemble the motor and check all sliding parts for
excessive wear. Repair or replace worn parts as nec-
essary.
Motor rotates at unstable speed. Pressurized oil in large amount leaking from drain port
caused by wear of motor sliding surface results in a
reduction or variations in speed of rotations. Or, motor
speed is affected by wear of bearings. Disassemble the motor for excessive wear. Replace
all worn parts with new ones. Clean up all the parts,
and reassemble them.
Motor load is so great that automatic 2-speed system
operates. Check for load condition, and operate motor under
load corresponding to automatic 2-speed set pres-
sure.
Oil leakage Damaged oil seals or O-rings have caused oil leakage. Replace damaged oil seals and O-rings with new
ones. When inserting oil seals, take sufficient care not
to damage lips. Oil seals and O-rings can be safely
used up to 80° C. If the hydraulic fluid temperature in
the motor rises above 80° C , measures such as set-
ting a cooler in the hydraulic circuit are necessary.
Pressurized motor case caused by (1-2) and (3-1)
damages oil seals, resulting in oil leakage.
* Pressure resistance of oil seals Working: 0.2 MPa
Intermittent maximum: 0.5 MPa Repair the motor in the same procedures as in (1-2)
and (3-1), and replace oil seals with new ones. When
inserting oil seals, pay full attention not to damage
lips.
Clogged drain piping by foreign substances or nar-
row, long piping makes supply pressure high, which
causes damage to oil seals and results in oil leaks.
*Pressure resistance of oil seals Working: 0.2 MPa
Intermittent maximum: 0.5 MPa Clean clogging of drain piping. Review the piping sys-
tem and lessen piping resistance. With above mea-
sures, prevent pressure greater than 0.3 MPa from
being exerted on oil seals, and replace oil seals with
new ones. When inserting oil seals, pay full attention
not to damage lips.
Abnormal noise, and variations in rota-
tion and pressure caused by cavitation
are remarkable. When motor performs pump operation, when closed
loop is used, when boost is low (standard: 0.4 to 0.5
MPa), boost pressure lowers with set pressure of low
pressure relief lowered, causing cavitation. Provide proper boost pressure by reviewing hydraulic
circuit and replacing low pressure relief with new one.
Then, disassemble the motor, and replace abnormally
worn parts and damaged parts. Clean all the parts
before reassembly.