JLG 660SJ Service Manual - Manual (Page 64)

SECTION 3 - CHASSIS & TURNTABLE
3-20 – JLG Lift – 3121298
Troubleshooting
Table 3-3. Excessive Noise and/or Vibration
Item Description Action
Check oil level in reservoir and oil
supply to motor. Insufficient hydraulic fluid could lead to cavitation that would cause sys-
tem noise. Fill reservoir to proper level. Ensure oil supply to motor is adequate and
lines are unobstructed.
Check for air in system. Air trapped in system lines or motor could result in cavitation that would
cause system noise. Ensure all system lines and components are purged of air.
Inspect output shaft couplings. A loose or incorrect shaft coupling will produce vibrations that could result
in system noise. Ensure correct coupling is used and that it fits properly on shaft.
Inspect output shaft alignment. Misaligned shafts create excessive frictional vibration that could result in
system noise. Ensure shafts are properly aligned.
Hydraulic oil viscosity above limits. Viscosity above acceptable limits will result in cavitation that would lead
to system noise.
Replace hydraulic oil with appropriate fluid for operating conditions.
Table 3-4. System Operating Hot
Item Description Action
Check oil level in reservoir and oil
supply to pump. Insufficient amount of hydraulic fluid will not meet system cooling
demands. Fill reservoir to proper level.
Inspect heat exchanger, (if
equipped). If heat exchanger fails, or becomes obstructed, it may not meet system
cooling demands. Ensure heat exchanger is receiving adequate air flow and is in good operat-
ing condition. Repair or replace as necessary.
Check system relief valves. If a system relief valve becomes unseated for an extended period of time or
fails for any other reason, system could become overheated. Repair or replace any malfunctioning relief valves as applicable and verify
loads on machine are not excessive.
Table 3-5. Won’t Shift or Slow to Start
Item Description Action
Check signal line to servo control
port. Obstructed or restricted flow through servo control signal lines could
result in slow shift or no shift motor conditions. Ensure signal lines are not obstructed or restricted and signal pressure is
adequate to shift motor.
Check correct supply and drain ori-
fices are properly installed and not
obstructed. Supply and drain orifices determine motor shift. The smaller the orifice,
the longer the time it takes to shift the motor. Obstruction also increases
shift times. Ensure proper control orifices are installed in motor and not obstructed.
Clean or replace as necessary.