JLG 40H Service Manual - Manual (Page 126)

SECTION 3 - TROUBLESHOOTING
3-14
– JLG Lift – 3120240
Table 3-5. Hydraulic Assembly Troubleshooting.
TROUBLE PROBABLE CAUSE REMEDY
HYDRAULIC SYSTEM - GENERAL.
Hydraulic pump noisy. Air entering system through broken line or fitting.
(Suction side.)
Air bubbles in oil. (Reservoir oil level too low.)
Suction filter dirty.
Oil filter dirty.
Restricted suction line.
Repair or replace line or fitting.
Replenish oil as necessary.
Clean or replace filter.
Replace hydraulic filter.
Clean, repair or replace line.
Pump cavitation. (Vacuum in pump due to oil
starvation.) Restricted suction line.
Restricted reservoir air vent.
Oil viscosity too high.
Air leak on suction side of tank.
Suction filter dirty.
Clean, repair or replace line.
Clean or replace air vent.
Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Repair leak.
Clean or replace filter.
System overheating. Oil viscosity too high.
Bypass valve not operating properly.
Main relief valve set too high. (Racine)
Main relief valve set too low. (Vickers)
Hydraulic system oil low.
Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Repair or replace valve.
Reset valve as required.
Reset valve as required.
Replenish oil as necessary.
Pump not delivering oil. Restricted suction line.
Air entering system through broken line or fitting.
Broken pump drive shaft/pump coupling.
Splines worn in drive disc.
Clean, repair or replace line.
Repair or replace line or fitting.
Repair or replace pump/pump coupling.
Replace drive disc.