JLG 450A Service And Maintenance Manual page 99

.
TROUBLE
Hydraulic pump noisy.
Pump cavitating. (Vacuum in pump due to oil
starvation.)
System overheating.
3120869
Table 3-5.Hydraulic System - Troubleshooting
PROBABLE CAUSE
HYDRAULIC SYSTEMS - GENERAL.
Air entering system through broken line or fitting.
(Suction Side.)
Suction screen dirty.
Air bubbles in oil. (Reservoir oil too low.
Suction hose squeezed shut.
Oil filter dirty.
Wrong type of hydraulic oil.
Restricted suction line.
Restricted reservoir air vent.
Oil viscosity too high.
Air leak in suction side of tank.
Restricted suction strainer.
Oil viscosity too high.
Bypass valve not operating properly.
Main relief valve set too low.
Hydraulic system oil low.
Port relief set too high.
Restricted or blocked return line.
– JLG Lift –
SECTION 3 - TROUBLESHOOTING
REMEDY
Repair or replace line or fitting.
Clean suction screen.
Replenish oil as required.
Determine cause and repair.
Replace hydraulic filter.
Replace hydraulic oil.
Clean, repair, or replace line.
Clean or replace vent.
Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Repair leak.
Clean strainer.
Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Repair or replace valve.
Reset valve as required.
Replenish oil as necessary.
Reset valve as required.
Repair or replace line.
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