JLG 120HX ANSI Service Manual - Manual (Page 99)

SECTION 3 - TROUBLESHOOTING
3120686 – JLG Lift – 3-17
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Table 3-5.Hydraulic System - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY
HYDRAULIC SYSTEMS - GENERAL.
Hydraulic pump noisy.
Air entering system through broken line or fitting.
(Suction Side.) Repair or replace line or fitting.
Suction screen dirty. Clean suction screen.
Air bubbles in oil. (Reservoir oil too low. Replenish oil as required.
Suction hose squeezed shut. Determine cause and repair.
Oil filter dirty. Replace hydraulic filter.
Wrong type of hydraulic oil. Replace hydraulic oil.
Pump cavitating. (Vacuum in pump due to oil
starvation.)
Restricted suction line. Clean, repair, or replace line.
Restricted reservoir air vent. Clean or replace vent.
Oil viscosity too high. Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Air leak in suction side of tank. Repair leak.
Restricted suction strainer. Clean strainer.
System overheating.
Oil viscosity too high. Drain system and replace with recommended oil.
(Refer to Hydraulic Oils.)
Bypass valve not operating properly. Repair or replace valve.
Main relief valve set too low. Reset valve as required.
Hydraulic system oil low. Replenish oil as necessary.
Port relief set too high. Reset valve as required.
Restricted or blocked return line. Repair or replace line.