JLG 150HAX ANSI Service Manual - Manual (Page 144)

SECTION 6 - SCHEMATICS
6-16 – JLG Lift – 3120679
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Table 6-5.Hydraulic System - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY
HYDRAULIC SYSTEM - GENERAL
Hydraulic pump noisy.
Air entering system through broken line or fitting.
(Suction Side.) Repair or replace line or fitting.
Air bubbles in oil. (Reservoir oil too low.) Replenish oil as required.
Oil filter(s) dirty. Clean and/or replace filter(s) as necessary.
Pump cavitating. (Vacuum in pump due to oil starvation.)
Restricted suction line. Clean, repair, or replace line.
Restricted reservoir air vent. Clean vent.
Oil viscosity too high. Drain system and replace with
recommended oil. (Refer to Hydraulic Oils.)
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 high. Reset valve as required.
Hydraulic system oil low. Replenish oil as necessary.
Pump not delivering oil.
Restricted suction line. Clean, repair, or replace line.
Air entering system through broken line or fitting. Repair or replace line or fitting.
Broken pump drive shaft/pump
coupling. Repair or replace pump/pump
coupling.
Function sluggish during operation. (System pressure too low.)
Main relief valve set too low. Reset valve as required.
Pump section not delivering sufficient oil. Repair or replace pump section or pump.
Main relief valve stuck in open position. Clean, repair, or replace valve.
(Check system oil for contamination.)
Oil viscosity too low. Drain system and replace with
recommended oil. (Refer to Hydraulic Oils.)
Leak in component, line or fitting. Repair or replace component, line or
fitting.
Scored valve spool; scored cylinder. Replace valve; replace cylinder.