JLG 18RS Service Manual - Manual (Page 124)

SECTION 5 - HYDRAULICS
5-34 – JLG Lift – 3121284
Table 5-5. System Noise or Vibration
Item Description Action
Reservoir oil level Low oil level leads to cavitation. Fill reservoir.
Aeration of the oil/pump inlet vacuum Air in system decreases efficiency of units and controls.
Air in system is indicated by excessive noise in pump,
foaming in oil, and hot oil. Find location where air is entering into the system and repair. Check that inlet
line is not restricted and is proper size.
Cold oil If oil is cold, it may be too viscous for proper function and
pump cavitates Allow the oil to warm up to its normal operating temperature with engine at
idle speed.
Pump inlet vacuum High inlet vacuum causes noise/cavitation. Check that inlet line is not restricted and is proper size. Check filter and bypass
switch.
Shaft couplings A loose shaft coupling causes excessive noise. Replace loose shaft coupling.
Shaft alignment Misaligned pump and prime mover shafts create noise. Align shafts.
Charge/system relief valves Unusual noise may indicate sticking valves. Possible con-
tamination. Clean/replace valves and test pump.
Table 5-6. Neutral Difficult or Impossible to Find
Item Description Action
Input to pump control Input to control module is operating improperly. Disconnect input and check to see if pump comes back to neutral. If Yes, input
fault, replace/repair external controller. If No, go to next step.
Pump control neutral Neutral set improperly. Shunt servo gauge ports M4 and M5 together with external hose and see if
pump comes back to neutral. If Yes: control neutral improperly set (see page
35). If no: balance swashplate (see Mechanical neutral adjustment, page 37). If
you still cannot set neutral, replace control.
Table 5-7. Sluggish System Response
Item Description Action
Oil level in reservoir Low oil level causes sluggish response. Fill reservoir.
High pressure relief valves/
pressure limiter settings Incorrect pressure settings affects system reaction time. Adjust or replace high pressure relief valves.
Low prime mover speed Low engine speed reduces system performance Adjust engine speed.
Charge pressure Incorrect pressure affects system performance Measure and adjust charge pressure relief or replace charge pump.
Air in system Air in system produces sluggish system response Fill tank to proper level. Cycle system slowly for several minutes to remove air
from system.
Contaminated control orifices Control orifices are plugged. Clean control orifices.
Contaminated control screens Control screens are plugged. Clean or replace control screens.
Pump inlet vacuum Inlet vacuum is too high resulting in reduced system
pressure. Measure charge inlet vacuum. Inspect line for proper sizing. Replace filter. Con-
firm proper bypass operation.