Service Manual User Manual

Section 9
9-122
27. Cylinder movement is
jerky.
1. Air trapped in cylinder or in
hydraulic line. Low oil level in
hydraulic oil reservoir.
2. Binding of cylinder rod or piston.
3. Rod seal installed improperly.
4. Binding of bearing at base end
or rod end.
5. Defective counterbalance
cartridge (hoist/lower cylinder).
1. Inspect fluid for foam or
bubbles. Check and tighten
connections. Bring hydraulic
fluid up to operating
temperature and cycle vehicle
functions several times through
full range of motion to remove
(purge or “bleed”) air from
system.
2. Repair or replace cylinder.
3. Replace seal. Properly install
new seal.
4. Eliminate bind and repair or
replace bearing and other
components as required.
5. Replace counterbalance
cartridges.
28. Cylinder movement is
slow or sluggish; cycle
times are slow.
1. Control valve not fully shifted.
2. Internal leakage or binding
within cylinder.
3. Insufficient flow of oil.
4. Unloader valve malfunction.
5. Pilot valve malfunction.
1. Engage control valve fully.
Check that valve pressures are
set as specified and that
applicable circuit hoses are not
restricted, bent, kinked,
damaged, etc.
2. Repair or replace cylinder.
3. Check flow throughout hydraulic
circuit, starting at main pump.
4. Check and replace as required.
5. Check and replace as required.
29. Cylinder piston rod drifts
or creeps.
1. Worn piston seals.
2. Tube is out-of-round.
1. Install new seal kit.
2. Replace tube.
30. Main relief valve doesn’t
hold pressure setting.
1. Spring is broken or worn (“has
taken a set”).
2. Poppet stuck due to dirt or
deposits.
1. Replace relief valve assembly.
2. Replace relief valve assembly.
Hydraulic System Troubleshooting
Problem Cause Remedy
Model 3606 • Origin 10/99