jcb JS300 Service Manual page 908

Item Symptoms Related Parts
4-2 Inner oil Piston seal
leakage.
Piston rod
Cylinder tube
extends
when work
stops or
lowers
abnormally
during work.
Also,
Piston Nut
specified
operating
speed is not
achieved.
Note: Note: Hydraulic oil expands and contracts due to changes in temperature and pressure. Accordingly, the ram
also expands and this can be mistaken for internal leakage. When inspecting for internal leakage, do so at set
conditions
4-3
4
4-4 Heavy Pin bushing, Pin Gap between installation part
shock
loading when
changing
from
extension to
retraction
and back
4-5 Noisy Oil supply
operation
Pin bushing, Pin Scuffing at connecting part
Note: If left in the state where operation is poor, the ram will no longer move and other parts will be affected
adversely. Inspect early and carry out appropriate measures.
E-247
Trouble
Scratches, wear are present
Scratches, rust on the inside
Loose nut
Valves Leak from valve
Air Air remaining inside ram
Operation is unsteady
and pin bushing is too large
Insufficient oil
Hydraulic System Fault Finding
Replace with new part. Inspect the cylinder
tube inner surface.
Remove the scratches/rust by honing or
with an oil stone and make the surfaces
smooth.
If the scratch is deep and cannot be
repaired, replace the cylinder
Replace piston seal.
Tighten to specified torque
Inspect the valve leakage amount and service.
Bleed the air. For rams that do not have an
airbleeder, operate back and forth several
times at low pressure and low speed to bleed
the air. For rams with an air bleeder, remove
the load to reduce the pressure then loosen the
air bleeder and completely bleed the air.
Note: The ram may expand if it is stopped
suddenly. This is due to the compression of the
hydraulic oil. This occurs especially with long
stroke rams.
Measure the pin and pin bushing and replace
parts if measurements exceed the
specifications.
Add oil.
Replace with new part and add oil.
9813/5100-1
Section E - Hydraulics
Hydraulic Rams
Treatment
E-247