H-13 Hydraulic Drift Of Arm Is Large - Komatsu PC88MR-10 Shop Manual

40 Troubleshooting
Troubleshooting of hydraulic and mechanical system (H-
mode)

H-13 Hydraulic drift of arm is large

Hydraulic drift of arm is large.
Failure
Related
Perform all troubleshooting with working mode set in power (P) mode.
information
No. Cause
Defective arm cylinder
1
Malfunction of arm
control valve (suction-
2
safety valve) (arm IN
side)
Malfunction of arm
3
control valve (spool)
40-484
(PC88MR-MS4-400-A-Z0-A)
Procedure, measuring location, criteria, and remarks
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Leakage from arm
cylinder
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Arm relief pressure
a Among above relief pressures, if only arm IN relief pressure is low,
suction-safety valve may be defective.
Check that check valve of suction-safety valve is seated on valve body in
position (it is not stuck halfway).
a Since relief pressure cannot be adjusted with safety valve installed on
machine, replace safety valve assembly if safety valve is found to be
defective.
a Release remaining pressure from hydraulic tank and piping, and then
perform troubleshooting with engine stopped.
Check for stuck or seized arm spool in control valve body.
(Spool must move smoothly and must not be caught.)
Remove arm spool from valve body and check it for defects and dirt.
Arm IN hydraulic relief
Arm IN hydraulic relief
Max. 7.5 cc/min
26.5 MPa
{270 ± 15 kg/cm 2 }
PC88MR-10