Komatsu PC88MR-10 Shop Manual page 963

No. Cause
Malfunction of arm
control valve (pressure
7
compensation valve)
(arm OUT side)
Malfunction of arm
control valve (suction
8
valve) (arm OUT side)
Malfunction of arm
control valve (suction-
9
safety valve) (arm IN
side)
10 Defective arm cylinder
PC88MR-10
Troubleshooting of hydraulic and mechanical system (H-
Procedure, measuring location, criteria, and remarks
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Arm relief pressure
a Check hydraulic drift of arm cylinder with engine stopped.
Hydraulic oil temperature: Within
operating range, bucket with rated
Hydraulic drift
load, arm cylinder fully retracted
a Check whether arm cylinder moves slowly when performing hydraulic
relief of other work equipment. (If arm cylinder moves, it is abnormal.)
a If any failure is found in either of above check items, interchange pressure
compensation valves on bucket CURL and DUMP sides, and check
whether failure symptom changes.
(Each area ratio is different, so be sure to restore it after checking the
symptom.)
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Arm relief pressure
a If arm OUT relief pressure is low, suction valve (check valve) may be
defective. Check it.
Check that check valve is seated on valve body in position (it is not stuck
halfway).
Remove check valve from valve body and check it for defects and dirt.
Check spring for setting and deformation.
Take care not to let foreign matter enter valve when re-installing spool.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Arm relief pressure
a If arm IN relief pressure is low, suction-safety valve may be defective.
Check it.
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 Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Leakage from arm
cylinder
Arm OUT hydraulic relief
Arm OUT hydraulic relief
Arm IN hydraulic relief
Arm IN hydraulic relief
40 Troubleshooting
mode)
26.5 ± 1.5 MPa
{270 ± 15 kg/cm 2 }
If visible hydraulic
drift is observed, it is
abnormal.
26.5 ± 1.5 MPa
{270 ± 15 kg/cm 2 }
26.5 ± 1.5 MPa
{270 ± 15 kg/cm 2 }
Max. 7.5 cc/min
40-475