Komatsu PC88MR-10 Shop Manual page 965

No. Cause
Malfunction of bucket
control valve (pressure
6
compensation valve)
(bucket DUMP side)
Malfunction of bucket
control valve (suction-
7
safety valve) (bucket
CURL side)
Malfunction of bucket
control valve (suction-
8
safety valve) (bucket
DUMP side)
Defective bucket
9
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.
Bucket relief
pressure
a Check hydraulic drift of bucket cylinder with engine stopped.
Hydraulic oil temperature: Within
bucket empty, arm cylinder fully
Hydraulic drift
a Check whether bucket cylinder moves slowly when performing hydraulic
relief of other work equipment. (If bucket 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.
Bucket relief
pressure
If bucket CURL relief pressure is low, suction 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.
Bucket relief
pressure
If bucket DUMP relief pressure is low, suction 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
bucket cylinder
Bucket DUMP hydraulic relief
operating range,
retracted, bucket cylinder fully
retracted, boom top face
horizontal
Bucket CURL relief
Bucket DUMP hydraulic relief
Bucket CURL 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
40-477