Komatsu PC88MR-10 Shop Manual page 969

No. Cause
Malfunction of blade
control valve (RAISE
6
side)
Malfunction of boom
RAISE (suction-safety
7
valve)
Malfunction of blade
LOWER (suction-safety
8
valve)
Defective blade cylinder
9
10 Defective gear pump
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.
Blade relief pressure
a Check hydraulic drift of bucket cylinder with engine stopped.
Hydraulic oil temperature: Within
Hydraulic drift
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Blade relief pressure
If blade RAISE 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.
Blade relief pressure
If blade LOWER 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
Performance deterioration, malfunction, and internal defect of the gear pump
may be occurred. Check it directly.
Blade RAISE relief
the operating range, fully
retracted blade cylinder, fully
retracted arm cylinder, fully
retracted bucket cylinder, and
boom top face horizontal
Blade RAISE relief
Blade LOWER relief
Blade LOWER relief
40 Troubleshooting
mode)
12.7 ± 1.5 MPa
{135 ± 15 kg/cm 2 }
If visible hydraulic
drift is observed, it is
abnormal.
12.7 ± 1.5 MPa
{135 ± 15 kg/cm 2 }
21.1 ± 1.5 MPa
{215 ± 15 kg/cm 2 }
Max. 7.5 cc/min
40-481