Komatsu PC88MR-10 Shop Manual page 967

No. Cause
Malfunction of boom
swing control valve
(pressure
6
compensation valve)
(left swing side)
Malfunction of boom
swing control valve
7
(suction-safety valve)
(right swing side)
Malfunction of boom
swing control valve
8
(suction-safety valve)
(left swing side)
Defective boom swing
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.
Boom swing relief
pressure
a Check whether boom swing cylinder moves slowly when performing
hydraulic relief of other work equipment. (If boom cylinder moves, it is
abnormal.)
a If any failure is found in either of above check items, interchange pressure
compensation valves on right and left swing 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.
Boom swing relief
pressure
If boom swing right 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.
Boom swing relief
pressure
If boom swing left 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
Boom swing left relief
Boom swing right relief
Boom swing left relief
Boom swing right relief
40 Troubleshooting
mode)
26.5 ± 1.5 MPa
{270 ± 15 kg/cm 2 }
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
40-479