Komatsu PC88MR-10 Shop Manual page 986

40 Troubleshooting
Troubleshooting of hydraulic and mechanical system (H-
mode)
No. Cause
Malfunction of travel
control valve (pressure
compensation valve)
10
(R.H. travel FORWARD
side)
Malfunction of travel
control valve (pressure
compensation valve)
11
(R.H. travel REVERSE
side)
Malfunction of travel
control valve (pressure
compensation valve) (L.
12
H. travel FORWARD
side)
Malfunction of travel
control valve (pressure
compensation valve) (L.
13
H. travel REVERSE
side)
Malfunction of travel
control valve (suction
14
valve)
Defective center swivel
15
joint
Defective R.H. travel
16
motor (safety valve)
Defective L.H. travel
17
motor (safety valve)
Defective R.H. travel
18
motor (check valve)
40-498
Procedure, measuring location, criteria, and remarks
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Travel relief
R.H. travel FORWARD hydraulic
pressure
a If only 1 place of right, left, forward, and reverse is abnormal, pressure
compensation valve may malfunction.
Interchange pressure
REVERSE sides, and check whether failure symptom changes.
a If relief pressures of R.H. travel FORWARD and L.H. travel REVERSE are
the same and low, main relief valve of rear pump may malfunction. Check
arm relief pressure additionally.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Travel relief
R.H travel REVERSE hydraulic
pressure
If measured values in checks on causes (10) and (11) are the same and low,
main relief valve of rear pump may malfunction. Check arm relief pressure
additionally.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Travel relief
L.H. travel FORWARD hydraulic
pressure
If relief pressures of L.H. travel FORWARD and L.H. travel REVERSE are
same and low, main relief valve of front pump may malfunction. Check bucket
relief pressure additionally.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Travel relief
pressure
If measured values in checks on causes (12) and (13) are same and low,
main relief valve of front pump may malfunction. Check bucket relief pressure
additionally.
If relief pressure of only 1 port is low after adjusting relief valve, suction valve
may malfunction.
Check suction valve (check valve) for defects and fatigue of spring.
Connect hoses from L.H. and R.H. travel motors to swivel joint changing
connecting ports with each other, and check whether direction in which
machine deviates changes.
If relief pressures of both R.H. travel FORWARD and REVERSE or those of
R.H. travel FORWARD and REVERSE are unusual in checks on causes (10)
and (11) respectively, respective safety valves are probably defective.
Interchange safety valves of L.H. and R.H. travel motors, and check whether
failure symptom changes.
If relief pressures of both L.H. travel FORWARD and REVERSE are unusual
in checks on causes (12) and (13) respectively, respective safety valves may
be defective.
Interchange safety valves of L.H. and R.H. travel motors, and check whether
failure symptom changes.
If pressure compensation valves are found to be normal in checks on causes
(10) and (11), check valves may malfunction.
Interchange check valves on FORWARD and REVERSE sides of same travel
motor, and check whether failure symptom changes.
relief
compensation valves
relief
relief
L.H. travel REVESE hydraulic
relief
3.48 (+2.0/-1.5) MPa
{355 (+20/-15) kg/
cm 2 }
on FORWARD and
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
PC88MR-10