H-12 Hydraulic Drift Of Boom Is Large - Komatsu PC88MR-10 Shop Manual

H-12 Hydraulic drift of boom is large

Hydraulic drift of boom is large.
Failure
Related
Perform all troubleshooting with working mode set in power (P) mode.
information
No. Cause
Defective boom cylinder
1
Malfunction of boom
control valve (safety
2
valve for lock valve)
Malfunction of boom
control valve (lock
3
valve)
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.
Leakage from boom
cylinder
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Boom relief pressure Boom RAISE hydraulic relief or
and arm relief
pressure
a Among above relief pressures, if arm OUT relief pressure and boom
RAISE relief pressure is low, safety valve may be defective. Check safety
valve for damaged sealing material.
a When disassembling the safety valve, replace the safety valve assembly
with a new one since its relief pressure cannot be adjusted on the
machine.
Check that pilot piston and poppet are seated on lock valve body in
position (they are not stuck halfway).
Check for stuck or seized pilot piston and poppet in lock valve body (pilot
piston and poppet must move smoothly).
Remove pilot piston and poppet from valve body and check them for
defects and dirt.
Check poppet spring for fatigue and deformation.
(PC88MR-MS3-400-A-Z0-A)
Boom RAISE hydraulic relief
arm IN hydraulic relief or arm
OUT hydraulic relief
40 Troubleshooting
mode)
Max. 7.5 cc/min
26.5 MPa
{270 ± 15 kg/cm }
2
40-483