Vehicle System
Disassembly & Assembly
79
Cause and Measure on failure of
control valve
Problem: External leakage form dust seal
Cause
1.
damaged seal lip or seal worn away.
2.
damaged spool.
3.
contaminated seal plate.
4.
higher back pressure of tank port.
5.
penetraed foreign material such as paint and
dirt.
Measure
1.
exchange dust seal.
2.
exchange control valve section ass’y.
3.
disassemble seal plate, and clean seal plate
and tighten it by a standard torque.
4.
Investigate hose or exchange return filter.
5.
Clean it. Be careful not to damage spool.
Problem: Inappropriate Spool motion
Cause
1.
foriegn material penetrates into spool.
2.
deformation of spool by exteranl force.
3.
bias wear of spool by biased force.
4.
loosening of cap bolt.
5.
high oil temp.
6.
low oil temp.
Measure
1.
take spool out, and clean it.
2.
exchange valve section ass’y.
3.
exchange valve section ass’y.
4.
tighten cap boly by standard torque.
5.
Use in normal temperature.
6.
Use in normal temperature.
Problem: large drift of cylinder
Cause
1.
internal leakage of spool damage.
2.
leakage of port relief valve and shut-off plug.
3.
bias of spool position(not neutal position).
4.
leakage of cylinder.
Measure
1.
change control valve section ass’y.
2.
check if O-ring is normal. Or exchange it.
3.
check an interference of lever link.
4.
Check a cylinder.
Problem: lower pressure(not to lift a load)
Cause
1.
contaminated relief valve.
2.
strange wearing of relief valve poppet.
3.
lower relief setting pressure.
4.
O-ring damage of relief valve.
5.
Damaged pump.
Measure
1.
overhaul relief valve ass’y. Clean its
internalparts.
2.
Exchange relief valve ass’y.
3.
Adjust relief setting pressure to normal value.
4.
Exchange O-ring.
5.
Exchange pump.
