
5-18
OK
NO
YES
YES
YES
NO
NO
Are LH/RH travel
operations
possible?
Does the
symptom change
when port relief
valve is replaced
with other valve?
Inspect if pilot
piping is not
clogged or oil is
not leaking from
the piping.
Disassemble
main relief valve
and check if it is
not irregular.
Are other
attachments
operatable?
Inspect oil
volume in
hydraulic oil tank.
Is MCV pilot
pressure within
standard level?
Is gear pump pilot
pressure within
standard level?
Is gear pump
delivering oil?
Particles present
OK
Faulty
Port relief valve is
faulty.
ͽ
Pilot valve is
faulty.
Pilot relief valve is
faulty.
Gear pump is
broken.
Hydraulic pump is
broken.
Main relief valve
is defective.
Coupling at pump
connection is
broken.
Cylinder interior is
broken.
Control valve
spool is stuck.
Disassemble
and repair or
replace.
Disassemble
and repair.
Disassemble
and repair or
replace.
Disassemble
and repair.
Disassemble
and repair.
Disassemble
and repair or
replace.
Disassemble
and repair.
Replenish
hydraulic oil.
Disassemble
and repair.
Disassemble
and repair.
ͽ
Remove dust plug
under engine
flywheel and
check if coupling
element particles
are not present.
6
6. ATTACHMENT SYSTEM
BOOM OR ARM ACTION IS IMPOSSIBLE AT ALL
1)
Short
Does control
valve spool move
lightly by hand?
Cause
Remedy
YES
YES
YES
NO
NO
OK
NO
YES