5-20
YES
OK
YES
YES
NO
NO
NO
Is genuine
hydraulic oil or
equivalent being
used?
Is not hydraulic
oil temperature
high?
Does the symptom
change when port
relief valve is
replaced with
normal valve?
BOOM, ARM OR BUCKET CYLINDER EXTENDS OR CONTRACTS ITSELF AND
ATTACHMENT FALLS
3)
Normal
Port relief valve is
faulty.
ͽ
Control valve's
return spring is
faulty.
Pressure
tightness
between control
valve casing and
spool is poor.
Contact surface
between poppet
and seat is poor.
Cylinder is faulty.
Disassemble
and repair or
replace.
Disassemble
and replace.
Locate the cause
of hydraulic oil
temperature rise
and lower it to
proper level.
Replace with
genuine
hydraulic oil or
equivalent.
Disassemble
and repair.
Disassemble
and repair.
Disassemble
and repair.
ͽ
Is cylinder internal
leakage within
standard level?
Abnormal
Abnormally high.
Is control valve
return spring
normal?
Disassemble and
inspect check
valve in hydraulic
circuit and check
for any fault.
Cause
Remedy
YES
NO
