Troubleshooting - Control Valve - Doosan DX140R Shop Manual

TROUBLESHOOTING –
CONTROL VALVE
Check control valve problems only after other hydraulic circuit
operational tests have
"Troubleshooting Baseline
Pump flow, pilot pressure, Negacon pressure, main relief
pressure, and port relief pressure should all be checked before
starting to work on the control valve. Make sure the hydraulic
system is topped up to the required level and free of oil leaks or
air in the system that could cause cavitation problems.
Problem
Main relief valve.
Cylinder goes down in spool
neutral.
Cylinder drops before start
at boom up operation.
Slow operation or response.
Swing priority not operating
correctly.
Boom and arm cylinders do
not perform normally in
combined operation.
Relief valve malfunctions:
Hydraulic System Troubleshooting, Testing and Adjustment
been made. Refer
Recommendations" procedure.
Possible Cause
Particulate contamination.
Broken or damaged spring.
Adjusting screw loose.
Main poppet sticking.
Clogged orifice in pilot passage to
control valve.
Excessive clearance between
casing and spool.
Spool does not return to neutral/
sticking spool.
Spool does not return to neutral
because of dirt or other
contaminants.
Broken or damaged spring.
Main relief or port relief not
operating properly.
Impurities in pilot circuit.
Rod check valve damaged or
clogged.
Poppet sticking.
Broken or damaged spring.
Excessive clearance between spool
or casing.
Sticking spool.
Broken or damaged spring.
Main or port relief valve damaged.
Sticking spool.
Solenoid valve faulty.
Priority valve faulty or spool
sticking.
Broken or deformed spring.
Excess clearance between right
and left casing and valve spool.
Clogged spool passage.
to the
Disassemble, clean main poppet.
Replace.
Readjust.
Repair/replace.
Clean/replace.
Replace spool or casing.
Check secondary pilot pressure.
Clean.
Replace.
See above.
Clean.
Clean/replace.
Clean/replace.
Replace.
Check pilot pressure and/or replace
spool or casing.
Clean/replace.
Replace.
Check pressure/replace.
Clean/replace.
Replace.
Check pilot pressure.
Replace.
Clean/replace.
Clean/replace, replace filter.
Remedy
SP001942
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