Doosan DX140LCR, Shop Manual

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SP001942 Hydraulic System Troubleshooting, Testing and Adjustment
Page 30
TROUBLESHOOTING – SWING
GEARBOX
Problem Possible Cause Remedy
Swing motor fails to operate and:
Three pressure tests at
motor, brake or makeup
valve show low reading(s). Swing relief valve defective Brake
release valve defective Motor
makeup valve defective. Adjust pressure to recommended range
in affected valve.
OR
Disassemble and clean valve assembly.
Replace all valve components that show
damage.
All three pressure checks
are OK but left travel also
fails to run. Exchange front and rear pump inlet
and outlet hoses to test pump
function. If swing and left travel are restored but
right travel stops working, replace or
repair P1 pump.
All three pressure tests are
OK, but machine fails to
swing at all. Brake assembly or motor friction
plate failing to release. Check for binding. Disassemble and
repair.
Pilot (control) pressure low or swing
control valve stuck. Disassemble / Repair pilot pressure
swing spool (305) and / or swing control
valve.
Swing motor defective. Test motor drain rate. Replace / Repair
motor.
Gear train defective. Refer to "Swing Gear Troubleshooting"
procedure.
Swing functions but only at
reduced rpm. Causes listed above could also
produce dragging swing, OR hot or
wrong oil OR worn-out parts. Check above list; then replace oil, test
motor drain rate and check for "03"
reading (e-EPOS self-test).
Left travel speed is also
reduced. Low output at P1 pump or external
pilot piping leaks/is clogged. Clean and repair piping or repair or
replace pump P1.
Swing control movement is
reversed. Inlet / outlet piping reversed. Reset controls or reverse piping.
Machine swings but
continues coasting on past
stopping point. Swing control valve spool not
centered. Replace return spring; clean/ repair
valve piston and spool.
Pilot pressure may be outside
range. Disassemble, clean or replace pilot relief
valve or pilot valve.
Swing relief valve may be faulty. Repair/Replace swing relief valve.
Swing movement is in one
direction only. Check to see that pilot pressure is
the same right and left. If pilot pressure is unequal, clean or
repair piping or repair/replace valve.
Swing control valve spool may be
stuck. Repair/Replace the swing control valve.
Swing relief valve may be faulty. Repair/Replace the swing relief valve.
No rotation and:
Pressure at swing motor
inlet increases. Swing brake not releasing. Check brake engagement and
disengagement; check release pressure.
Internal damage to gearbox drive
train. Replace broken gears and drive train
assemblies.
Overload. Reduce load weight.