Daewoo Solar 420LC-V, Manual

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Page 23
Hydraulic System Troubleshooting, Testing and
Adjustment
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Pressure should stay consistently above 2.5 bar (36 psi). If pressure falls below the
recommended minimum level, forceful acceleration of the swing motor could lead to cavitation
of the circuit and stalling, slowed rotation, noise and possible damage.
2. If main inlet and outlet pressures were off in the preceding tests in Step 1, adjust swing relief valve
pressure.
Following adjustment, repeat the operating pressure tests (with gauges connected to the inlet and
outlet test ports on top of the swing motor) and check pressures with the swing locks engaged and
released.
If pressure adjustment fails to restore adequate performance, proceed to the Troubleshooting - Swing
table.
3. If pressure tests were at recommended levels through the main inlet and outlet ports, and through the
"SH" port of the swing brake, the causes of poor swing performance could include a faulty swing
motor, drive train overloading or gearbox defect, or a problem in the brake assembly or swing control
valve. Proceed to the troubleshooting information in the next procedure.
If pressure through the "SH" port was tested below the minimum 4 bar (58 psi) level, check the shuttle
valve in the rear compartment behind cabin. When pressure through the port is at the recommended
level, the brake release valve should disengage the swing brake, allowing the swing motor to rotate
the excavator. If pressure adjustment to the valve has been restored but the brake still fails to release,
the brake piston or friction plate may be frozen, requiring disassembly of the motor and parts repair/
replacement.
4. If pressure tested at the motor makeup valve falls below recommended minimum level, and
consequent problems with cavitation, stalling and surging are observed, check the restriction valve. If
pressure adjustment to the valve has been restored but if problems with cavitation continues,
disassemble the upper swing motor housing and clean or replace assembly components as required.
NOTE:
If all tested pressures are at or above recommended levels, and there are no mechanical
problems in the drive train or in the motor/brake assembly, the problem will require further
hydraulic troubleshooting. It’s also possible that a defective joystick, an intermittent short in
an electrical control circuit or a problem in the e-EPOS circuit is causing diminished swing
performance. Pull out the e-EPOS indicator panel from underneath the operator’s seat
and perform the self-diagnosis test. If the display panel reads code "0.2," it is reporting
that the swing priority proportional valve is not functioning, except in the minimum "fail-
safe" mode. Refer to the Electrical section of this book for more information.