Doosan DX225LC-3, Shop Manual

Page: 117 / 878

SP002454
Page 9
General Maintenance Instructions
MAINTENANCE SERVICE AND
REPAIR PROCEDURE
General Precautions
Fluid level and condition should always be checked whenever
any other maintenance service or repair is being performed.
NOTE: If the unit is being used in an extreme temperature
environment (in subfreezing climates or in high
temperature, high humidity tropical conditions),
frequent purging of moisture condensation from the
hydraulic reservoir drain tap should be a regular and
frequent part of the operating routine. In more
moderate, temperate climates, draining reservoir
sediment and moisture may not be required more
than once or twice every few months.
Inspect drained oil and used filters for signs of abnormal coloring
or visible fluid contamination at every oil change. Abrasive grit or
dust particles will cause discoloration and darkening of the fluid.
Visible accumulations of dirt or grit could be an indication that
filter elements are overloaded (and will require more frequent
replacement) or that disintegrating bearings or other component
failures in the hydraulic circuit may be imminent or have already
occurred. Open the drain plugs on the main pump casings and
check and compare drain oil in the pumps. Look for evidence of
grit or metallic particles.
Vibration or unusual noise during operation could be an
indication of air leaking into the circuit (Refer to the appropriate
Troubleshooting section for component or unit for procedures.),
or it may be evidence of a defective pump. The gear type pilot
pump could be defective, causing low pilot pressure, or a main
pump broken shoe or piston could be responsible.
NOTE: If equipped, indicated operating pressure, as shown
on the multidisplay digital gauge on the Instrument
Panel ("F-Pump" and "R-Pump") will be reduced
because of a mechanical problem inside the pump.
However, pressure loss could also be because of
cavitation or air leakage, or other faults in the
hydraulic system.
Check the exterior case drain oil in the main pumps. If no
metallic particles are found, make sure there is no air in the
system. Unbolt and remove tank return drain line from the top
part of the swing motor, both travel motors and each main pump.
If there is air in any one of the drain lines, carefully prefill the
assembly before bolting together the drain line piping
connections. Run the system at low rpm.