Slow machine movement, weak digging power: Performance worsens when hot due to wear of internal plungers, slippers, and valve plate causing increased internal leakage and excessive case drain flow.
Engine lugging and speed drop under load: Caused by stuck power control spool or faulty servo piston preventing normal displacement reduction, leading to torque exceeding engine output.
Abnormal noise, whistling and pipeline vibration: Results from clogged suction filter, air entering suction line causing cavitation, damaged bearings, or contaminated hydraulic oil with metal debris.
Overheating of hydraulic system: Caused by heavy internal leakage converting pressure loss into heat, stuck regulator maintaining large displacement, or aged seals resulting in oil leakage.
Abnormal control of regulator/solenoid valve: Erratic movement due to stuck spool, damaged coil of EPC solenoid valve, or abnormal pressure feedback circuit disturbing pump displacement control.
External leakage of pump body: Caused by aged main shaft seal, damaged housing O-rings, porosity or cracks on pump housing, accelerated by high temperature and hydraulic contaminants.
Procurement Recommendations
Test case drain flow, main pressure and EPC control current first to differentiate electrical/regulator faults from mechanical wear, avoiding unnecessary purchase of complete pump assembly.
Minor wear: Procure full repair kit including plungers, slippers, valve plate, and seals plus regulator assembly.
Severe scoring: On cylinder block and swashplate, consider high-quality rebuilt pump or new hydraulic pump assembly for tight schedules. Confirm pump part number 708-1G-00014 / 708-1G-11510 and nameplate information before ordering.
Supporting purchase: Replace hydraulic return filter and pilot filter simultaneously, inspect hydraulic oil to prevent new parts from being damaged by contaminants.