Exploring technical solutions to eliminate abnormal noise from the main pump of an excavator

2025-09-04

We began to analyze the abnormal noise from the main pump of the excavator and believed it was caused by pump cavitation or air entrainment in the oil circuit. Therefore, we first adjusted the operating equipment to the oil level detection position and found that the oil level in the hydraulic oil tank was below the lower limit of the oil gauge, indicating a lack of oil. Upon inquiring with the driver, we learned that the seal ring of the high-pressure oil pipe leading to the rodless chamber of the stick cylinder had been replaced due to oil leakage during operation, but the oil level was not checked promptly after replacement. Therefore, we first refueled the hydraulic oil tank to the standard oil level. The test machine indicated that although the abnormal noise had decreased, it still existed. Then, we exhausted the main pump through its exhaust valve and tested the machine again, but the abnormal noise still persisted, indicating that this noise could not be entirely caused by pump cavitation.

Next, both the suction filter element and the return filter element of the hydraulic oil tank were inspected, and it was found that the suction filter element had turned black and contained oil sludge, while the return filter element had brown metal particles adhering to it. Therefore, these filter elements were replaced. Considering the presence of brown metal particles on the return filter element, the oil in the main pump was drained and inspected, and brown metal particles were also found. During the inspection of the main pump, it was found that the piston, port plate, swash plate, etc. were not damaged, but the sliding shoe was worn. After replacing it, the assembly was carried out strictly according to requirements, the hydraulic system was cleaned, and the oil was changed. When the machine was restarted for testing, the abnormal noise disappeared, and the fault had been eliminated.

Typically, the possible causes of abnormal noise occurring around the main pump of an excavator are as follows:

The hydraulic oil is insufficient, causing the main pump to suck air; air is mixed into the suction pipeline; the suction filter element is blocked, leading to air suction in the main pump; the internal wear of the main pump causes abnormal noise during operation.

The abnormal noise of the excavator's main pump is attributed to two reasons: the quality of the hydraulic oil and the wear of the sliding shoes inside the main pump. The reason is that after replacing the seals, the oil level was not checked in time, resulting in insufficient hydraulic oil, which caused the main pump to experience cavitation. When the oil mixed with air flows through the main pump, the sliding shoes may not float up or may not float up sufficiently at certain moments, preventing an excellent smooth oil film from being formed between the sliding shoes and the swash plate. This leads to wear of the sliding shoes, ultimately causing abnormal noise during the operation of the main pump.