How to Diagnose a Bad Hydraulic Pump in Excavators: Repair vs Replace Guide

Slow and Weak Operation:

• All or specific functions (bucket, boom, travel, swing) are noticeably slower, even at high engine RPM.

• Lack of digging or lifting force, feels "sluggish" or "spongy".

Erratic or No Movement:

• Complete failure of one or more functions.

• Jerky, stuttering, or "crawling" (unsteady) movement.

• Uncontrolled movement (e.g., boom drifting down).

Unusual Noises:

• High-pitched whining, buzzing, knocking, or rattling sounds near the pump, especially under load. This indicates internal wear (e.g., valve plate, pistons, bearings) or cavitation.

Abnormal Oil Temperature:

• Hydraulic oil temperature rises too quickly or remains excessively high (exceeding normal operating range, typically >80°C/176°F is a warning sign). Severe internal leakage or wear increases friction, reducing efficiency and generating heat.

Abnormal Pressure:

• Low Main Pump Pressure: Measured pressure at the pump outlet is below specification (check service manual).

• Excessive Pressure Fluctuation: Pressure gauge needle oscillates wildly.

• Failure to Build Pressure: System cannot reach required pressure.

Abnormal Hydraulic Fluid:

• Presence of excessive metal particles (copper, iron/grey) or fluid is unusually murky/milky. This is strong evidence of severe internal pump wear.

• Severe foaming of the fluid (often accompanied by noise indicating aeration).

External Leaks:

• Persistent, visible hydraulic oil leaks at pump body joints or the shaft seal. While leaks themselves don't mean the pump core is bad, prolonged leaks can cause damage due to low oil and need fixing.