Excavator hydraulic pump 21W-60-22111 Komatsu PC75UU-2 PC75UD-2 Main piston pump

The main pump is an A10VD43 variable displacement piston pump fitted with a tandem gear pump. Primary failure causes for this legacy model include contaminated hydraulic fluid, suction-side air ingress, and seized regulator assemblies.

External factors: Blocked suction filter, suction line air leakage, metallic particulates in hydraulic fluid.

Diagnosis: Excessive case drain flow indicates internal pump wear.

• High-pitched squeal (Cavitation): Inadequate suction or air entrainment; milky, foamy hydraulic fluid.
• Metallic tapping: Failed bearing / ball joint assembly, misaligned coupling.

Diagnostic: Isolate regulator control oil supply. If lugging ceases, the regulator is defective.

Risk: A compromised seal will draw in air, inducing cavitation and accelerating pump deterioration.

1. Inspect hydraulic fluid condition, fluid level, suction filter and suction hose
2. Measure maximum main pump pressure and pilot pressure; cross-reference with service manual specifications
3. Take pump case drain flow readings
4. Disassemble and clean regulator; inspect spring integrity
5. Verify coupling concentricity

• Minor wear: Lap valve plate, renew pistons, piston shoes, ball joint and seal kit; perform regulator cleaning.
• Severe scoring: Fit new or remanufactured complete pump assembly.
• Post-repair: Replace all hydraulic filters and thoroughly clean the hydraulic tank.