HPK055 Hitachi ZAX120-3 ZX120-3 ZX135US-3 Hydraulic Main Piston Pump Assembly 9290597 9285566

HPK055 hydraulic main piston pump assembly designed for Hitachi ZAX120-3, ZX120-3, and ZX135US-3 excavators. Compatible with OEM part numbers 9290597 and 9285566. This assembly includes the pump body, regulator, and servo valve components, providing a complete replacement solution for the main hydraulic system.

• Verify the OEM part number to confirm the main hydraulic piston pump assembly fits, including the pump body, regulator, and servo valve components.
• New or remanufactured pumps must be supplied with a hydraulic bench test report covering pressure, flow, case drain, and internal leakage.
• For remanufactured pumps, confirm the new replacement of pistons, cylinder block, valve plate, slippers, retainer plate, bearings, and all seals.
• Inspect the pump housing for cracks and sand holes upon arrival. Keep port threads intact and seal ports to prevent contaminant entry.
• Secure the pump during transportation to avoid impact damage to the input shaft, ports, and precision valve parts.
• Clean the hydraulic tank and pipelines before installation, replace all hydraulic filters, and bleed air from the hydraulic system.
• Test pump pressure, flow, and regulator response after installation. Check for abnormal noise, overheating, oil leakage, engine bogging, and weak operation.