Repair of the hydraulic pump in the Hitachi ZX140W excavator
In today's material, we present the diagnostic and repair process of the hydraulic pump in the Hitachi ZX140W wheeled excavator of the third series from 2008. The machine came to us with several serious problems: numerous oil leaks, a characteristic knocking sound when shutting down the engine, and a drop in pressure on pump P1.
Dismantling and initial diagnosis
The first step was to drain the oil, dismantle the filters and the covering elements to access the pump. Right from the start, it turned out that the coupling insert connecting the pump to the flywheel was damaged, which explained the audible knocking. The pump itself required thorough verification, so it went to the workshop.
Disassembly of the Hitachi HPV 118 hydraulic pump
After washing, we proceeded to disassemble the pump. The biggest problem revealed itself in the control piston section and the closing plate – the leakage was causing a loss of pressure, resulting in a drop in efficiency.
During the inspection, we also checked:
- the condition of the shafts and bearings,
- the condition of the auxiliary gear pump,
- the operation of the regulators.
The identified damages clearly indicated the need to replace the closing plate, control pistons, and the complete set of seals.
Assembly and new components
As part of the repair, we used:
- a new closing plate with control pistons,
- a new seal kit and O-rings,
- replacement of the auxiliary pump, which was significantly worn out.
Each component was installed using the appropriate safeguards, adhesives, and tools. As a result, the pump could be assembled fully in accordance with the manufacturer's requirements.
Bench tests
The finished pump was mounted on the test stand. During load tests, we achieved a pressure of 400 bar on both pump P1 and P2. This confirmed that the performance issue had been completely resolved.
Installation and tests in the machine
After testing, the pump returned to the Hitachi ZX140W. During installation, we additionally replaced 15 hydraulic hoses and performed sealing of the rotation column and distributor.
After field tests, which included driving, arm operation, and digging, the pressures of both pumps maintained at 350 bar. The machine regained full functionality and was returned to the client for further work.
Summary
The repair of the hydraulic pump in the Hitachi ZX140W demonstrated how crucial comprehensive diagnostics and attention to detail are. In this case, minor leaks and worn components led to significant drops in efficiency. Thanks to the replacement of the closing plate, auxiliary pump, and the entire seal kit, the machine was restored to full functionality.
The entire video can be viewed here.
