Diagnosing Hydraulic Failure in the Hitachi EX60 Excavator

[MikePhua]

The Hitachi EX60 and Its Global Footprint
The Hitachi EX60 is a compact hydraulic excavator introduced in the late 1980s as part of Hitachi Construction Machinery’s push into the mid-size earthmoving market. With an operating weight of approximately 6 metric tons and powered by a 4-cylinder Isuzu diesel engine, the EX60 was designed for trenching, grading, and utility work in tight spaces. Its popularity surged in Asia and later spread to North America through both official and grey-market channels.
Hitachi, founded in 1910, became a global leader in hydraulic excavator technology by the 1980s. The EX series was known for its stacked hydraulic pump design, pilot-controlled joysticks, and robust undercarriage. While newer models like the ZX60 have replaced the EX60 in most fleets, thousands of units remain in service today—especially in rural and agricultural settings.

Symptoms of System-Wide Hydraulic Failure
A common issue reported with aging EX60 units is a sudden and progressive loss of hydraulic functions. The failure often begins with subtle signs—such as whining noises from the pump or sluggish swing brake response—and escalates to complete loss of control in all functions except one track.
Typical failure sequence:

• Hydraulic whine during operation
  
• Swing brake fails to release
  
• Left track stops responding
  
• Swing function ceases entirely
  
• All controls shut down except right track
  

This pattern suggests a failure in the pilot pressure system, which governs the activation of control valves. Without pilot pressure, the main hydraulic valves remain closed, rendering most functions inoperable.

Understanding the Pilot Pump and Its Role
The EX60 uses a three-pump configuration:

• Two main pumps for high-pressure hydraulic flow
  
• One small pilot pump for low-pressure control signals
  

The pilot pump draws fluid from the reservoir and sends it through a small filter to a valve block beneath the cab. This block distributes pilot pressure to the joysticks and control valves. If the pilot pump fails, the machine loses its ability to command hydraulic movement—even if the main pumps are functional.
In one case, a farmer discovered that the pilot pump shaft wasn’t turning, despite the fluid reservoir being full. Removing the pump revealed that the input shaft from the main pump had stopped rotating, suggesting a deeper mechanical failure.

Coupling Failure Between Hydraulic Pumps
The EX60’s stacked pump design relies on internal couplings to transfer rotational energy from the engine to each pump. If the coupling between the first and second main pump fails, the pilot pump—mounted at the end—may also stop receiving drive.
Signs of coupling failure:

• Shaft not rotating despite engine running
  
• No fluid output from pilot pump
  
• Right track still functions (powered by first pump)
  
• No load response when other controls are engaged
  

This type of failure is subtle and often misdiagnosed as electrical or valve-related. A technician in Ontario once spent days testing solenoids before discovering a stripped spline coupling inside the pump stack.

Final Drive Seal Leaks and Floating Seal Wear
Another issue reported in EX60 units is oil leakage behind the final drive sprocket. This is typically caused by failure of the floating seal—a mechanical face seal that prevents gear oil from escaping the travel motor housing.
Floating seal failure indicators:

• Oil seepage around sprocket hub
  
• Loss of gear oil (up to 20 gallons in severe cases)
  
• Visible damage to seal faces or O-rings
  
• Air in hydraulic system after refill
  

Floating seals can wear out due to age, contamination, or misalignment. While some last over 10,000 hours, others fail prematurely. A contractor in British Columbia replaced his seal at 4,500 hours after noticing a trail of oil during transport.

Repair Strategy and Preventive Measures
To address hydraulic and final drive issues:

• Remove and inspect pilot pump shaft and couplings
  
• Replace damaged splines or bushings in pump stack
  
• Flush hydraulic system and bleed air after repairs
  
• Replace floating seals with OEM-grade components
  
• Monitor pilot pressure using a gauge at the valve block
  
• Keep fluid reservoirs clean and sealed to prevent contamination
  

Preventive maintenance tips:

• Change hydraulic filters every 500 hours
  
• Inspect pump couplings annually
  
• Check pilot pressure monthly
  
• Replace final drive seals every 3,000–5,000 hours or during overhaul
  

Operators who follow these guidelines report fewer breakdowns and smoother control response. In one fleet, proactive coupling inspections reduced downtime by 40% over two seasons.

Conclusion
The Hitachi EX60 remains a capable and reliable excavator when properly maintained. Hydraulic failures often stem from pilot pump or coupling issues, while final drive leaks point to worn floating seals. Understanding the machine’s stacked pump architecture and pilot control logic is key to accurate diagnosis and long-term performance. Whether trenching in Mississippi or grading in Western Canada, the EX60 continues to prove that even older iron can deliver when treated with care and mechanical insight.