Diagnosing Hydraulic and Electrical Failures on the Hitachi EX60

[MikePhua]

The EX60 and Hitachi’s Compact Excavator Legacy
The Hitachi EX60 hydraulic excavator was introduced in the early 1990s as part of Hitachi’s compact equipment lineup, designed for urban construction, utility trenching, and landscaping. With an operating weight around 13,000 pounds and powered by a four-cylinder Isuzu diesel engine, the EX60 offered a balance of maneuverability and digging power. Its popularity spread across Asia, Europe, and North America, with thousands of units sold and many still in operation today.
Hitachi Construction Machinery, founded in 1970, became a global leader in hydraulic excavator technology, pioneering electronic control systems and efficient hydraulic circuits. The EX60 was among the first compact models to feature integrated electronics for engine and hydraulic management, which—while innovative—can become a source of troubleshooting complexity as machines age.
Terminology Notes

• Pilot Pressure: Low-pressure hydraulic signal used to control main valves and actuators.
  
• Solenoid Valve: An electrically actuated valve that opens or closes hydraulic flow based on input signals.
  
• Travel Motor: Hydraulic motor that drives the tracks, enabling forward and reverse movement.
  

Symptoms of System Failure
Operators may encounter:

• No hydraulic response from boom, arm, or bucket
  
• Engine starts but machine does not move or dig
  
• No travel function despite engine running normally
  
• Warning lights or monitor display not functioning
  
• Clicking sounds from solenoids but no hydraulic actuation
  

A technician in Malaysia shared how an EX60 arrived on site with full engine power but zero hydraulic movement. After checking pilot pressure and solenoid signals, they discovered a failed ground connection behind the cab that had disabled the entire control system.
Root Causes and Diagnostic Strategy
When an EX60 loses hydraulic and travel function simultaneously, the issue often lies in the electrical control system or pilot circuit. Common causes include:

• Blown Fuse or Relay Failure
  • Disables solenoid valves and pilot signal generation
    
  • Diagnosed by checking fuse box and relay continuity
    
• Faulty Key Switch or Ignition Circuit
  • Prevents power from reaching control modules
    
  • Confirmed by testing voltage at solenoid terminals
    
• Broken Ground Wire or Corroded Connector
  • Interrupts return path for electrical signals
    
  • Detected by continuity testing and visual inspection
    
• Pilot Pump Failure or Blockage
  • No pilot pressure to actuate main valves
    
  • Requires pressure gauge and flow test
    
• Solenoid Coil Burnout or Sticking Valve
  

• Valve does not open despite signal
  
• Diagnosed by resistance check and manual activation
  

In one case, a contractor in Chile found that rodents had chewed through the wiring harness near the swing motor. After repairing the wires and resealing the harness, the machine regained full hydraulic function.
Repair Procedure and Component Recommendations
To restore full operation:

• Inspect and clean all ground points, especially near the battery and cab
  
• Test fuses and relays with a multimeter; replace any with irregular readings
  
• Check voltage at solenoid connectors with key on and engine running
  
• Use a pilot pressure gauge to confirm signal pressure at control valve
  
• Remove and clean solenoid valves; replace coils if resistance is outside spec
  
• Flush hydraulic fluid and replace filters if contamination is suspected
  

Recommended components:

• OEM solenoid valve kit for EX60 pilot circuit
  
• Wiring harness repair kit with waterproof connectors
  
• Pilot pressure test gauge with 0–500 psi range
  
• Replacement relays and fuses rated for EX60 electrical system
  
• High-quality hydraulic fluid with anti-foam additives
  

Preventive Maintenance and Long-Term Solutions
To avoid future failures:

• Inspect wiring harness quarterly for wear, corrosion, or rodent damage
  
• Clean and tighten ground connections during every service interval
  
• Replace hydraulic filters every 500 hours
  
• Monitor pilot pressure during operation and log readings
  
• Use dielectric grease on connectors to prevent moisture ingress
  
• Label fuse box and relay panel for faster troubleshooting
  

Some operators retrofit their EX60s with external diagnostic ports and LED indicators for solenoid status. Others install upgraded wiring harnesses with braided shielding for durability in harsh environments.
Real-World Anecdotes and Lessons Learned
A grading crew in Florida shared how their EX60 lost all hydraulic function during a storm cleanup. After hours of troubleshooting, they found a corroded fuse holder under the seat. Replacing the holder and sealing it with marine-grade epoxy restored the machine and prevented future failures.
In another case, a utility contractor in Japan installed a secondary battery ground strap after repeated electrical faults. Since then, their EX60 fleet has operated without a single monitor failure.
Recommendations for Fleet Managers and Technicians

• Maintain a diagnostic log with voltage readings, pressure tests, and fault codes
  
• Train operators to recognize early signs of electrical or hydraulic imbalance
  
• Stock spare solenoids, fuses, and wiring kits for field service
  
• Partner with Hitachi dealers for updated service bulletins and retrofit options
  
• Consider proactive harness replacement during major service intervals
  

For machines operating in high-duty cycles or wet terrain, consider sealed connectors and elevated wiring routes to reduce exposure.
Conclusion
When a Hitachi EX60 loses hydraulic and travel function, the solution lies in understanding the interplay between electrical signals and pilot pressure. With structured diagnostics and disciplined repair, technicians can restore full performance and extend the life of this compact workhorse. In the rhythm of excavation, control is everything—and when the circuits flow cleanly, the machine responds with precision.