Hitachi EX120-2 Hydraulic Excavator: Performance and Troubleshooting

[MikePhua]

Introduction
The Hitachi EX120-2 is a hydraulic crawler excavator that gained popularity in the 1990s for its robust performance and reliability in various construction and excavation tasks. Manufactured by Hitachi Construction Machinery, this model was designed to offer versatility and efficiency, making it a preferred choice for contractors and operators worldwide.
Specifications

• Engine: Isuzu 4BD1T turbocharged diesel engine
  
• Engine Power: Approximately 80–85 horsepower
  
• Operating Weight: Approximately 11,800 kg (26,000 lbs)
  
• Bucket Capacity: 0.45 m³
  
• Dimensions:
  • Overall Length: 7,580 mm
    
  • Overall Width: 2,500 mm
    
  • Overall Height: 2,700 mm
    
  • Track Length: 3,580 mm
    
  • Track Gauge: 1,990 mm
    
  • Ground Clearance: 1,450 mm
    
• Hydraulic System: Closed-center load sensing system with variable displacement pump
  

Performance and Features
The EX120-2 was equipped with Hitachi's advanced hydraulic system, providing smooth and responsive control for various attachments and operations. Its compact size and powerful engine allowed for efficient work in confined spaces, making it suitable for urban construction projects. The machine's durability and ease of maintenance contributed to its popularity among operators.
Common Issues and Troubleshooting
Despite its reliability, the EX120-2 has experienced certain issues over time. Operators have reported:

• Hydraulic Slowdown After Warm-Up: Some users have noted a decrease in hydraulic performance after the machine warms up. This could be due to issues like a blown fuse affecting the hydraulic controls or problems with the hydraulic pump.
  
• Hydraulic Functions Becoming Slow: In some cases, the swing and travel functions become extremely slow. This could be related to solenoid issues on top of the pump or problems with the variable pressure compensator valve in the pilot system.
  
• Electrical and Sensor Problems: Issues with the throttle stepping motor, wiring harness, or sensors can lead to starting difficulties or erratic engine behavior.
  

Maintenance Tips
To ensure optimal performance and longevity of the EX120-2:

• Regularly Check Hydraulic Fluid Levels: Maintain proper fluid levels and replace the fluid as recommended by the manufacturer.
  
• Inspect and Clean Filters: Regularly check and clean air and fuel filters to prevent clogging and ensure efficient engine performance.
  
• Monitor Electrical Components: Inspect wiring and connectors for signs of wear or corrosion, and replace faulty components promptly.
  
• Calibrate Sensors and Controls: Ensure that sensors and control systems are properly calibrated to maintain accurate operation.
  

Conclusion
The Hitachi EX120-2 remains a testament to Hitachi's commitment to quality and innovation in construction machinery. While it has encountered some challenges over the years, regular maintenance and timely troubleshooting can address most issues, allowing operators to continue benefiting from its capabilities. As with any heavy equipment, staying proactive in maintenance and being attentive to potential problems will ensure the EX120-2 continues to serve effectively in various applications.