The Hitachi EX120-3 Excavator: Comprehensive Guide to Performance, Maintenance and Optimization

[MikePhua]

Introduction to a Legendary Workhorse
The Hitachi EX120-3 represents one of the most reliable mid-sized excavators ever produced, with many units still operating at peak performance decades after manufacture. This 12-ton class machine became famous for its bulletproof Isuzu engine and innovative hydraulic system that set new standards in the 1990s construction equipment market.
Key Specifications and Design Features
Powerplant Performance

• Isuzu AL-4LE2X diesel engine
  
• 92 HP (69 kW) at 2,000 rpm
  
• 4-cylinder, liquid-cooled design
  
• Mechanical fuel injection system
  

Hydraulic System Capabilities

• Main pump output: 2 x 54 L/min
  
• System pressure: 34.3 MPa (4,976 psi)
  
• Independent travel motors
  
• Auto-deceleration system
  

Operating Characteristics

• Weight: 12,200-12,800 kg (depending on configuration)
  
• Max digging depth: 4,570 mm
  
• Bucket capacity: 0.28-0.52 m³
  

Common Operational Issues and Solutions
1. Hydraulic System Concerns
Frequent Problems:

• Slow cylinder response
  
• Drifting boom
  
• Weak digging power
  

Diagnostic Approach:

• Check pump pressure (should maintain 4,900-5,000 psi)
  
• Test control valve operation
  
• Inspect cylinder seals for internal leakage
  

2. Undercarriage Maintenance
Critical Wear Points:

• Track chain stretch (replace at 3% elongation)
  
• Sprocket tooth wear (check for hooking pattern)
  
• Roller flange wear
  

Maintenance Tips:

• Clean undercarriage daily
  
• Maintain proper track tension (25-30mm sag)
  
• Rotate track links annually
  

3. Engine Performance Issues
Typical Symptoms:

• Hard starting
  
• Excessive smoke
  
• Power loss
  

Troubleshooting Steps:

1. Compression test (should be 350-400 psi)
   
2. Check injection timing
   
3. Inspect air filter restriction indicator
   

Preventive Maintenance Schedule
Daily Checks

• Engine oil level
  
• Coolant level
  
• Hydraulic fluid condition
  
• Track tension
  

Every 250 Hours

• Replace all filters (fuel, oil, air)
  
• Grease all fittings (use molybdenum disulfide grease)
  
• Check valve clearances
  

Every 1,000 Hours

• Change hydraulic fluid
  
• Inspect swing bearing
  
• Test alternator output
  

Performance Enhancement Options
1. Hydraulic System Upgrades

• High-efficiency main pump ($2,500-3,800)
  
• Precision control valves ($1,200-1,800)
  
• Auxiliary hydraulic circuit addition
  

2. Operator Comfort Improvements

• Air suspension seat conversion
  
• LED lighting kit
  
• Climate control cab (retrofit option)
  

3. Technology Add-ons

• GPS grade control system
  
• Fuel monitoring device
  
• Remote diagnostics module
  

Case Study: Forestry Application Success
A Canadian logging company operates six EX120-3 excavators with these modifications:

• Reinforced undercarriages
  
• Forestry protection packages
  
• High-flow hydraulics for processing heads
  

Result: Average 8,500 hours between major overhauls - 20% better than industry standard for this class.
Cost of Ownership Analysis
5-Year Projection (1,500 hrs/year)

• Fuel: $28,000
  
• Routine maintenance: $9,500
  
• Major repairs: $12,000
  
• Resale value retention: 55-60%
  

Comparison to Modern Equivalents
While newer excavators offer 10-15% better fuel efficiency, the EX120-3's lower depreciation and repair costs often make it more economical for small contractors.
Troubleshooting Guide for Common Problems
Problem: Excessive Hydraulic Oil Heating
Possible Causes:

• Clogged oil cooler
  
• Worn pump components
  
• Incorrect viscosity oil
  

Solutions:

• Clean cooler fins
  
• Test pump efficiency
  
• Switch to ISO 46 hydraulic oil
  

Problem: Electrical Gremlins
Troubleshooting Steps:

1. Check battery connections
   
2. Test alternator output (should be 28V)
   
3. Inspect fuse panel for corrosion
   

Operator Tips for Maximum Efficiency

• Use auto-deceleration feature properly
  
• Match engine speed to hydraulic demand
  
• Avoid excessive idling
  
• Practice smooth control movements
  

Parts Availability and Support
While some OEM parts are discontinued, quality alternatives exist:

• Aftermarket undercarriage components
  
• Rebuilt hydraulic pumps
  
• Engine overhaul kits
  

Final Verdict
The EX120-3 remains one of the best values in used excavators today. As one equipment manager noted: "We've got three EX120-3s with over 15,000 hours each - they just keep going with basic care." For operators needing a dependable, economical machine that can handle tough jobs, this Hitachi model continues to deliver exceptional value decades after its introduction.
Pro Tip: When purchasing a used EX120-3, prioritize units with documented service history over low-hour machines with unknown maintenance background. Proper care matters far more than simple age or hour meter readings for these durable excavators.