Hitachi EX160LC-5 Hydraulic Lag and Engine Load Troubleshooting

[MikePhua]

The EX160LC-5 and Hitachi’s Mid-Size Excavator Lineage
The Hitachi EX160LC-5 is part of the Dash-5 series, a generation of excavators known for mechanical simplicity and robust hydraulic performance. Built for general excavation, trenching, and utility work, the EX160LC-5 features an Isuzu diesel engine paired with a load-sensing hydraulic system. With an operating weight around 17,000 kg and a dig depth exceeding 6 meters, it occupies a versatile niche between compact and full-size machines.
Hitachi, founded in 1910 and headquartered in Tokyo, has long emphasized hydraulic refinement and fuel efficiency. The EX160LC-5 was designed to deliver consistent performance with minimal electronic complexity, making it a favorite among owner-operators and rural contractors.
Symptoms of Hydraulic and Engine Performance Loss
Operators encountering performance issues with the EX160LC-5 often report:

• Engine bogging or choking under load
  
• Sluggish boom and arm movement
  
• Travel motors starting slow then surging
  
• No noticeable difference between HP and economy modes
  
• Hydraulic functions lacking force or speed
  

These symptoms suggest a systemic imbalance between engine output and hydraulic demand. In most cases, the engine is not the root cause—it is reacting to excessive load from the hydraulic system, often due to internal restriction or control valve malfunction.
A contractor in Alberta noted that his EX160LC-5 would stall during digging, even in HP mode. After checking boost pressure and pilot pressure, he discovered that the main control valve had a broken spring in one of the spool chambers, causing erratic flow and excessive engine load.
Turbocharger and Boost Pressure Evaluation
The EX160LC-5’s Isuzu engine is turbocharged, and boost pressure plays a critical role in maintaining torque under hydraulic load. If the turbo fails to spool properly, the engine may choke when hydraulic demand spikes.
Recommended test procedure:

• Warm engine and hydraulic system to operating temperature
  
• Stall the arm function in HP mode while monitoring boost
  
• Target boost pressure: approx. 8.5 psi at 2150 rpm
  
• Feather the arm several times to capture peak boost
  

If boost is low, inspect:

• Turbocharger for shaft play or carbon buildup
  
• Wastegate actuator and linkage
  
• Intake piping for leaks or collapsed hoses
  
• Air filter condition and restriction indicator
  

In Texas, a fleet manager replaced a turbo after discovering that the wastegate was stuck partially open. After the repair, engine response improved and hydraulic functions regained full speed.
Hydraulic System and Control Valve Behavior
The EX160LC-5 uses a variable displacement piston pump controlled by pilot pressure and load-sensing feedback. If the control valve malfunctions, the pump may overcompensate, dragging the engine down.
Key inspection points:

• Pilot pressure: should be stable around 38 kg/cm²
  
• Proportional solenoid valve: clean and responsive
  
• Signal box pressure lines: test with gauge and isolate if needed
  
• Control valve spools: check for spring failure or sticking
  

A technician in New Zealand found that a broken spring inside the main control valve caused one spool to remain partially open, creating constant backpressure. After replacing the spring and resealing the valve block, the machine returned to normal operation.
Electrical and Sensor Integrity
While the EX160LC-5 is not heavily electronic, sensor faults can still affect performance:

• HP mode switch: verify continuity and ECM response
  
• Throttle position sensor: check for smooth voltage sweep
  
• Pressure sensors: test for accuracy and signal stability
  
• Wiring harness: inspect for corrosion or loose connectors
  

If HP mode has no effect, the ECM may be ignoring the input due to a failed switch or broken wire. A contractor in Oregon discovered that a rodent had chewed through the HP mode wire under the cab. After repairing the harness, the machine regained full responsiveness.
Fuel System and Engine Load Isolation
To rule out fuel-related engine choking:

• Replace fuel filters and inspect for contamination
  
• Check lift pump output and fuel pressure at injection pump
  
• Inspect return line for restriction
  
• Test engine oil for signs of fuel dilution
  

If the engine stalls even with hydraulics disabled, the issue may lie in the fuel system or internal engine wear. However, most cases of choking under hydraulic load point to pump or valve dysfunction.
In Alaska, a forestry crew replaced the fuel lift pump after noticing intermittent stalling. The pump had degraded internally, starving the injection pump under load. After replacement, engine stability improved.
Preventive Measures and Long-Term Reliability
To maintain optimal performance:

• Change hydraulic filters every 500 hours
  
• Inspect turbo and intake system quarterly
  
• Test pilot pressure during annual service
  
• Clean solenoid valves and control spools regularly
  
• Monitor fuel quality and replace filters proactively
  

A contractor in Thailand implemented a monthly hydraulic pressure check and reduced engine load complaints by 80%. His team now logs pilot pressure and boost readings during routine service.
Stories from the Field
In Finland, an EX160LC-5 used for canal dredging began choking during swing operations. The issue was traced to a clogged pilot filter restricting control signal flow. After replacing the filter and flushing the pilot lines, the machine regained full hydraulic speed.
In Oregon, a machine showed no difference between HP and economy modes. The technician discovered that the HP mode wire had been disconnected during a previous repair. After restoring the connection, the machine’s digging force increased noticeably.
Conclusion
Slow hydraulics and engine choking in the Hitachi EX160LC-5 are often linked to control valve irregularities, pilot pressure instability, or turbocharger underperformance. By methodically testing boost, pilot pressure, and valve behavior, operators can isolate the root cause and restore full machine capability. In a system where engine and hydraulics must work in harmony, even a small fault can ripple into major productivity loss—making precision diagnostics the key to uptime.