Hitachi EX450 LC-5 Hydraulic System Troubleshooting

[MikePhua]

The Hitachi EX450 LC-5 hydraulic excavator, renowned for its robust performance in heavy-duty applications, occasionally presents hydraulic system challenges. A prevalent issue involves the gradual decline in hydraulic power, particularly affecting the left-side travel functions, after the machine operates for approximately 5 to 15 minutes. This phenomenon is often attributed to the malfunctioning of the auxiliary pump, which, upon warming up, fails to maintain adequate pressure and flow, thereby compromising the performance of various hydraulic functions.
Understanding the Hydraulic System
The hydraulic system of the EX450 LC-5 is integral to its functionality, powering essential operations such as boom lifting, arm extension, bucket movement, and travel functions. The system comprises multiple components:

• Main Pumps: Responsible for generating hydraulic flow.
  
• Auxiliary Pumps: Supplemental pumps that provide additional hydraulic power to specific functions.
  
• Control Valves: Direct the flow of hydraulic fluid to various actuators.
  
• Hydraulic Cylinders: Convert hydraulic energy into mechanical force for movement.
  
• Hydraulic Motors: Drive rotational movements, such as the swing function.
  

In the case of the EX450 LC-5, the auxiliary pump, which powers the left-side travel and other functions, exhibits diminished performance after a short operational period.
Diagnostic Approach
A systematic diagnostic approach is essential to accurately identify the root cause of hydraulic issues:

1. Initial Observations: Operators report a noticeable reduction in the left-side travel speed after the machine has been running for 5 to 15 minutes.
   
2. Diagnostic Tool Utilization: Using the DR EX scan tool, no error codes are generated, suggesting the absence of electrical faults.
   
3. Sensor and Solenoid Evaluation: Monitoring the voltage signals from the swashplate and pressure sensors reveals no variation under load, indicating a potential mechanical failure within the pump.
   
4. Component Isolation: Swapping the pressure switch and solenoid harnesses between the inside and outside pumps does not alter the malfunction, further implicating the auxiliary pump.
   

Potential Causes
Several factors may contribute to the observed hydraulic issues:

• Pump Wear and Tear: Over time, components within the auxiliary pump can experience wear, leading to reduced efficiency and failure to maintain adequate pressure and flow.
  
• Internal Contamination: Debris or contaminants within the hydraulic fluid can cause blockages or damage to pump components, impairing functionality.
  
• Seal Degradation: Worn or damaged seals can lead to internal leaks, resulting in pressure loss and diminished performance.
  
• Improper Calibration: Incorrect calibration of the pump's swashplate angle can affect its ability to adjust displacement, leading to inadequate hydraulic output.
  

Repair and Maintenance Recommendations
To address and rectify hydraulic system issues:

1. Pump Inspection and Replacement: Thoroughly inspect the auxiliary pump for signs of wear or damage. If necessary, replace the pump with a new or rebuilt unit to restore full hydraulic capacity.
   
2. System Flushing: Flush the hydraulic system to remove any contaminants that may have accumulated, preventing further damage to components.
   
3. Seal Replacement: Replace any degraded seals to prevent internal leaks and ensure optimal pressure retention.
   
4. Calibration Verification: Verify and, if needed, recalibrate the pump's swashplate angle to ensure proper displacement adjustment under varying load conditions.
   
5. Regular Maintenance: Implement a routine maintenance schedule that includes regular inspections, fluid changes, and component checks to prolong the lifespan of the hydraulic system.
   

Conclusion
The hydraulic issues observed in the Hitachi EX450 LC-5, particularly concerning the auxiliary pump's performance, underscore the importance of regular maintenance and prompt attention to emerging problems. By adhering to recommended diagnostic procedures and maintenance practices, operators can mitigate the risk of hydraulic failures and ensure the continued reliability and efficiency of the excavator.