Troubleshooting Slow Hydraulics in Hitachi EX120-2 Excavators

[MikePhua]

Hitachi's EX120-2 excavator is a powerful and reliable machine commonly used in construction, demolition, and heavy lifting tasks. However, like all heavy equipment, it can encounter problems over time. One of the most common issues that operators face is slow hydraulics. Hydraulic systems are essential for the proper functioning of excavators, controlling everything from the boom and arm to the bucket and swing functions. A malfunctioning hydraulic system can severely affect the performance of the entire machine.
This article explores the potential causes of slow hydraulic issues in the Hitachi EX120-2, along with diagnostic steps and solutions to get the machine back to optimal performance.
Common Causes of Slow Hydraulics in the Hitachi EX120-2
There are multiple reasons why the hydraulics on the Hitachi EX120-2 may slow down or fail to function at their usual capacity. Identifying the root cause can save time and money by preventing unnecessary repairs and replacements.

1. Low Hydraulic Fluid Levels
   Hydraulic systems rely on fluid to transmit pressure and power to various components. If the fluid levels are low, the system will struggle to generate the necessary pressure, resulting in slow or weak hydraulic operation.
   Solution:
   • Check the hydraulic fluid levels using the dipstick or sight gauge on the excavator.
     
   • If the fluid is below the recommended level, top it up with the correct type of fluid. Always ensure that the fluid meets the manufacturer’s specifications.
     
   • Regularly monitor fluid levels to prevent future low-fluid issues.
     
2. Contaminated Hydraulic Fluid
   Over time, hydraulic fluid can become contaminated with dirt, debris, or moisture, all of which can significantly affect the efficiency of the hydraulic system. Contaminants can cause blockages, excessive wear, and corrosion of components, leading to slow operation or complete system failure.
   Solution:
   • Inspect the hydraulic fluid for any signs of contamination, such as a dark or milky appearance.
     
   • If contamination is detected, perform a hydraulic fluid flush to remove impurities and replace the old fluid with fresh, clean fluid.
     
   • Replace or clean hydraulic filters to ensure optimal filtration and prevent future contamination.
     
3. Clogged Hydraulic Filters
   Hydraulic filters are designed to remove contaminants from the fluid, but over time, they can become clogged with debris. This blockage restricts the flow of hydraulic fluid, leading to slow operation or even system failure.
   Solution:
   • Inspect and replace hydraulic filters at regular intervals as recommended by the manufacturer.
     
   • Clean or replace filters immediately if slow hydraulics are suspected to be caused by clogged filters.
     
   • Ensure that only high-quality filters that match the equipment’s specifications are used.
     
4. Worn or Leaking Hydraulic Hoses and Connections
   Leaking or damaged hydraulic hoses and connections can lead to a loss of pressure in the system, resulting in sluggish hydraulic movement or total loss of function.
   Solution:
   • Inspect all hydraulic hoses and connections for visible signs of wear, cracks, or leaks.
     
   • Repair or replace any hoses that are leaking or damaged.
     
   • Ensure that all hydraulic fittings are properly tightened to prevent any loss of fluid or pressure.
     
5. Faulty Hydraulic Pump
   The hydraulic pump is responsible for pressurizing the fluid and sending it to various hydraulic components. A malfunctioning or worn-out pump can significantly reduce the performance of the hydraulic system, causing slow operation.
   Solution:
   • Test the hydraulic pump to ensure it is delivering the correct pressure.
     
   • If the pump is faulty, it may need to be repaired or replaced.
     
   • Regularly maintain the pump to avoid early failure and costly repairs.
     
6. Faulty Pressure Relief Valve
   The pressure relief valve in the hydraulic system controls the maximum pressure the system can produce. If this valve is malfunctioning or set incorrectly, it may prevent the system from reaching full pressure, causing the hydraulics to function slowly.
   Solution:
   • Check the pressure relief valve for correct settings and operation.
     
   • If the valve is malfunctioning, it may need to be cleaned, repaired, or replaced.
     
   • Consult the user manual for the appropriate pressure settings for your specific model.
     
7. Damaged Hydraulic Cylinders
   The hydraulic cylinders are responsible for converting hydraulic pressure into mechanical force, moving the boom, arm, and bucket. If these cylinders are damaged or the seals are worn, the machine may exhibit slow hydraulic response.
   Solution:
   • Inspect the hydraulic cylinders for any signs of wear, cracks, or leaks.
     
   • Replace any damaged cylinders or seals.
     
   • Ensure that cylinders are properly maintained and lubricated to prevent premature failure.
     

Diagnostic Steps to Identify the Root Cause
To effectively diagnose slow hydraulic issues in your Hitachi EX120-2, it’s essential to follow a systematic approach:

1. Start with Basic Checks: Begin by verifying the hydraulic fluid levels, checking for contamination, and inspecting the filters. These are the most common and easiest problems to identify.
   
2. Perform a Pressure Test: Use a hydraulic pressure gauge to measure the pressure in various parts of the system. This can help pinpoint whether the issue lies with the pump, relief valve, or other components.
   
3. Inspect for Leaks: Examine all hydraulic lines, hoses, and cylinders for any signs of leaks or damage. Even small leaks can lead to significant hydraulic issues.
   
4. Consult the Diagnostic Codes: If the machine is equipped with a diagnostic system, check for any error codes related to the hydraulic system. These codes can help identify specific components that are malfunctioning.
   

Preventive Maintenance for the Hitachi EX120-2
To avoid slow hydraulic issues in the future, consider these preventive maintenance practices:

• Regularly check fluid levels and change hydraulic fluid at the recommended intervals.
  
• Clean or replace filters regularly to maintain proper fluid flow and filtration.
  
• Inspect hydraulic hoses and connections for wear and tear, and replace them when necessary.
  
• Test the hydraulic system’s performance periodically to ensure that all components are working as expected.
  

Conclusion
Slow hydraulics in the Hitachi EX120-2 can be caused by a variety of issues, ranging from low fluid levels to damaged hydraulic pumps. Identifying the root cause through systematic diagnostic steps and addressing the problem promptly can restore the excavator’s hydraulic system to full functionality. Regular maintenance, such as fluid checks, filter replacements, and hose inspections, will help prevent future hydraulic issues and extend the life of your machine.
By staying proactive and following best maintenance practices, you can keep your Hitachi EX120-2 performing optimally, reducing downtime and ensuring that your equipment works efficiently when needed.