Hitachi EX120 Drive Motor Issues and Solutions

[MikePhua]

The Hitachi EX120 is a popular excavator in the 12-ton class, known for its performance and durability in various heavy-duty applications. However, like all machinery, it can experience wear and tear, and issues related to its drive motor are not uncommon. The drive motor is a crucial component in the hydraulic system of an excavator, responsible for powering the tracks and enabling mobility. When it malfunctions, it can significantly affect the machine’s performance and even cause complete operational failure if not addressed promptly.
This article will delve into the common issues related to the Hitachi EX120 drive motor, how to diagnose these problems, potential solutions, and tips for maintaining the drive motor to avoid costly repairs.
Understanding the Role of the Drive Motor in Excavators
The drive motor in an excavator, including the Hitachi EX120, is part of the hydraulic system that powers the tracks. It converts hydraulic pressure into mechanical power, allowing the tracks to move forward or backward. The drive motor is connected to the final drive system, which includes components like gears, bearings, and the track sprockets, all of which work in unison to provide smooth movement.
The hydraulic system uses oil under high pressure to actuate various components of the excavator, and the drive motor is responsible for translating this hydraulic force into rotational movement of the wheels or tracks. If the drive motor is not functioning properly, it can lead to sluggish movement, reduced power, or even complete immobilization of the machine.
Common Issues with the Hitachi EX120 Drive Motor
Several issues can arise with the drive motor in a Hitachi EX120 excavator. Some of the most common problems include:

1. Loss of Power or Sluggish Movement
   • Symptoms: The excavator moves slowly or feels underpowered, especially when attempting to move heavy loads.
     
   • Possible Causes: This could be due to low hydraulic pressure, a failing drive motor, clogged filters, or issues with the hydraulic pump.
     
   • Solution: Begin by checking the hydraulic fluid level and pressure. If the fluid is low or the pressure is inadequate, top up the hydraulic system and test again. Inspect the drive motor for signs of wear or damage, and if necessary, clean or replace filters and check for leaks in the hydraulic lines.
     
2. No Movement
   • Symptoms: The excavator fails to move, even when attempting to operate the controls.
     
   • Possible Causes: A complete failure of the drive motor, damage to the hydraulic lines, or issues with the final drive assembly could be to blame.
     
   • Solution: If no movement occurs, inspect the hydraulic lines for blockages or leaks. Check the drive motor for physical damage or wear. It may require a full overhaul or replacement if it has failed completely.
     
3. Strange Noises
   • Symptoms: Unusual whining, grinding, or screeching sounds coming from the drive motor or hydraulic system.
     
   • Possible Causes: Air in the hydraulic lines, low fluid levels, or internal damage to the drive motor or associated components.
     
   • Solution: First, check for air in the hydraulic lines. If the system is low on fluid, top it up. If the noise persists, it could indicate damage to the drive motor or the hydraulic pump, in which case further inspection or replacement is necessary.
     
4. Excessive Heat in the Hydraulic System
   • Symptoms: Overheating of the hydraulic system, which may cause the machine to shut down or go into a “limp mode.”
     
   • Possible Causes: This could be the result of a malfunctioning drive motor, clogged filters, or inadequate hydraulic fluid.
     
   • Solution: Check for clogged filters, and ensure that the hydraulic fluid is at the correct level and is in good condition. If the issue is caused by a failing drive motor, it may need to be replaced or repaired.
     
5. Leaks Around the Drive Motor
   • Symptoms: Visible oil leaks around the drive motor or hydraulic lines.
     
   • Possible Causes: Worn seals, damaged hoses, or a cracked motor casing.
     
   • Solution: Inspect the seals and hoses around the drive motor for damage or wear. Replace any damaged parts and ensure that the motor housing is intact. Leaks should be addressed immediately, as they can lead to loss of hydraulic fluid and potential damage to other components.
     

Diagnosing Drive Motor Problems
When diagnosing issues with the Hitachi EX120 drive motor, a methodical approach is necessary to ensure the right problem is identified. Here’s a step-by-step guide to troubleshooting:

1. Check Hydraulic Fluid: Low or dirty hydraulic fluid is often the root cause of many drive motor problems. Inspect the fluid level and condition regularly. If the fluid appears milky or contaminated, it may need to be replaced.
   
2. Measure Hydraulic Pressure: Using a pressure gauge, check the hydraulic pressure at the drive motor. Low pressure may indicate a failing pump or issues in the hydraulic circuit, which could affect the motor’s performance.
   
3. Inspect Filters and Lines: Clogged filters and damaged hydraulic lines can restrict fluid flow to the drive motor, causing performance issues. Replace filters as part of regular maintenance and check hydraulic lines for leaks or blockages.
   
4. Listen for Unusual Noises: Strange noises coming from the drive motor or hydraulic system are often a sign of internal damage or cavitation. If you hear a whining sound, it could indicate low fluid or air in the system. Grinding or rattling sounds suggest that the motor may be internally damaged.
   
5. Perform a Pressure Test on the Drive Motor: A more advanced method involves performing a load test on the drive motor. This test can help identify if the motor is producing sufficient power or if there is excessive wear within the motor components.
   

Preventing Drive Motor Problems
Proper maintenance is essential for ensuring the longevity and reliability of the Hitachi EX120 drive motor. Here are some proactive measures to help prevent common issues:

1. Regular Hydraulic System Maintenance: Change the hydraulic fluid and filters at regular intervals, as recommended in the owner’s manual. Ensure that the hydraulic oil is clean and free from contaminants.
   
2. Monitor Fluid Levels and Pressure: Always monitor the hydraulic fluid levels and pressure. Low levels or insufficient pressure can lead to poor motor performance or even failure.
   
3. Inspect the Drive Motor: Periodically inspect the drive motor for signs of external damage, leaks, or excessive wear. Catching issues early can prevent the need for expensive repairs later.
   
4. Proper Use and Operation: Avoid overloading the machine, as this can strain the drive motor and hydraulic system. Ensure that operators are properly trained and follow the recommended operating procedures.
   

When to Replace the Drive Motor
If the drive motor on a Hitachi EX120 is significantly damaged, repairs may not be feasible, and replacement becomes the only option. Some signs that the drive motor may need to be replaced include:

• Persistent performance issues despite troubleshooting.
  
• Severe internal damage or wear that cannot be repaired.
  
• Leaking that cannot be sealed or fixed with replacement seals.
  

In these cases, sourcing a high-quality replacement motor from an authorized dealer or trusted aftermarket supplier is essential to restore the machine’s performance.
Conclusion
The drive motor in a Hitachi EX120 is a vital component that ensures the machine's mobility and operational efficiency. While it is designed to be durable, regular maintenance and prompt attention to issues like fluid levels, pressure, and leaks are crucial to preventing costly repairs. By understanding the common problems associated with the drive motor and following a systematic approach to diagnosis and maintenance, operators can keep their machines running smoothly, minimizing downtime and extending the lifespan of their equipment.