Troubleshooting Slow and Weak Hydraulics in the Hitachi EX120-2 Excavator

[MikePhua]

The Hitachi EX120-2 is a widely used hydraulic excavator, known for its reliability and efficiency in various digging and lifting operations. However, like many heavy equipment machines, it can occasionally experience performance issues, particularly with its hydraulic system. One common issue faced by operators is slow and weak hydraulics, which can significantly impact the machine’s overall functionality. In this article, we will explore the possible causes of slow and weak hydraulics in the Hitachi EX120-2, provide troubleshooting steps, and discuss potential solutions to restore optimal performance.
Understanding the Hydraulic System in the Hitachi EX120-2
The hydraulic system in the Hitachi EX120-2 is central to its operation. It powers critical functions such as the boom, arm, bucket, and swivel motors. The hydraulic system relies on high-pressure fluid to provide the necessary force to carry out various tasks. A typical hydraulic system in an excavator includes:

• Hydraulic Pump: The pump is responsible for generating the hydraulic pressure required for the system to function.
  
• Hydraulic Fluid: The fluid used in the system to transmit force, lubricate components, and prevent wear.
  
• Hydraulic Cylinders: These are the actuators that use hydraulic pressure to provide the motion needed for digging, lifting, and moving.
  
• Control Valves: These valves regulate the flow of hydraulic fluid to different parts of the excavator, ensuring precise control over its functions.
  

A malfunction in any of these components can result in a drop in hydraulic pressure, leading to weak or slow movement in the machine’s operations.
Common Causes of Slow and Weak Hydraulics
When experiencing slow or weak hydraulics in the Hitachi EX120-2, several factors could be at play. Here are some of the most common causes of this issue:
1. Low Hydraulic Fluid Level
One of the simplest and most common causes of slow hydraulics is insufficient hydraulic fluid. If the fluid level drops below the recommended level, the hydraulic pump may not be able to generate the required pressure, leading to weak performance in the hydraulic system.

• Symptoms: Slow arm, boom, or bucket movements, along with potential overheating of the hydraulic system.
  
• Solution: Check the hydraulic fluid levels regularly and top up as necessary using the correct type of fluid recommended by the manufacturer.
  

2. Contaminated Hydraulic Fluid
Over time, hydraulic fluid can become contaminated with dirt, debris, or moisture. Contaminated fluid can cause clogs in the system, reducing efficiency and leading to slow hydraulics. Dirt and debris can wear out the internal components of the pump and valves, while moisture can cause rust and corrosion.

• Symptoms: Uneven movement or sluggish operation of the hydraulic components, strange noises, or discolored fluid.
  
• Solution: Drain the contaminated fluid and replace it with fresh, clean hydraulic fluid. It’s also essential to clean the system’s filters and replace any worn-out seals or gaskets.
  

3. Faulty Hydraulic Pump
The hydraulic pump is the heart of the system, and if it starts to fail, the entire system can experience slow or weak hydraulics. Issues such as worn-out gears, damaged components, or air contamination can result in a drop in the pump's ability to generate pressure.

• Symptoms: Slow or erratic movements, especially under load, or a noticeable drop in lifting power.
  
• Solution: Inspect the pump for signs of wear, leaks, or damage. If the pump is found to be faulty, it may need to be repaired or replaced.
  

4. Leaking Hydraulic Hoses or Fittings
Hydraulic hoses and fittings are responsible for carrying pressurized fluid throughout the system. If there are any leaks in these components, hydraulic fluid will escape, reducing the overall pressure in the system. Leaks can occur due to wear and tear, corrosion, or physical damage to the hoses or fittings.

• Symptoms: Noticeable fluid loss around hoses, fittings, or cylinders, along with weak or slow hydraulic performance.
  
• Solution: Inspect all hydraulic hoses and fittings for signs of damage or leaks. Replace any damaged hoses or fittings, and ensure that all connections are properly tightened.
  

5. Clogged Hydraulic Filters
Hydraulic filters are designed to remove contaminants from the fluid as it circulates through the system. If the filters become clogged or dirty, they can restrict the flow of fluid, leading to slow and inefficient hydraulics.

• Symptoms: Gradual loss of hydraulic power, with the system becoming slower over time, especially after extended use.
  
• Solution: Replace the hydraulic filters regularly, as per the manufacturer’s recommendations. If filters are clogged, they can be cleaned or replaced to restore fluid flow and pressure.
  

6. Malfunctioning Control Valve
The control valve regulates the flow of hydraulic fluid to various components like the boom, arm, and bucket. If the control valve is malfunctioning, it may not direct enough fluid to the actuators, resulting in weak or slow movements.

• Symptoms: Inconsistent or jerky movements, unresponsive controls, or a lack of power when trying to perform tasks like digging or lifting.
  
• Solution: Inspect the control valve for blockages or signs of wear. Clean or replace the valve if necessary.
  

7. Air in the Hydraulic System
Air trapped within the hydraulic system can cause a drop in hydraulic pressure, leading to weak performance. Air can enter the system through leaks in the hoses or fittings, or during the process of topping up the hydraulic fluid.

• Symptoms: Irregular or jerky movement, along with a soft or unresponsive feeling when operating the controls.
  
• Solution: Bleed the hydraulic system to remove trapped air. This is done by releasing air from the hydraulic lines through the designated bleed valves.
  

Troubleshooting the Issue
To troubleshoot and fix slow or weak hydraulics, operators should follow a step-by-step approach:

1. Check the Hydraulic Fluid Level
   • Ensure that the fluid level is within the recommended range. If it’s low, top up with the appropriate hydraulic fluid.
     
   • Examine the fluid’s condition for any signs of contamination or discolouration.
     
2. Inspect for Leaks and Hoses Damage
   • Inspect all hydraulic hoses, fittings, and cylinders for leaks or damage.
     
   • Tighten any loose connections and replace damaged hoses or seals.
     
3. Change the Hydraulic Fluid and Filters
   • If the fluid is contaminated, drain it and replace it with fresh, clean fluid. Don’t forget to replace the hydraulic filters to ensure the system runs smoothly.
     
4. Examine the Hydraulic Pump
   • Inspect the hydraulic pump for wear or damage. If the pump is malfunctioning, repair or replace it to restore proper pressure generation.
     
5. Check the Control Valve and Clean It
   • Inspect the control valve for blockages or damage. Clean or replace it if necessary to ensure fluid is directed properly to the actuators.
     
6. Bleed the System
   • If air has entered the system, bleed the hydraulic lines to remove it. This will help restore the system’s pressure.
     

Preventive Maintenance Tips
To prevent issues with slow or weak hydraulics in the future, consider the following preventive maintenance tips:

• Regular Fluid and Filter Changes: Regularly check and replace hydraulic fluid and filters to ensure the system runs efficiently.
  
• Leak Inspections: Periodically inspect hoses and fittings for leaks or damage, as they can lead to significant loss of hydraulic pressure.
  
• System Bleeding: Make it a habit to bleed the hydraulic system when topping up fluid to prevent air from entering the system.
  
• Pump Maintenance: Keep the hydraulic pump in good condition by checking for wear or damage regularly.
  

Conclusion
Slow and weak hydraulics in the Hitachi EX120-2 can stem from several issues, including low fluid levels, contamination, leaking hoses, and faulty components. By systematically troubleshooting the problem and replacing or repairing the faulty parts, operators can restore the excavator's hydraulic system to optimal performance. Regular maintenance, such as fluid checks, filter replacements, and inspections, is key to preventing future hydraulic problems and ensuring the machine continues to perform at its best.