Hydraulic Pump Troubleshooting for Hitachi UH122 Excavators: A Comprehensive Guide

[MikePhua]

Introduction
The Hitachi UH122 excavator, a robust machine renowned for its performance in various construction and excavation tasks, relies heavily on its hydraulic system to execute functions such as lifting, digging, and swinging. Central to this system is the hydraulic pump, which generates the necessary pressure to power these operations. Over time, issues may arise within the hydraulic pump, leading to decreased performance and potential system failures. This guide delves into common hydraulic pump problems in the UH122, diagnostic methods, and effective solutions to restore optimal functionality.
Understanding the Hydraulic System of the UH122
The hydraulic system of the Hitachi UH122 is designed to provide efficient power transmission to various machine functions. Key components include:

• Hydraulic Pump: Responsible for converting mechanical energy from the engine into hydraulic energy, generating the pressure required for system operations.
  
• Hydraulic Fluid: Transports energy within the system, lubricates components, and helps dissipate heat.
  
• Hydraulic Cylinders and Motors: Execute the mechanical movements necessary for tasks like lifting, digging, and swinging.
  
• Control Valves: Direct the flow of hydraulic fluid to specific components, enabling precise control over movements.
  

A malfunction in any of these components can lead to hydraulic issues, affecting the overall performance of the excavator.
Common Hydraulic Pump Issues in the UH122

1. Loss of Hydraulic Power
   A noticeable decrease in lifting capacity or sluggish movement of the boom and arm can indicate a problem with the hydraulic pump. Possible causes include:
   • Worn Pump Components: Over time, internal parts such as pistons and valves can wear out, leading to reduced efficiency.
     
   • Contaminated Hydraulic Fluid: Dirt, water, or metal particles in the fluid can cause internal damage to the pump.
     
   • Air in the Hydraulic System: Entrained air can compress, leading to erratic pump performance and cavitation.
     
2. Hydraulic Fluid Leaks
   Leaks can occur at various points in the hydraulic system, including the pump seals and hoses. These leaks can lead to a drop in fluid levels, causing overheating and potential damage to components.
   
3. Unusual Noises
   Grinding, whining, or knocking sounds emanating from the hydraulic pump can indicate cavitation, air entrainment, or internal damage.
   

Diagnostic Procedures
To accurately diagnose hydraulic pump issues in the UH122:

1. Inspect Hydraulic Fluid
   • Check Fluid Level: Ensure the hydraulic fluid is at the recommended level.
     
   • Assess Fluid Condition: Examine the fluid for signs of contamination, such as discoloration or particulates.
     
   • Replace Contaminated Fluid: If the fluid appears contaminated, drain and replace it with the specified type and grade.
     
2. Examine for Leaks
   • Inspect Seals and Hoses: Look for visible signs of leakage around the pump and associated components.
     
   • Pressurize System: With the engine running, use a pressure gauge to identify any drop in system pressure, which may indicate internal leaks.
     
3. Listen for Unusual Noises
   • Operate the Excavator: Run the machine through various functions and listen for any abnormal sounds.
     
   • Note Specific Conditions: Determine if the noises occur under specific loads or speeds, which can help pinpoint the issue.
     

Potential Solutions

1. Pump Repair or Replacement
   • Repair: If the pump components are worn but not severely damaged, a professional repair service can refurbish the pump to restore its functionality.
     
   • Replacement: In cases of extensive damage, replacing the pump with a new or refurbished unit may be necessary.
     
2. Hydraulic Fluid Maintenance
   • Regular Flushing: Implement a routine to flush the hydraulic system to remove contaminants.
     
   • Use of Quality Filters: Install high-quality filters to prevent debris from entering the system.
     
3. Seal and Hose Replacement
   • Use OEM Parts: Replace worn seals and hoses with original equipment manufacturer (OEM) parts to ensure compatibility and reliability.
     
4. System Bleeding
   • Remove Air Entrapment: Bleed the hydraulic system to eliminate any trapped air, restoring normal operation.
     

Preventive Maintenance Tips
To prolong the life of the hydraulic system and prevent future issues:

• Regular Fluid Checks: Monitor hydraulic fluid levels and condition regularly.
  
• Scheduled Maintenance: Follow the manufacturer's recommended maintenance schedule for the UH122.
  
• Operator Training: Ensure operators are trained to recognize early signs of hydraulic issues and understand proper machine operation.
  

Conclusion
The hydraulic pump is a critical component of the Hitachi UH122 excavator's performance. Understanding common issues, diagnostic procedures, and maintenance practices can help operators and technicians effectively manage hydraulic system health. By implementing proactive maintenance and addressing problems promptly, the longevity and reliability of the UH122 can be significantly enhanced.