Hydraulic System Overpressure in Takeuchi TB135: Causes and Solutions

[MikePhua]

Introduction
The Takeuchi TB135 mini-excavator, introduced in 1999, is a robust machine known for its performance and reliability. However, like all machinery, it can experience issues over time. One such problem reported by operators is hydraulic system overpressure, leading to engine bogging and even hydraulic tank bulging. Understanding the causes and implementing effective solutions is crucial for maintaining the machine's performance.
Understanding Hydraulic System Overpressure
Hydraulic systems in excavators operate under high pressure to perform tasks efficiently. However, if the system experiences excessive pressure, it can lead to various issues:

• Engine Bogging: Excessive pressure can cause the engine to work harder, leading to a decrease in power and potential stalling.
  
• Hydraulic Tank Bulging: Overpressure can cause the hydraulic tank to expand or bulge, indicating internal pressure buildup.
  

Common Causes of Hydraulic Overpressure
Several factors can contribute to hydraulic system overpressure:

1. Faulty Pressure Relief Valve: The pressure relief valve regulates the system's pressure. If it malfunctions or becomes stuck, it can fail to release excess pressure, leading to overpressure situations.
   
2. Clogged Hydraulic Filters: Filters prevent contaminants from entering the hydraulic system. Over time, they can become clogged, restricting fluid flow and causing pressure buildup.
   
3. Air in the Hydraulic System: Air pockets can form in the hydraulic system, leading to erratic operation and pressure fluctuations.
   
4. Overfilled Hydraulic Fluid: Excess hydraulic fluid can cause the system to operate under higher pressure, leading to overpressure situations.
   
5. Malfunctioning Hydraulic Pump: A failing pump can produce excessive pressure, overwhelming the system.
   

Case Study: TB135 Hydraulic System Overpressure
An operator reported experiencing engine bogging and a bulging hydraulic tank while using the Takeuchi TB135. The issues began after replacing the travel motors and final drives, as well as draining and replacing the hydraulic fluid and filter. Despite these maintenance efforts, the power continued to decrease over time.
The operator's experience highlights the importance of addressing potential overpressure issues in the hydraulic system. A bulging hydraulic tank is a clear indication of internal pressure buildup, which can lead to severe damage if not addressed promptly.
Troubleshooting and Solutions
To address hydraulic system overpressure in the TB135, consider the following steps:

1. Inspect and Replace the Pressure Relief Valve: Ensure the pressure relief valve is functioning correctly. Replace it if necessary to maintain proper system pressure.
   
2. Clean or Replace Hydraulic Filters: Regularly check and replace hydraulic filters to ensure unobstructed fluid flow.
   
3. Bleed Air from the Hydraulic System: Follow the manufacturer's guidelines to remove air pockets from the system, ensuring smooth operation.
   
4. Check Hydraulic Fluid Levels: Ensure the hydraulic fluid is at the recommended level. Overfilling can lead to overpressure situations.
   
5. Inspect the Hydraulic Pump: Check the hydraulic pump for signs of wear or malfunction. Replace it if necessary to prevent excessive pressure buildup.
   

Preventive Maintenance Tips
To prevent future hydraulic system overpressure issues:

• Regularly Inspect Hydraulic Components: Routine checks can help identify potential issues before they become major problems.
  
• Follow Manufacturer's Maintenance Schedule: Adhering to the recommended maintenance schedule ensures all components function optimally.
  
• Use Quality Hydraulic Fluid: Using the manufacturer's recommended hydraulic fluid can prevent contamination and ensure proper system operation.
  

Conclusion
Hydraulic system overpressure in the Takeuchi TB135 can lead to engine bogging and hydraulic tank bulging, indicating potential damage. By understanding the causes and implementing effective troubleshooting and maintenance practices, operators can ensure the longevity and performance of their equipment. Regular inspections and adherence to maintenance schedules are key to preventing such issues.