Adjusting Hydraulic Thumb Pressure on the Yanmar VIO35-5 Mini Excavator

[MikePhua]

Introduction
The Yanmar VIO35-5 is a compact, zero-tail-swing mini excavator renowned for its versatility and performance in confined spaces. Equipped with advanced hydraulic systems, it offers operators the flexibility to use various attachments, including hydraulic thumbs and breakers. To ensure optimal performance and prevent damage to attachments, it's crucial to adjust the hydraulic pressure settings appropriately.
Understanding Hydraulic Pressure Settings
Hydraulic systems in excavators operate under specific pressure settings to ensure efficient and safe operation. Attachments like hydraulic thumbs and breakers require different pressure levels to function correctly. For instance, a hydraulic thumb typically operates at a lower pressure than a breaker to prevent overloading and potential damage.
Adjusting Pressure for Hydraulic Thumb Operation
To adjust the hydraulic pressure for the thumb circuit on the Yanmar VIO35-5, follow these steps:

1. Locate the Relief Valve: Identify the relief valve associated with the auxiliary hydraulic circuit.
   
2. Loosen the Jamb Nut: Using a 17mm wrench, loosen the jamb nut securing the relief valve.
   
3. Adjust the Allen Stem: Insert an Allen wrench into the valve and turn the stem inward by approximately 60 degrees.
   
4. Test the Pressure: After adjustment, test the hydraulic thumb's operation. The relief valve should be set to 400–500 psi above the tool's operating pressure.
   
5. Fine-Tune as Necessary: If the thumb operates too forcefully or not enough, make incremental adjustments to the relief valve until the desired performance is achieved.
   

Converting Hydraulic Circuit for Breaker Use
When switching from a thumb to a breaker, it's essential to adjust the hydraulic system to accommodate the higher pressure requirements of the breaker. This typically involves:

• Adjusting the Relief Valve: Increase the pressure setting to match the breaker’s specifications.
  
• Switching the Valve Position: Some models may require changing the valve position to direct flow appropriately.
  
• Consulting the Operator's Manual: Always refer to the specific model's manual for detailed instructions on converting the hydraulic circuit.
  

Safety Precautions

• Pressure Testing: Before making adjustments, use a hydraulic pressure gauge to verify the current pressure settings.
  
• Incremental Adjustments: Make small adjustments and test the system's response to avoid over-pressurization.
  
• Professional Assistance: If unsure about the adjustment process, consult a certified technician to ensure the system is set up correctly.
  

Conclusion
Properly adjusting the hydraulic pressure settings on the Yanmar VIO35-5 is crucial for the efficient operation of attachments like hydraulic thumbs and breakers. By following the outlined procedures and safety precautions, operators can ensure optimal performance and longevity of their equipment. Always refer to the specific model's manual for detailed instructions and consult professionals when necessary.