Why Does an Excavator Boom Arm Sometimes Rise Automatically?

[MikePhua]

In this discussion, users explore the issue of excavator boom arms rising on their own during operation. Various possible causes and solutions are shared.
Main Causes:

• Hydraulic System Leakage
  The most common cause is leakage in the hydraulic cylinder’s check valve or seals, causing hydraulic oil to flow back and the boom arm to slowly rise without operator input.
  
• Hydraulic Circuit Design
  Some excavators are designed with hydraulic circuits that allow slow oil flow, which may naturally cause slight boom arm movement upward.
  
• Load Effects
  The boom arm’s weight and load distribution can create an unbalanced force on the hydraulic cylinder, pushing hydraulic oil and causing the boom to rise.
  
• Control Valve Malfunction
  Worn or stuck control valves on the joystick can lead to hydraulic oil leakage or poor control, resulting in the boom arm rising by itself.
  

Maintenance and Inspection Suggestions:

• Inspect hydraulic cylinder seals and replace damaged check valves.
  
• Confirm control valves are functioning properly.
  
• Maintain clean and sufficient hydraulic oil levels.
  

Summary:
Automatic boom arm rising is typically caused by hydraulic system leaks or control valve faults—especially failed check valves or aging seals causing oil backflow. Load distribution and circuit design also contribute. Solutions include repairing cylinders, replacing seals and valves, and ensuring the hydraulic system works properly to prevent leaks. Regular maintenance and prompt troubleshooting help avoid safety risks associated with unintended boom movement.