Volvo L70H Wheel Loader: Troubleshooting Hydraulic Hunting Issues

[MikePhua]

The Volvo L70H wheel loader is renowned for its robust performance and advanced hydraulic systems. However, operators occasionally encounter a phenomenon known as "hunting"—a rhythmic, unintended movement of the loader's lifting arms or bucket. This issue can disrupt operations and lead to increased wear if not addressed promptly.
Understanding Hydraulic Hunting
Hydraulic hunting refers to the oscillatory motion of hydraulic actuators, such as lift arms or tilt cylinders, caused by pressure fluctuations within the hydraulic system. These fluctuations can result from various factors, including system design, component wear, or external influences.
Common Causes of Hydraulic Hunting

1. Variable Displacement Pump Instability
   The L70H utilizes a variable displacement axial piston pump to supply hydraulic fluid. If the pump's control system malfunctions or becomes unstable, it can cause pressure variations, leading to hunting. Regular maintenance and calibration are essential to ensure pump stability.
   
2. Pressure Relief Valve Malfunctions
   The pressure relief valve regulates the maximum pressure within the hydraulic system. If this valve becomes stuck or fails to open at the correct pressure, it can cause pressure spikes, contributing to hunting. Periodic inspection and testing of the relief valve are recommended.
   
3. Air Entrapment in the Hydraulic Fluid
   Air bubbles within the hydraulic fluid can compress and expand, causing erratic actuator movement. This can result from leaks in the suction line, faulty seals, or improper fluid levels. Ensuring airtight seals and proper fluid maintenance can mitigate this issue.
   
4. Control Valve Spool Sticking
   The control valve directs hydraulic fluid to various actuators. If the valve spool becomes sticky or sluggish due to contamination or wear, it can cause intermittent fluid flow, leading to hunting. Regular cleaning and inspection of the control valve are advisable.
   
5. Cylinder Seal Degradation
   Worn or damaged seals in hydraulic cylinders can lead to internal leakage, reducing the effectiveness of the actuator and causing unstable movement. Replacing seals at the first sign of wear can prevent hunting and other related issues.
   

Diagnostic Steps

• Monitor Pressure Fluctuations: Use a pressure gauge to observe any irregularities in the system's pressure readings.
  
• Inspect Hydraulic Fluid: Check for signs of contamination, air bubbles, or incorrect fluid levels.
  
• Examine Components: Look for visible signs of wear or damage in the pump, valves, and cylinders.
  
• Test Relief Valve: Ensure the pressure relief valve operates correctly at the specified pressure setting.
  

Preventive Measures

• Regular Maintenance: Adhere to the manufacturer's recommended maintenance schedule, including fluid changes and component inspections.
  
• Use Quality Components: Replace worn or damaged parts with OEM (Original Equipment Manufacturer) components to ensure compatibility and reliability.
  
• Proper Training: Ensure operators are trained to recognize early signs of hunting and understand the importance of timely maintenance.
  

Case Study: Addressing Hunting in the L70 Series
A notable instance of hunting issues in Volvo loaders occurred with the L70 series. Operators reported intermittent hunting during lifting operations, particularly under load. Upon investigation, it was found that a combination of factors, including air in the hydraulic fluid and a malfunctioning pressure relief valve, contributed to the problem. By addressing these issues through comprehensive maintenance and component replacement, the hunting behavior was effectively eliminated.
Conclusion
Hydraulic hunting in the Volvo L70H wheel loader, while disruptive, can be effectively managed through diligent maintenance and prompt attention to system components. By understanding the underlying causes and implementing preventive measures, operators can ensure smooth and efficient operation of their equipment.