Removing the Lift and Tilt Control Valve on a Bobcat 853 Skid-Steer Loader

[MikePhua]

The Bobcat 853 Skid-Steer Loader, introduced in the early 1990s, was a significant advancement in compact construction machinery. Known for its versatility and robust hydraulic system, the 853 model became a staple for operators requiring reliable performance in tight spaces. However, like all machinery, the lift and tilt control valve can experience issues over time, necessitating removal and maintenance.
Understanding the Lift and Tilt Control Valve
The lift and tilt control valve on the Bobcat 853 is integral to the loader's hydraulic system, managing the flow of hydraulic fluid to the lift and tilt cylinders. This valve ensures precise control over the loader's movements, allowing operators to lift, tilt, and maneuver attachments with accuracy. The valve assembly comprises several components, including spools, springs, detents, and seals, all of which can wear or become damaged, leading to performance issues.
Common Issues Leading to Valve Removal
Operators may encounter various symptoms indicating that the lift and tilt control valve requires attention:

• Unresponsive Controls: When the lift or tilt functions do not respond to joystick inputs, it may signify internal valve issues.
  
• Erratic Movements: Inconsistent or jerky movements during lifting or tilting can result from worn or damaged valve components.
  
• Hydraulic Leaks: Visible hydraulic fluid leaks around the valve area often point to seal failures or damaged valve bodies.
  

Step-by-Step Guide to Removing the Control Valve

1. Preparation: Ensure the loader is on a stable surface, and engage the parking brake. Disconnect the battery to prevent accidental starts.
   
2. Relieve Hydraulic Pressure: Start the engine and operate the lift and tilt controls to relieve any residual hydraulic pressure. Turn off the engine before proceeding.
   
3. Accessing the Valve: Remove any panels or covers obstructing access to the control valve assembly. This may involve removing the seat or lifting the cab, depending on the machine's configuration.
   
4. Disconnect Hydraulic Lines: Carefully disconnect the hydraulic lines leading to the lift and tilt cylinders. Use appropriate containers to catch any residual hydraulic fluid.
   
5. Remove Mounting Bolts: Locate and remove the bolts securing the control valve to the loader frame. Keep these bolts for reinstallation.
   
6. Remove the Valve Assembly: Gently slide the control valve assembly out of its mounting position. Be cautious not to damage any surrounding components.
   

Inspecting and Servicing the Valve
Once removed, inspect the valve assembly for signs of wear or damage. Common issues include:

• Worn Seals: Seals can degrade over time, leading to hydraulic leaks.
  
• Damaged Spools: Spools may become scored or worn, affecting fluid flow and control precision.
  
• Debris Contamination: Dirt or metal particles can enter the valve, causing blockages or wear.
  

Cleaning the valve components with a suitable solvent and replacing any worn parts can restore functionality. It's advisable to consult the Bobcat 853 service manual for specific part numbers and procedures.
Reinstallation and Testing

1. Reassemble the Valve: After servicing, reassemble the control valve, ensuring all components are correctly installed.
   
2. Install the Valve: Position the valve assembly back into its mounting location on the loader frame. Secure it with the previously removed bolts.
   
3. Reconnect Hydraulic Lines: Reconnect the hydraulic lines to the lift and tilt cylinders, ensuring all connections are tight and leak-free.
   
4. Refill Hydraulic Fluid: Check the hydraulic fluid level and top up if necessary.
   
5. Test Operation: Start the engine and test the lift and tilt functions. Operate the controls through their full range to ensure smooth and responsive movements.
   

Maintenance Tips
To prolong the life of the lift and tilt control valve:

• Regular Inspections: Periodically check for signs of wear, leaks, or unusual noises.
  
• Hydraulic Fluid Maintenance: Keep the hydraulic fluid clean and at the proper level.
  
• Use Quality Parts: When replacing components, use genuine Bobcat parts to ensure compatibility and performance.
  

Conclusion
The lift and tilt control valve is a critical component of the Bobcat 853 Skid-Steer Loader's hydraulic system. Understanding its function and maintaining it properly ensures the loader operates efficiently and reliably. By following the outlined procedures for removal, inspection, and reinstallation, operators can address common hydraulic issues and extend the service life of their equipment.