How To Bleed Hydraulic System On Skid Steer

Understanding Skid Steer Hydraulic Systems and Bleeding

Skid steer loaders utilize hydraulic systems for power. Air trapped within these systems can negatively affect performance. Bleeding the system removes this air, restoring optimal function. Specific procedures can vary slightly based on the make and model of the skid steer.

Safety Precautions Before Bleeding

Safety First: Always consult the manufacturer's operation and maintenance manual for specific safety instructions for your particular skid steer model before initiating any maintenance or repair procedures.

Personal Protective Equipment (PPE) such as safety glasses and gloves are required. Engage the parking brake and chock the wheels to prevent movement. Allow the machine to cool down, particularly if the hydraulic system has been operating under load, minimizing the risk of burns from hot hydraulic fluid. Be aware of the location of all hydraulic lines and fittings to avoid accidental contact, and ensure that the work area is well-ventilated and free of obstructions.

Identifying the Need for Bleeding

Erratic or jerky movements of the loader arms, bucket, or other hydraulically operated attachments can indicate air in the system. Reduced overall hydraulic power, slower response times, and unusual noises emanating from the hydraulic pump may also suggest the presence of air. Visual inspection of the hydraulic fluid reservoir might reveal foamy or milky-looking fluid, a clear indication of aeration.

Tools and Materials Required

You will need a wrench set (metric or SAE, depending on your machine), a screwdriver set, hydraulic fluid compatible with your skid steer model, a clean drain pan, rags or absorbent pads to clean up spills, and the machine's operation and maintenance manual. A helper may be beneficial for some procedures.

General Bleeding Procedure

Note: This is a general procedure. Always consult your machine's service manual for specific instructions.

Step 1: Locate Bleed Points

Hydraulic cylinders, the hydraulic pump, and sometimes the control valve will have bleed screws or valves. Consult your service manual for their precise location. Typically, these are small screws or fittings located on the cylinder or pump housing.

Step 2: Prepare the System

Ensure the hydraulic fluid reservoir is filled to the correct level. This prevents air from being drawn into the system during the bleeding process. Position a drain pan beneath the bleed point to catch any spilled fluid.

Step 3: Loosen the Bleed Screw

Using the appropriate wrench, carefully loosen the bleed screw or valve. Do not remove it completely. Loosen it just enough to allow fluid and air to escape.

Step 4: Actuate the Hydraulic System

With the bleed screw open, slowly operate the hydraulic function associated with the cylinder or pump being bled. For example, if bleeding a loader arm cylinder, slowly raise and lower the loader arms. Observe the fluid flowing from the bleed screw.

Step 5: Observe Fluid Flow

Initially, you will likely see air bubbles mixed with the hydraulic fluid. Continue actuating the hydraulic system until a steady stream of bubble-free fluid flows from the bleed screw.

Step 6: Tighten the Bleed Screw

Once a steady stream of fluid is observed, carefully tighten the bleed screw or valve while the hydraulic system is still being actuated. Avoid overtightening, as this can damage the screw or fitting.

Step 7: Repeat for All Bleed Points

Repeat steps 3 through 6 for each bleed point in the hydraulic system, starting with the cylinders furthest from the hydraulic pump and progressing towards the pump itself. This ensures that air is effectively purged from the entire system.

Step 8: Check Fluid Level

After bleeding all the points, recheck the hydraulic fluid level in the reservoir. Add fluid as needed to bring it to the correct level. Air being purged from the system will lower the fluid level.

Step 9: Test the System

Operate all hydraulic functions through their full range of motion. Check for smooth, responsive movements and the absence of unusual noises. If any issues persist, repeat the bleeding process or consult a qualified mechanic.

Specific Bleeding Procedures for Common Skid Steer Components

Bleeding Loader Arm Cylinders

Raise the loader arms slightly off the ground for stability. Locate the bleed screws on the loader arm cylinders. Loosen the bleed screw and slowly raise and lower the arms, observing the fluid flow. Tighten the screw when a bubble-free stream is present.

Bleeding Tilt Cylinder

Angle the bucket forward slightly. Locate the bleed screw on the tilt cylinder. Loosen the screw and slowly tilt the bucket back and forth, observing the fluid flow. Tighten the screw when a bubble-free stream is present.

Bleeding the Hydraulic Pump

The hydraulic pump may have one or more bleed screws. Refer to the service manual for the exact location. With the engine running at a low idle (check manual for specific RPM), loosen the bleed screw and allow fluid to flow until bubble-free. Tighten the screw.

Bleeding Drive Motors (If Applicable)

Some skid steers may have bleed points on the drive motors. Raise the machine so the wheels are off the ground and can spin freely. Locate the bleed screws on the drive motors. Loosen the bleed screw and gently engage the drive, allowing the wheels to rotate. Observe the fluid flow and tighten the screw when a bubble-free stream is present. Exercise caution to avoid sudden wheel movement. Support the machine securely before raising the wheels off the ground.

Troubleshooting Common Issues

If air continues to enter the system after bleeding, inspect hydraulic lines and fittings for leaks. Even small leaks can allow air to be drawn into the system. Check the hydraulic fluid reservoir for proper sealing of the cap and breather. A faulty seal can allow air to enter. Verify the condition of the hydraulic pump and cylinders. Internal leaks within these components can also cause aeration. Inspect the suction line between the hydraulic reservoir and pump for any signs of damage or loose connections. A damaged or loose suction line is a common cause of air ingestion.

Hydraulic Fluid Considerations

Using the correct type of hydraulic fluid is critical. Refer to the manufacturer's recommendations for the appropriate fluid specification for your skid steer model. Using the wrong fluid can lead to system damage and reduced performance. Always use clean, new hydraulic fluid. Contaminated fluid can damage hydraulic components. Regularly inspect the fluid for signs of contamination, such as water or debris. Change the hydraulic fluid and filter according to the manufacturer's recommended service intervals. This helps maintain system cleanliness and prevent premature wear.

Professional Assistance

If you are not comfortable performing the bleeding procedure yourself, or if the problem persists after bleeding the system, consult a qualified hydraulic mechanic. They have the expertise and tools to diagnose and repair complex hydraulic system issues.

Key Takeaways

Bleeding a skid steer's hydraulic system is a routine maintenance task that can improve performance. Always prioritize safety and consult the machine's service manual. Proper identification of bleed points and a systematic bleeding procedure are essential. Regular maintenance, including fluid and filter changes, prevents air from entering the system. If problems persist, seek professional assistance.

Important Reminder: The information provided in this article is intended as a general guide only. Always refer to your skid steer's operation and maintenance manual for specific instructions and safety precautions. Failure to do so could result in personal injury or damage to the machine.