Bleeding Electric Over Hydraulic Brakes: How to Bleed?

Bleeding electric over hydraulic brakes is a critical maintenance task to ensure that your trailer’s braking system functions properly. Whether you are dealing with a new installation or performing routine maintenance, knowing how to effectively bleed these brakes can make the difference in safety and performance. In this guide, we will explore the bleeding process for electric over hydraulic brakes, why it is necessary, and the steps you need to follow to ensure your trailer’s brake system is functioning optimally.

What are Electric Over Hydraulic Brakes?

Electric over hydraulic (EOH) brake systems combine the precision of electric control with the strength of hydraulic brakes. This system is commonly used in trailers, especially for heavier loads where increased braking power is necessary. The EOH system uses an electric actuator to pressurize hydraulic fluid, which then applies the brake force to the wheels.

The bleeding process is crucial for removing any air that might have entered the hydraulic lines. Air bubbles can reduce the efficiency of the brakes and compromise safety. Properly bleeding the brakes ensures that only hydraulic fluid is present in the system, allowing for smooth and powerful braking.

Mechanic bleeding electric over hydraulic brakes on a trailer, focusing on brake calipers and bleeder valves.

Why Bleeding Electric Over Hydraulic Brakes is Necessary

The Importance of Maintaining Brake Performance

Bleeding the brakes is an essential maintenance procedure for ensuring the reliability of electric over hydraulic brakes. Air trapped in the brake lines can compress under pressure, causing a loss of braking power. This can result in delayed or uneven braking, which is especially dangerous when towing heavy loads. Regularly bleeding the brake system helps maintain maximum braking efficiency, ensuring that your trailer can stop smoothly and safely.

When Should You Bleed Electric Over Hydraulic Brakes?

There are several scenarios when bleeding the brakes is necessary:

  • After Installation: If you’ve just installed a new EOH braking system, bleeding the brakes is required to remove any air that may have entered the lines during installation.
  • Regular Maintenance: As part of routine trailer maintenance, it’s recommended to bleed the brakes every 12-24 months, depending on usage.
  • Brake Fluid Replacement: Whenever you replace the hydraulic fluid, it’s important to bleed the system to remove any trapped air.
  • Brake Performance Issues: If you notice that your trailer’s brakes feel soft or spongy, or if braking power has decreased, bleeding the brakes may resolve the issue.

How to Bleed Electric Over Hydraulic Brakes: Step-by-Step

Step 1: Prepare the Necessary Tools and Equipment

Before you begin bleeding the brakes, make sure you have all the necessary tools and equipment:

  • Brake bleeding kit (which includes a tube and catch bottle)
  • Wrenches (to fit the bleeder valve)
  • Brake fluid recommended for your EOH system
  • Protective gloves and safety glasses
  • Jack and jack stands (if necessary to lift the trailer)
  • Rags for cleaning up any spilled brake fluid

Step 2: Locate the Bleeder Valves

Each brake caliper on your trailer will have a bleeder valve. These valves allow you to release air and old brake fluid from the system. You’ll typically find the bleeder valve near the top of the brake caliper. Make sure you can access these valves easily before starting the bleeding process.

Step 3: Connect the Bleeder Hose and Open the Valve

Attach one end of the bleeding kit hose to the bleeder valve and place the other end into a container to catch the old brake fluid. Once everything is securely connected, use a wrench to loosen the bleeder valve. Be cautious as brake fluid will begin to flow out once the valve is open.

Step 4: Activate the Electric Over Hydraulic Actuator

With the bleeder valve open, activate the electric over hydraulic actuator. This is typically done by applying pressure to the brake controller inside the towing vehicle. As the actuator pressurizes the system, brake fluid will flow out of the bleeder valve, carrying any air bubbles with it.

Step 5: Monitor the Brake Fluid Flow

Continue applying pressure to the brake controller until you see a steady stream of fluid without any air bubbles. It’s important to keep an eye on the fluid level in the brake fluid reservoir during this process. Refill the reservoir as needed to ensure that air doesn’t re-enter the system.

Step 6: Close the Bleeder Valve and Repeat

Once you see a consistent stream of fluid free from air bubbles, close the bleeder valve securely. Repeat this process for each brake caliper on the trailer. It’s important to bleed each caliper individually to ensure that all air is removed from the system.

Step 7: Test the Brakes

After all the brakes have been bled, it’s time to test the system. Re-engage the electric over hydraulic actuator and test the brakes by applying the brake controller in the towing vehicle. The brakes should feel firm and responsive, without any softness or sponginess.

Step 8: Check for Leaks

Finally, inspect the system for any leaks. Check around the bleeder valves, brake lines, and hydraulic actuator for any signs of fluid leakage. If everything looks good, you’ve successfully bled your electric over hydraulic brakes.

Common Mistakes to Avoid When Bleeding Electric Over Hydraulic Brakes

Forgetting to Refill the Brake Fluid Reservoir

One of the most common mistakes during the bleeding process is allowing the brake fluid reservoir to run dry. This can introduce more air into the system, undoing your hard work and requiring you to start the bleeding process over.

Skipping Brake Calipers

Ensure you bleed all the brake calipers on your trailer. Skipping even one can leave air trapped in the system, reducing braking performance.

Not Securing the Bleeder Valves Properly

After bleeding each caliper, be sure to securely close the bleeder valve to prevent any air or fluid from escaping. Failing to do so can result in brake fluid leaks or air re-entering the system.

Preventative Maintenance for Electric Over Hydraulic Brakes

Regular Fluid Checks and Replacements

To keep your electric over hydraulic brake system functioning properly, regularly check the brake fluid levels. Replace the brake fluid every 1-2 years to prevent contamination or degradation.

Inspect Brake Components Annually

Regularly inspect the brake components, including the calipers, rotors, and brake lines, for wear and tear. Address any issues promptly to prevent them from affecting brake performance.

Conclusion

Bleeding electric over hydraulic brakes is a vital maintenance procedure that ensures the safety and performance of your trailer’s braking system. By following the steps outlined in this guide, you can effectively remove air from the system, restore braking power, and keep your trailer in peak condition. Regular maintenance, including fluid replacement and brake inspections, will help prolong the life of your braking system and ensure safe towing experiences.

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