Yes, you can bleed trailer surge brakes by yourself, but it requires a specific technique and a bit of ingenuity. Using a combination of gravity bleeding, a one-person brake bleeder, and potentially a locking clamp, you can achieve a firm brake pedal and restore optimal braking performance to your trailer.
Understanding Surge Brakes
Surge brakes are a type of trailer braking system that relies on the inertia of the trailer pushing against the tow vehicle to activate the brakes. When you slow down in your tow vehicle, the trailer ‘surges’ forward, compressing a master cylinder located at the front of the trailer. This master cylinder then sends hydraulic fluid to the brake cylinders at each wheel, engaging the brakes. Properly functioning surge brakes are crucial for safe towing, preventing jackknifing and ensuring controlled stopping distances.
The Importance of Bleeding Your Trailer Brakes
Over time, air can enter the hydraulic brake lines in your trailer. This air compresses, preventing the full force of the master cylinder from reaching the brake cylinders. The result is a spongy brake pedal, reduced braking effectiveness, and potentially dangerous towing conditions. Bleeding your brakes removes this trapped air, restoring a firm pedal feel and ensuring optimal braking performance. Ignoring air in the brake lines can lead to brake failure in emergency situations.
Preparing to Bleed Your Surge Brakes
Before you begin, gather the necessary tools and materials:
- Wrench: A wrench of the correct size to open and close the bleeder screws on each brake cylinder. Be sure to use the correct size to avoid stripping the bleeder screw.
- Clear Tubing: A length of clear tubing that fits snugly over the bleeder screws.
- Catch Jar or Container: To collect the brake fluid as it is bled.
- Brake Fluid: The correct type of brake fluid for your trailer’s system (DOT 3 or DOT 4 are common). Do not mix different types of brake fluid.
- Locking Clamp (Optional): A locking clamp or vise grips to depress the surge coupler for bleeding.
- One-Person Brake Bleeder Kit (Optional): A kit with a one-way valve and hose to prevent backflow of air into the brake lines.
- Safety Glasses and Gloves: To protect your eyes and skin from brake fluid.
The Bleeding Process: Step-by-Step
Step 1: Secure Your Trailer
Ensure the trailer is properly supported and level. Disconnect it from the tow vehicle. Use wheel chocks to prevent any movement.
Step 2: Locate the Bleeder Screws
Locate the bleeder screws on the back of each brake assembly (typically on each wheel). These screws allow you to release the trapped air from the brake lines.
Step 3: Connect the Tubing
Attach one end of the clear tubing to a bleeder screw. Place the other end of the tubing into your catch jar, ensuring the end of the tube is submerged in a small amount of fresh brake fluid. This prevents air from being drawn back into the brake system.
Step 4: Depress the Surge Coupler
This is where the solo part comes in. You need to depress the surge coupler to activate the master cylinder. You can accomplish this using:
- Locking Clamp Method: Use a locking clamp or vise grips to carefully depress the surge coupler. Secure the clamp in a position that allows you to open and close the bleeder screw simultaneously. Be careful not to damage the coupler.
- One-Person Bleeder Kit Method: Connect the one-person bleeder kit to the bleeder screw according to the kit’s instructions. These kits usually have a one-way valve that prevents backflow.
Step 5: Open the Bleeder Screw
With the surge coupler depressed (using either method), slightly loosen the bleeder screw. You should see brake fluid flowing through the tubing into the catch jar. Look for air bubbles in the fluid.
Step 6: Close the Bleeder Screw
While keeping the surge coupler depressed, tighten the bleeder screw before releasing the coupler. This prevents air from being drawn back into the system as the coupler extends.
Step 7: Repeat the Process
Repeat steps 4-6 until no more air bubbles appear in the brake fluid flowing through the tubing. Ensure the reservoir of the surge brake master cylinder is filled with fluid throughout the bleeding process. Never let the reservoir run dry, as this will introduce more air into the system.
Step 8: Bleed Each Wheel Cylinder
Repeat steps 3-7 for each brake cylinder, starting with the one farthest from the master cylinder and working your way closer. This ensures that all air is bled from the entire system.
Step 9: Test Your Brakes
After bleeding all the brake cylinders, reconnect the trailer to your tow vehicle. Before heading out on the road, thoroughly test the brakes in a safe, controlled environment. Ensure the brakes engage smoothly and firmly.
Frequently Asked Questions (FAQs)
FAQ 1: How do I know if my trailer brakes need bleeding?
You’ll typically notice a spongy brake pedal or reduced braking power. The trailer might take longer to stop, or you may feel a lack of confidence in the brakes’ performance. Visual inspection of the brake fluid for contamination or low levels in the master cylinder can also be an indicator.
FAQ 2: What type of brake fluid should I use?
Refer to your trailer’s owner’s manual. Most trailers use DOT 3 or DOT 4 brake fluid. Never mix different types of brake fluid. Using the wrong type can damage the brake system’s seals and components.
FAQ 3: Can I use a vacuum bleeder instead?
Yes, a vacuum bleeder can be used on trailer surge brakes. Connect the vacuum bleeder to the bleeder screw and follow the manufacturer’s instructions. Ensure the surge coupler is depressed during the process.
FAQ 4: How often should I bleed my trailer brakes?
It depends on usage and environmental factors. A good rule of thumb is to bleed your trailer brakes annually or whenever you notice a decrease in braking performance. If you tow frequently or in harsh conditions, you may need to bleed them more often.
FAQ 5: What if I can’t get the bleeder screw to open?
Penetrating oil can help loosen a stuck bleeder screw. Apply the oil to the screw threads and let it sit for a few hours before attempting to open it. If it still won’t budge, you may need to replace the bleeder screw or seek professional help. Avoid forcing it, as you could break the screw.
FAQ 6: What if the master cylinder runs dry during bleeding?
If the master cylinder runs dry, air will be introduced into the entire system, requiring a more extensive bleeding process. You may need to bleed the master cylinder itself first before bleeding the wheel cylinders.
FAQ 7: How do I bleed the master cylinder on a surge brake system?
Some surge brake master cylinders have a bleeder screw. Open it while depressing the surge coupler to remove air. If there’s no bleeder screw, repeatedly depress the surge coupler and release it quickly to force air out.
FAQ 8: What is the proper torque for tightening the bleeder screws?
The proper torque is typically 8-12 ft-lbs. Overtightening can damage the bleeder screw or the brake cylinder. Refer to your trailer’s service manual for specific torque specifications.
FAQ 9: Can I reuse the brake fluid that I bleed out?
No, never reuse brake fluid. Brake fluid absorbs moisture and contaminants, which can damage the brake system. Always use fresh, clean brake fluid.
FAQ 10: What if my brakes still feel spongy after bleeding?
Double-check all connections for leaks. Ensure the brake lines are in good condition. There may be a more serious issue, such as a faulty master cylinder or brake cylinders, requiring professional diagnosis and repair. Consider having a qualified mechanic inspect your brakes.
FAQ 11: Is there a specific pattern I should follow when bleeding each wheel?
Yes, always start with the wheel farthest from the master cylinder and work your way closer. This ensures the entire system is properly bled of air.
FAQ 12: Can I damage anything by bleeding the brakes incorrectly?
Yes, you can damage the surge coupler, brake lines, or brake cylinders by using excessive force or improper techniques. Always be gentle and methodical, and if you’re unsure about any step, consult a professional mechanic. Using the wrong type of brake fluid can also cause significant damage.
Bleeding your trailer’s surge brakes by yourself is achievable with the right tools, knowledge, and patience. Following these steps and FAQs will help you ensure safe and effective braking performance for your trailer. If you are uncomfortable performing this task, seek assistance from a qualified mechanic.