Bleeding your trailer brakes in New Zealand is crucial for ensuring safe and effective braking performance. It involves removing air bubbles from the hydraulic brake lines, restoring a firm pedal feel and allowing for optimal stopping power, essential for navigating varied NZ terrain.
Why Bleed Trailer Brakes?
Trailer brakes, like those on cars and trucks, rely on a hydraulic system to transmit force from the actuator to the brake shoes or pads. Over time, air can enter this system, typically through loose fittings, damaged lines, or during repairs. Air is compressible, unlike brake fluid, and its presence diminishes the hydraulic pressure, leading to spongy brakes, reduced stopping power, and potentially dangerous situations, particularly on New Zealand’s often steep and winding roads. Regularly bleeding your trailer brakes is a vital part of preventative maintenance.
Tools and Materials You’ll Need
Before you begin, gather the necessary tools and materials:
- Brake fluid: Use the type specified in your trailer’s manual. DOT 3 is common, but always confirm.
- Bleeder wrench: A specialized wrench designed to fit the bleeder screws on the brake cylinders or calipers.
- Clear plastic tubing: To connect to the bleeder screw and direct the fluid into a container.
- Collection container: An empty bottle or jar to catch the old brake fluid.
- Jack and jack stands: To safely lift and support the trailer.
- Wheel chocks: To secure the wheels that are not being worked on.
- Rags or paper towels: To clean up any spills.
- Gloves: To protect your hands from brake fluid, which can be corrosive.
- Safety glasses: To protect your eyes from splashes.
- Assistant (optional but highly recommended): Having someone to pump the brakes simplifies the process.
Bleeding the Brakes: Step-by-Step Guide
1. Safety First
- Park the trailer on a level surface.
- Engage the parking brake or use wheel chocks on the wheels that won’t be lifted.
- Loosen the lug nuts on the wheel you’ll be working on.
- Jack up the trailer and securely support it with jack stands. Never work under a trailer supported only by a jack.
- Remove the wheel.
2. Locate the Bleeder Screw
- The bleeder screw is a small valve located on the brake cylinder (drum brakes) or caliper (disc brakes). It typically has a rubber cap that needs to be removed. Clean around the bleeder screw with a rag to prevent debris from entering the brake system.
3. Prepare the Bleeding Setup
- Attach one end of the clear plastic tubing to the bleeder screw.
- Submerge the other end of the tubing in the collection container, ensuring the end is always submerged in brake fluid. This prevents air from being drawn back into the brake system.
4. Bleeding Procedure (Two-Person Method)
- Have your assistant pump the brake pedal several times and then hold it down firmly.
- While your assistant is holding the pedal down, use the bleeder wrench to carefully open the bleeder screw. You should see fluid and possibly air bubbles flowing into the tubing.
- Immediately after opening the bleeder screw, have your assistant tell you when the brake pedal reaches the floor. Close the bleeder screw tightly before the pedal reaches the floor. This prevents air from being sucked back into the system.
- Repeat steps 4 and 5 until clear, bubble-free brake fluid flows through the tubing.
- Regularly check the brake fluid reservoir in the actuator and top it off with fresh brake fluid as needed. Never let the reservoir run dry, as this will introduce more air into the system.
5. Bleeding Procedure (One-Person Method)
- There are one-person brake bleeding kits available that use a one-way valve to prevent air from being drawn back in. Follow the instructions that come with the kit.
- Alternatively, you can use the “gravity bleeding” method. Open the bleeder screw and let gravity slowly push the brake fluid through the system. Monitor the reservoir and top it off as needed. This method is slower but requires no assistance.
- Always ensure the end of the tubing remains submerged in brake fluid in the collection container.
6. Repeat for All Brakes
- Repeat the bleeding process for each brake on the trailer, starting with the brake furthest from the actuator and working your way closer. This ensures that the entire system is properly bled. A common sequence is right rear, left rear, right front, left front.
7. Final Checks and Reassembly
- After bleeding all the brakes, tighten all bleeder screws securely.
- Replace the rubber caps on the bleeder screws.
- Top off the brake fluid reservoir to the correct level.
- Reinstall the wheels.
- Lower the trailer and remove the jack stands.
- Tighten the lug nuts to the correct torque specification.
- Perform a brake test in a safe, controlled environment before using the trailer on public roads.
Identifying Potential Problems
- Spongy brake pedal: This is the most common symptom of air in the brake lines.
- Reduced stopping power: The trailer takes longer to stop than usual.
- Uneven braking: The trailer pulls to one side when braking.
- Leaking brake fluid: Inspect the brake lines, calipers, and wheel cylinders for leaks.
FAQs: Bleeding Trailer Brakes in NZ
1. How often should I bleed my trailer brakes?
You should bleed your trailer brakes at least once a year, or more frequently if you notice any signs of air in the system, such as a spongy brake pedal. Heavy use or rough terrain might warrant more frequent bleeding.
2. What type of brake fluid should I use?
Always use the type of brake fluid specified in your trailer’s manual. DOT 3 is common, but DOT 4 or DOT 5.1 are sometimes recommended. Never mix different types of brake fluid.
3. Can I bleed my trailer brakes myself, or do I need a professional?
You can bleed your trailer brakes yourself if you are comfortable working on your trailer and have the necessary tools and knowledge. However, if you are unsure about any part of the process, it is best to consult a qualified mechanic.
4. What happens if I get brake fluid on my paint?
Brake fluid is corrosive and can damage paint. If you spill brake fluid on your trailer’s paint, immediately wash it off with soap and water.
5. How do I know if I have a brake fluid leak?
Look for wet spots around the brake lines, calipers, or wheel cylinders. You may also notice a drop in the brake fluid level in the reservoir.
6. What is the correct torque specification for the bleeder screws?
The torque specification for the bleeder screws is usually quite low. Refer to your trailer’s manual or a reliable repair manual for the correct value. Over-tightening can damage the bleeder screw.
7. What is a brake actuator, and where is it located?
The brake actuator is the mechanism that applies the trailer brakes. It’s typically located at the front of the trailer, near the hitch. It’s activated by inertia when the tow vehicle brakes.
8. What are electric trailer brakes, and how do they differ from hydraulic brakes?
Electric trailer brakes use electromagnets to apply the brakes, rather than hydraulic pressure. They require a different type of controller in the tow vehicle. Bleeding is not required for electric brakes.
9. Can I reuse brake fluid?
Never reuse brake fluid. Brake fluid absorbs moisture from the air, which can corrode brake system components and reduce braking performance.
10. What do I do if the bleeder screw is stuck or broken?
If the bleeder screw is stuck, try applying penetrating oil and letting it soak for a while before attempting to loosen it. If the bleeder screw is broken, you may need to replace the entire brake cylinder or caliper.
11. What are surge brakes?
Surge brakes are a type of hydraulic trailer brake that is activated by the inertia of the trailer pushing against the tow vehicle when the tow vehicle brakes. They are commonly used on boat trailers.
12. How important is it to have a brake controller in my tow vehicle when using electric brakes on a trailer in NZ?
Having a functioning brake controller is absolutely essential when towing a trailer equipped with electric brakes in New Zealand. It’s a legal requirement and significantly enhances safety by allowing you to adjust the trailer’s braking force independently, preventing jackknifing and ensuring controlled stops, especially important on hilly terrains.
By following these steps and taking the necessary precautions, you can safely and effectively bleed your trailer brakes and ensure optimal braking performance for your New Zealand adventures. Remember, safety is paramount. When in doubt, consult a qualified professional.