drum brake bleeding

How to Properly Bleed Drum Brakes A Comprehensive Guide

Drum brakes are a common braking system found in many vehicles, especially in older models and on the rear axles of newer cars. One essential maintenance task for keeping drum brakes functioning effectively is the process of bleeding them. Bleeding drum brakes removes trapped air from the brake lines, ensuring that the braking system operates smoothly and efficiently. This article provides a step-by-step guide on how to bleed drum brakes, along with some tips to make the process easier.

Understanding the Importance of Bleeding

When you apply the brake pedal, hydraulic pressure is generated in the brake lines, which pushes the brake shoes against the drum, slowing down or stopping the vehicle. However, if air gets into the brake lines, it compresses when you press the pedal, leading to a spongy or unresponsive brake feel. This could severely compromise your vehicle's safety. Bleeding the brakes is crucial after any brake maintenance, including replacing brake fluid, installing new brake components, or if you experience any brake performance issues.

Tools and Materials Needed

Before you begin, gather the necessary tools and materials - A brake bleeder kit or a clear plastic tube and a container - Brake fluid (ensure it’s the correct type for your vehicle) - A wrench (usually 10mm or 12mm, depending on your brake system) - A jack and jack stands - A tire iron - Safety goggles and gloves

Step-by-Step Process

1. Preparation

Start by lifting the vehicle with a jack and securing it on jack stands. Ensure you are working on a flat, stable surface. Remove the wheel covering the drum brake you intend to bleed.

2. Locate the Bleeder Screw

The bleeder screw is typically located on the brake cylinder or drum assembly and is often covered by a rubber cap. Remove the rubber cap to access the bleeder screw.

3. Attach the Bleeder Kit

If using a brake bleeder kit, attach the hose to the bleeder screw. Ensure the other end of the hose is submerged in a container with some brake fluid. This setup will help catch any fluid while preventing air from returning to the brake line.

4. Pump the Brake Pedal

Have a partner sit in the driver's seat and pump the brake pedal several times (approximately 5-7 times) and then hold it down firmly. This action builds up hydraulic pressure in the brake lines.

5. Open the Bleeder Screw

While your partner is holding the pedal down, use the wrench to carefully open the bleeder screw. You should hear a hissing noise as air and brake fluid escape through the hose into the container. Once the pedal goes to the floor, close the bleeder screw before your partner releases the brake pedal. This step prevents air from re-entering the system.

6. Repeat the Process

Repeat the process of pumping, holding, opening the bleeder screw, and closing it several times until you see a steady stream of clear brake fluid without any air bubbles. This indicates that the air has been successfully bled from the system.

7. Check Brake Fluid Levels

Throughout the process, make sure to check the brake fluid reservoir and refill if necessary to prevent air from entering the system. This is crucial as low fluid levels can lead to an incomplete bleeding process.

8. Finishing Up

Once you've bled all the brakes (start with the wheel farthest from the master cylinder and work your way closer), replace the bleeder screw caps and reassemble the wheel. Lower the vehicle and test the brakes before driving.

Conclusion

Bleeding drum brakes is a straightforward yet crucial maintenance process. Regular checks and bleeding as needed can help ensure optimal brake performance and vehicle safety. If at any point you feel uncertain or uncomfortable performing this task, do not hesitate to seek professional help. Remember, safe brakes are vital for your safety on the road!