How to Bleed Rear Drum Brakes – A Step-by-Step Guide

Brake bleeding is a maintenance process in a vehicle where brake fluid is purged from the brake lines to remove any air bubbles that may have been trapped inside. The presence of air in the brake lines can cause a decrease in the efficiency of the braking system because air can be compressed, unlike brake fluid. When the brake pedal is pressed, the air in the lines gets compressed first before any significant pressure is applied to the brake fluid, resulting in a spongy feeling in the brake pedal and reduced stopping power.

Knowing how to bleed rear drum brakes is necessary to ensure the optimal performance of the braking system. Over time, air can get into the brake lines due to various factors such as a brake fluid leak, recent repairs or component replacement in the brake system, or simply the gradual ingress of air over time. When this happens, it can significantly compromise the braking performance of the vehicle. Therefore, it’s crucial to bleed the brakes to remove this air and ensure the safety and efficiency of the braking system.

Understanding Rear Drum Brakes

Drum brakes are a type of braking system commonly found in older vehicles and in the rear wheels of some modern cars. The system is named for the drum-like shape of the component where the braking action occurs. Inside this drum are two curved shoes that press against the inner surfaces of the drum when the brake pedal is pressed, creating friction that slows and eventually stops the vehicle.

Brake fluid plays a critical role in the function of drum brakes. When the brake pedal is pressed, brake fluid is forced from the master cylinder reservoir through the brake lines and into the wheel cylinders in the drum brakes. This action forces the brake shoes against the drum, slowing the vehicle. If air gets into these brake lines, it can significantly reduce the effectiveness of this process.

Hence, the importance of fresh brake fluid in maintaining the performance of drum brakes cannot be overstated.

Symptoms of Air in the Brake Lines

Soft or spongy brake pedal

One of the primary symptoms of air in the brake lines is a soft or spongy brakes feeling in the brake pedal. This is due to the compressible nature of air. When you press the brake pedal, instead of the hydraulic force being directly transmitted to the brake shoes to apply the brakes, it first compresses the air, reducing the immediate braking force and resulting in a soft or spongy feel in the pedal.

Decreased brake performance

Another symptom of air in the brake lines is decreased brake performance. The presence of air in the brake system reduces the amount of hydraulic force that can be applied to the brakes, which means the vehicle might not stop as quickly as it should. This can increase stopping distances, making it potentially unsafe, especially in situations where immediate braking is required.

Visible air bubbles in brake fluid reservoir

In some cases, you might also be able to see visible air bubbles in the brake fluid reservoir. These air bubbles can enter the brake lines and eventually cause the symptoms described above. However, not all air in the brake system is always visible in the reservoir, so the absence of visible bubbles does not necessarily mean that the system is free of air.

Safety Precautions and Tools Needed for Brake Bleeding

Bleeding rear drum brakes requires some specific tools and equipment. This typically includes a car jack and jack stands to safely lift and support the vehicle, a wrench to open the brake bleeder valves, a clear hose for directing the old brake fluid into a container, a suitable container to catch the old fluid, and new brake fluid as recommended by the vehicle manufacturer.

Safety should always be the top priority when working on a vehicle. Before starting, make sure the vehicle is parked on a flat, stable surface. Use the car jack and jack stands to lift and securely support the vehicle.

Always wear protective eyewear to prevent fresh fluid from splashing into your eyes, and gloves to protect your hands. Brake fluid should be handled with care as it is corrosive and can damage the car’s paintwork. Lastly, it’s essential to dispose of the old fluid responsibly as it’s hazardous to the environment.

Step-by-Step Guide to Bleeding Rear Drum Brakes

Elevating and securing the vehicle

The first step to bleed drum brakes is to elevate and secure the vehicle. This can be done by using a car jack to lift the rear end of the vehicle and then placing jack stands under the vehicle for additional safety. It’s crucial to ensure that the vehicle is stable before beginning any work to avoid accidents.

Use a lug wrench to loosen the lug nuts on the rear axle and remove the tires to gain access to the wheel cylinder and bleeder screw for each wheel.

Locating the bleed valve on the drum brake

Once the vehicle is safely elevated, locate the brake bleeder screw on the drum brake. It’s typically a small nut or bolt on the backside of the brake assembly. If you’re unsure, refer to the vehicle’s service manual to correctly identify it.

Attaching a clear tube to the bleed valve and submerging the other end in brake fluid

Next, attach a clear tube to the bleed valve. The other end of the tube should be submerged in a container filled with a little brake fluid. The clear tube allows you to see the old fluid and air bubbles being expelled from the brake system.

The process of pumping the brake pedal and opening the bleed valve

Have a helper pump the brake pedal a few times and then hold it down. While they’re holding down the pedal, use a wrench to open the brake bleeder screw. This process will force the brake fluid through the brake caliper and out the bleeder valve and clear plastic tubing into the container.

Repeating the bleeding process until no air bubbles appear

Close the brake bleeder valve before the helper releases the brake pedal to prevent air from being drawn back into the system. Repeat this process until no more small air bubbles appear in the fluid coming out of the tube. Once one brake is done, move on to one of the next.

Ensuring the brake fluid reservoir remains sufficiently filled during the bleeding process

Throughout this process, it’s crucial to ensure that the brake fluid reservoir remains sufficiently filled. If the reservoir is allowed to run dry, air can enter the system, which would require the bleeding process to start over.

Post-Bleeding Process

Checking the firmness of the brake pedal

Once you’ve bled all the brakes, depress the brake pedal to check for firmness. If it feels spongy, there might still be air in the lines, and you’ll need to repeat the bleeding process on all four wheels. The pedal should feel firm and responsive.

Road testing the vehicle for improved brake response

Before returning the vehicle to regular use, conduct a slow and careful road test. This will allow you to check for improved brake response and ensure that the bleeding air process was successful when you bleed drum brakes.

Checking for leaks

Finally, after the road test, check the bleeder screws and the brake master cylinder reservoir for any leaks. If you find a leak, it will need to be addressed immediately to prevent further brake performance issues.

You should also check each brake line as you look for leaks after your bleed brakes.

When to Seek Professional Help

If you continue to experience poor brake performance even after bleeding the brakes, it’s advisable to seek professional help. This might indicate a more serious issue with the brake system, such as worn brake shoes, a leaking brake line, a failing master cylinder, or other problems that require professional attention.

Brake fluid leaks are another sign that you should seek professional help. Brake fluid is crucial for the proper functioning of the brake system, and leaks can lead to decreased braking performance, which is a serious safety risk. A professional mechanic can locate the source of the leak and carry out the necessary repairs.

Bleeding brakes require some mechanical knowledge and comfort with handling vehicle maintenance tasks. If you’re not comfortable or familiar with the process, it’s better to seek professional help. Doing so will ensure the job is done correctly and safely.

Routine Maintenance and Inspection of Drum Brakes

Regular brake system inspections are essential for maintaining safe and effective braking performance. This includes checking the brake fluid level and condition, checking brake shoes for wear, and looking for signs of leaks or other damage. Regular inspections can help identify potential issues before they become serious problems.

The frequency of brake fluid changes can vary depending on the vehicle and brake fluid type, but a good general rule is to change the fluid every two years or 30,000 miles. However, always refer to the vehicle’s service manual for the manufacturer’s specific recommendations.

Some vehicle owners may consider upgrading from drum brakes to disc brakes for improved braking performance and easier maintenance. However, this is a significant modification that requires professional installation and can be quite costly. The advantages and disadvantages should be thoroughly considered.

FAQ’s

What is the purpose of bleeding rear drum brakes?

Answer: Bleeding rear drum brakes is important to remove any air bubbles that may have gotten into the brake fluid system. Air bubbles can cause the brakes to feel spongy or go to the floor when you press the pedal.

How often should I bleed rear drum brakes?

Answer: The frequency with which you should bleed rear drum brakes depends on a few factors, including the age and condition of your car, the type of brake fluid you use, and how often you drive. However, as a general rule, you should bleed your rear drum brakes every 2 years or 30,000 miles.

What tools do I need to bleed rear drum brakes?

Answer: The basic tools you will need to bleed rear drum brakes are:

• A clear plastic tube
• A container to catch the old brake fluid
• A wrench to open the bleeder screws
• A helper to press the brake pedal

What is the correct order to bleed rear drum brakes?

Answer: The correct order to bleed rear drum brakes is to start with the wheel that is furthest away from the master cylinder and work your way back. This will help to ensure that all of the air bubbles are removed from the brake fluid system.

What are the safety precautions I should take when bleeding rear drum brakes?

Answer: There are a few safety precautions you should take when bleeding rear drum brakes, including:

• Wear safety glasses to protect your eyes from flying debris.
• Wear work gloves to protect your hands from burns and sharp edges.
• Make sure the car is in park and the parking brake is engaged before you start working.
• Do not overfill the brake fluid reservoir.

Conclusion

Bleeding rear drum brakes is a crucial maintenance task that ensures the optimal performance of your vehicle’s braking system. This article has provided a step-by-step guide to bleeding drum brakes, from identifying the need for bleeding to the actual bleeding process and post-bleeding checks.

Regular maintenance, including brake bleeding and inspections, is essential for the longevity of your vehicle and your safety on the road. Always take the necessary safety measures when performing any maintenance tasks on your vehicle.

While many maintenance tasks can be carried out by the vehicle owner, it’s important to recognize when professional help is needed. If you experience continued braking issues after bleeding, encounter brake fluid leaks, or feel uncomfortable with the bleeding process, don’t hesitate to seek professional help to ensure your vehicle’s safety and performance.