How To Flush Brake Fluid: A Step-by-Step Guide

ByAgkidzone Staff

Updated: Nov 14, 2024

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Noticing that you have to press your brakes harder than usual or that your brake pedal feels spongy? It’s time to take action. These signs indicate that there might be air or moisture in your brake system, which can compromise your vehicle’s safety. Flushing your brake fluid is essential to remove these impurities and keep your braking system functioning smoothly. Don’t worry—it’s a manageable DIY project that you can tackle with a bit of preparation and teamwork.

Your Prep List

Before you dive into flushing your brake fluid, gather all the necessary tools and materials. You’ll need an 8mm wrench to loosen the bleeder bolts, two to three feet of 3/16- or ¼-inch clear plastic tubing, an empty semi-transparent plastic soda bottle, fresh brake fluid, a zip tie, and a reliable helper. While not mandatory, removing all four tires and elevating your car can provide better visibility and access to the brake lines. Avoid using old brake fluid, as it may contain air and impurities that can contaminate the system, making the flush ineffective.

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ABS Brakes

If your vehicle is equipped with an Anti-lock Braking System (ABS), it’s crucial to handle the brake fluid with care. ABS components operate under extremely high pressure, and even tiny particles can damage the valves and pumps. Regularly flushing the system with fresh brake fluid every couple of years helps prevent such issues. Keep in mind that some ABS systems use proprietary technology, which can be expensive to repair or replace if contaminated. Maintaining clean brake fluid is vital for the longevity and performance of your ABS.

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Homemade Flushing Tool

Creating your own flushing tool can save you time and money. Start by drilling a hole in the cap of your soda bottle and inserting the clear plastic tubing so that it touches the bottom of the bottle. Ensure the tubing fits snugly around the bleeder valve to create a tight seal. Use a zip tie to secure the hose to the cap, preventing it from slipping out during the flushing process. Fill the bottle with fresh brake fluid to about one-third full and screw the cap tightly. This setup allows fresh fluid to flow into the system while old fluid and air are expelled through the tubing.

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Top Off the Reservoir

Locate the master cylinder reservoir under your vehicle’s hood. Clean any dirt or debris from the exterior to prevent contamination during the flushing process. Check the fluid level in the reservoir and top it off if necessary. Maintaining the correct fluid level is crucial because running the reservoir too low can introduce air into the brake lines, undermining the effectiveness of the flush. Keeping the reservoir full ensures a steady flow of brake fluid throughout the process.

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Bleeding Order

The sequence in which you bleed the brakes depends on the location of your ABS. Start with the brake line that is farthest from the master cylinder. For vehicles with rear-mounted ABS, begin with the driver’s front brake, then move to the passenger rear, driver rear, and finally the passenger front. Follow a ‘Z’ pattern to ensure thorough flushing of the entire system. This method helps remove all trapped air and ensures that each brake line is properly cleaned before moving on to the next.

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Position the Tool

Once you’ve identified the farthest brake line, attach your homemade flushing tool securely to the bleeder valve. Make sure the tubing is firmly in place to prevent leaks and ensure that only brake fluid flows through the hose. Position the soda bottle lower than the brake line to allow gravity to assist in the flushing process. This setup helps maintain a continuous flow of fresh brake fluid into the system while old fluid and air are expelled into the bottle.

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Open the Valve

Carefully loosen the bleeder valve with your 8mm wrench. Be cautious not to over-tighten or strip the valve. Once the valve is slightly open, have your helper pump the brake pedal a few times and then hold it down. This action forces the old brake fluid and any trapped air out through the tubing and into the soda bottle. Close the valve before your helper releases the brake pedal to prevent air from re-entering the system. Repeat this process until you see a steady flow of clear, fresh brake fluid without any air bubbles in the tubing.

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Bleed the Line

Continue pumping and holding the brake pedal while your helper monitors the flow of brake fluid. Once the bubbling stops and only clean fluid is flowing, the brake line is free of air and contaminants. It’s important to maintain the fluid level in the master cylinder reservoir throughout this process to avoid introducing new air into the system. Repeat the bleeding procedure for each brake line, following the established order to ensure all lines are thoroughly flushed.

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Close and Move On

After successfully bleeding each brake line, tighten the bleeder valves securely using your wrench. Remove the tubing and carefully dispose of the old brake fluid, as it is toxic and harmful to the environment. Double-check the master cylinder reservoir to ensure it remains full, topping it off if necessary. Reattach any components you may have removed, such as the tires, and lower your vehicle back to the ground. Taking these final steps ensures that your brake system is clean, efficient, and ready for safe driving.

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Proper Fluid Disposal

Properly disposing of old brake fluid is crucial to protect the environment and comply with local regulations. Do not pour brake fluid down the drain or throw it in the trash. Instead, take the used fluid to a local automotive parts store or a recycling center that accepts hazardous materials. Many communities have designated facilities for disposing of automotive fluids safely, ensuring that they do not contaminate water sources or soil. Responsible disposal helps maintain a clean and safe environment for everyone.

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