How To Bleed Brakes

Your car brakes operate using a hydraulic system, which uses brake fluid to transfer the force applied by your foot to the brakes.

However, this system relies on the fluid having no air in it. Like all fluids, brake fluid cannot be compressed, but air can be. If air becomes present in the fluid, then the effectiveness of the braking force being applied will be reduced. So, bleeding car brakes is the process of removing any air bubbles from the brake fluid to improve your braking ability and make your brakes feel more responsive. It’s also used for replacing the brake fluid at the recommended manufacturer intervals.

There are a few key signs to look out for that may indicate that there’s excess air in your braking system:

• Your brake pedal feels spongy or soft when applied
• Your brake pedal can have a longer than normal travel
• It takes longer to come to a stop
• You need to pump the brakes in order to stop

You should also bleed your brakes if:

• You’ve replaced a hydraulic component of the braking system such as a wheel cylinder or flexible brake hose
• It’s been two years since you last bled your brakes

You may want to consider changing your brake fluid when replacing your brake pads, discs, or any other braking components too.

If your car has ABS brakes (anti-lock brakes), then you may not be able to follow the steps in this guide. Bleeding an ABS system can involve a specialized scan tool that removes any air that has gotten into the ABS module.

If your car has an anti-lock system and you think the brakes need to be bled, we can help. Book in for a Free Brake Check at your local Halfords garage, where one of our experts will assess the health of your braking system to understand what’s going on. From there, we can advise you on any next steps.

• Safety gloves
• A jack and axle stands – this is essential if you need to raise the car and will make it easier to access the bleed nipples
• Brake fluid that’s compatible with your car
• A spanner that fits your car’s bleed nipples
• Penetrating fluid
• A container to hold the old brake fluid and length of clear tubing that fits snuggly over the bleed nipples – you can also purchase a brake bleeding kit with these items
• Newspaper or a floor covering to catch any leaks
• Another person – this process is much easier with a helper, so we recommend having someone else stay in the driver’s seat to pump the brake pedal while you release and close the bleed nipples

Note: The engine should not be running while carrying out a brake fluid change unless required by the manufacturer.

You should start with the brake that’s furthest away from the master cylinder, working your way round the car to end with the brake closest to the cylinder. This stops any air re-contaminating the brakes you’ve already bled. Some cars may differ, so check your owner’s manual for more guidance on what order to bleed your brakes.

Locate the master cylinder (usually under the bonnet).

Fill it to the max mark before you begin, and keep it topped up throughout the process.

Locate the bleed nipples, usually found on the brake calliper or wheel cylinder.

Using your spanner, loosen the nipple slightly, but don’t fully turn it.

Push the tubing over the bleed nipple– it should be fitted securely to stop any leaks.

Put the other end of the tubing into the container, ready to catch the fluid.

Slacken the bleed nipple. Be careful, as they can break easily.

Spray some penetrating fluid to help release the bleed nipple if needed.

Have your helper slowly depress the pedal until brake fluid (and possibly some air bubbles) come out through the clear tube.

Note: The person applying the brake should feel the pedal sink to the floor. Don’t panic - this is normal.

Have your helper hold the pedal to the floor. When fluid stops coming out, close the bleed nipple.

Once the bleed nipple is shut, release the brake pedal.

Don’t release the brake pedal while the nipple is open, as air will be sucked back into the brake line.

Repeat steps 4-6 until the brake fluid in the tube is clear, with no air bubble.

If you’re struggling to get the air out, open the bleed nipple and have your helper pump the brakes a few times before holding the pedal down.

Once the first brake has been bled, repeat the process around the rest of the car. Top up the brake fluid reservoir regularly.

Once all four brakes have been bled, make sure the bleed nipples are closed properly.

Note: We recommend bleeding all four brakes at the same time, to make sure that there’s no air in the system.

Try pressing your brake pedal. If it still feels spongy, repeat this process.

If the brakes feel firmer, then you’ve successfully bled the air from the system.