What Size Wrench To Bleed Brakes? Brake Bleeding Explained In Full

what size wrench to bleed brakes

Bleeding the brake is the process of removing bubbles present in the hydraulic brake system. The hydraulic brake system is a type of brake mechanism method used for the transmission of energy transferred by the brake oil. On some occasions, you might feel that your brake paddles are not working effectively and have a spongy feeling when pressing the brakes; this can be a sign that you need a bleed brake for your vehicle. To fix the issues, bleeding your brake is vital, and knowing what size wrench to bleed brakes is absolutely pivotal.

The brake fluid is the compressible fluid that and the air is compressible; when the brake paddle is compressed, the air bubble is formed in the hydraulic brake system.

The process of removing the air bubbles through the brake line is known as brake bleeding. However, brake bleeding is not only done when the hydraulic system contains an air bubble; you will also be brake bleeding done while renewing the brake fluid in your car.

Bleeding brakes may not be a major problem in your vehicle, but it is better for your car’s maintenance and safety.

If the brake pads feel spongy before the brake bleeding, it can cause your brake pads to wear off quickly, and bleeding brake to renew brake fluid is helpful for the effectiveness of your brake system.

What Size Wrench To Bleed Brakes

Wrenches, also known as is a type of machine tool that looks is used for screwing, loosening and tightening screws, used for pipes, fittings, etc. wrenches come in different sizes and lengths.

A wrench is needed to remove the screws in the bleed brakes. For that, we need to find out the size of the screw.

Wrenches have usually been used. The wrench size needed to bleed brakes generally depends on the diameter of the bleed brake screws and the head of the wrench.

In most common situations, the standard size wrenches used ¼ inches, 3/8 inches and ½ inches, but to find the size of wrench that you need, you can measure the diameter of the bold and multiply by 1.5.

How To Bleed The Brake?

Bleeding your brake is essential to keep your vehicle in good condition and for your safety. If your brake system is not working, you are not in safe hands and must take the necessary actions to recover the issue in your brake system. Below is the most general way used to bleed brakes in a car.

It is essential to know how to bleed brake in case of emergency,

  1. Before you start anything, adhere to safety rules. Wear a mask and gloves while working with automobile parts in your vehicle.
  2. Fetch the necessary tools, such as the wrencher, nozzle, brake fluid etc.
  3. Use a thick cloth or newspapers when you are crawling under the vehicle
  4. Use a jack to lift the car, so you have enough space to work.

  5. Examine the size of the screw and select the correct wrench that suits the screw. Using the wrench, loosen the screws. If the screws are too hard to loosen, you can use a penetrant or consult a professional to avoid breaking the screw.
  6. Now use a small hose/ line to ensure the hose is flexible. Place the hose at the end of the bleeder screw and the other end on a glass jar.
  7. You will need another person for the next step. You can ask your friend to press the brake paddles a few times. Push the brake paddles slowly and release, press and release. Repeat the process
  8. After finally releasing, push the brake paddle and, from the other end, loosen the tight screws and open them. Your friend must release the pushed paddle for any reason throughout the process, as releasing the paddle cause the brake fluid to suck and return.
  9. Once the brake fluid is removed, you will notice an air bubble in the jar.
  10. Before the brake paddle is released, ensure that you have tightened the screws.
  11. Now release the brake paddles. During the process of pushing and releasing the brake pedal, loosen the screw and tighten them till the air bubbles are completely removed.
  12. Open the master cylinder and pour the brake fluid till the full line
  13. Repeat the same process of bleeding the brakes.
  14. Complete the process when your brake paddle should no longer feel spongy and complete the eradication of air bubbles.
  15. Now you can refill the master cylinder to the full line with brake fluid.

Types of Brake Bleeding

The previously stated method to bleed brake is the most common method used by many, and this method is a two men’s job. However, there are other methods used to bleed brakes, which can be done by yourself without the help of anyone. Below are the types of bleeding brakes explained briefly for common knowledge.

  • Vacuum method – Remove the top of the master cylinder and loosen the cover. Attach a vacuum pump to the bleeder valve and let the brake fluid till you see no air bubbles. Maintain the oil level in the master cylinder
  • Pressure method – To use the pressure method to bleed the brake, you will need a pressure machine, open the master cylinder and using a pressure pump, attach it to the master cylinder. Make sure to keep the brake fluid full during the process. Now open the bleeder valves each time till the air is completely released.


If you feel like your brake paddles are not giving enough pressure to amount of force and feel spongy while pushing the brake pedals, the way to get rid of this is by bleeding brakes. There are different methods to bleed brakes; you must find what is more effective.

To know the exact specifications to what size wrench to bleed brakes cannot be spelt specifically. The size of the screw depends on each type of vehicle and model. But by determining the size of the diameter, you will be able to follow a general chart.

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