DIY

How to Bleed Brakes

Reading Time: 5 minutes

Whenever you service the hydraulic portion of your car’s brake system, you must bleed the brakes afterward. Failing to do so will result in little to no braking ability—and that can make for a really bad day. 

You can choose to bleed the brakes by yourself (with the proper equipment), or you can tackle the job with the help of an assistant. Regardless of which method you choose, you must get all of the air out of the brake system before driving the vehicle. 

How Do You Bleed Brakes? 

Opening the hydraulic portion of the brake system introduces air into the brake lines. While air is compressible, brake fluid (like any other type of liquid) is not. Brake fluid that’s full of air reduces the force the hydraulic system creates, resulting in a dangerously spongy brake pedal. 

Bleeding brakes used to be a straightforward affair that was virtually the same on all vehicles. But now, there are instances where the bleeding procedure is complex enough to require a scan tool.  

Because of this, it’s a good idea to consult the appropriate service information before attempting to bleed the brakes. Repair manuals, such as those from Chilton, are good, but a subscription to a repair database (e.g., ALLDATA or Mitchell 1 DIY) is even better. You can find more information on accessing quality repair information in our article on repair manuals.

hose connected to brake for bleeding brakes

5 Methods for Bleeding Brakes

With that out of the way, let’s discuss the primary methods for bleeding brakes.

Manual Bleeding

The bleeder valve is opened and closed while an assistant manually operates the brake pedal. 

Vacuum Bleeding

Uses a special vacuum pump to pull brake fluid through the open bleeder valve. 

Gravity Bleeding

Allows gravity to slowly pull brake fluid through the open bleeder valves.

Pressure Bleeding

Uses a special pressure bleeder tool to force air out through the open brake bleeder.

Reverse Flow Bleeding

Uses a special injector tool to force air through the bleeder valve, into the brake system, and out through the fluid reservoir.  

Most DIYers choose the manual bleeding method because it doesn’t require a special tool, and it’s much quicker than the gravity bleeding option. 

How to Bleed Brakes (Using the Manual Bleeding Method)

The manual brake bleeding method requires the following tools and equipment: 

  • An assistant 
  • An appropriate-size line wrench
  • A length of clear plastic hose that fits snuggly over the bleeder screw
  • An old plastic water bottle partially filled with brake fluid  
  • Brake fluid 

Here are the general guidelines for manual brake bleeding: 

Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.  

  1. Ensure that the master cylinder is full of fluid. 

  2. Determine the correct bleeding sequence. Consulting a repair manual or a repair database is the best way to determine the bleeding sequence for your vehicle. But there’s also a rule-of-thumb method, which is to start at the wheel with the longest brake line attached. In most cases, that’s the wheel farthest from the master cylinder (i.e., the right rear).

    Note: The engine should be off while performing this procedure. 

  3. Attach a rubber hose to the end of the first bleeder screw in the sequence. Make sure the hose fits snugly over the screw’s nipple. 

  4. Submerge the other end of the hose in a clear container (such as an old water bottle) partially filled with brake fluid.

  5. Have your assistant put their foot on the brake pedal and apply light pressure. 

  6. Use a line wrench to crack open (about 1/4 turn) the first bleeder screw in the sequence. Do not remove the bleeder screw. 

  7. Tell your assistant that you have the bleeder open, then have them slowly depress the brake pedal. Instruct them to tell you when the brake pedal is getting close to the floor. 

  8. Allow fluid to run from the bleeder screw into the container. Watch for air bubbles flowing through the clear plastic hose. 

  9. When fluid stops flowing (or your assistant tells you the pedal is near the floor), close the bleeder.

  10. Tell your assistant that the bleeder is closed. They can now release the brake pedal.

    Note: You’ll want to check the master cylinder fluid level often during this procedure. Air will get sucked back into the system if the master cylinder runs out of fluid.

  11. Repeat the procedure until you no longer see air coming from the bleeder.

  12. Move to the next corner of the vehicle and repeat the bleeding procedure until you’ve covered all four wheels.

  13. Once the entire system has been bled, check the feel of the brake pedal. It should be firm. If not, continue to bleed the brakes until pedal feel is satisfactory.

The video below provides a visual representation of the manual brake bleeding process: 

How to Bleed Brakes By Yourself (Using the Vacuum Bleeding Method)

You can use the vacuum, pressure, gravity, or reverse flow bleeding methods to bleed the brakes by yourself. But most DIYers choose the vacuum bleeding method because vacuum pumps are relatively affordable. Plus, vacuum bleeding is much quicker than gravity bleeding. 

The vacuum brake bleeding method requires the following tools and equipment: 

Here are the general guidelines for vacuum brake bleeding: 

  1. Ensure that the master cylinder is full of fluid. 

  2. Determine the correct bleeding sequence. Consulting a repair manual or a repair database is the best way to determine the bleeding sequence for your vehicle. But there’s also a rule-of-thumb method, which is to start at the wheel with the longest brake line attached. In most cases, that’s the wheel farthest from the master cylinder (i.e., the right rear). 

    Note: The engine should be off while performing this procedure. 

  3. Attach the hose from the vacuum pump to the first bleeder screw in the sequence. Make sure the end of the hose fits snugly over the screw’s nipple. 

  4. Use a line wrench to crack open (about 1/4 turn) the first bleeder screw in the sequence. Do not remove the bleeder screw. 

  5. Operate the bleeder pump and note the flow of fluid through the tool’s hose. 

  6. Once the rate of air bubbles flowing through the hose begins to drop, close the bleeder screw. 

    Note: You’ll want to check the master cylinder fluid level often during this procedure. Air will get sucked back into the system if the master cylinder runs out of fluid.

  7. Move to the next corner of the vehicle and repeat the bleeding procedure until you’ve covered all four wheels.

  8. Once the entire system has been bled, check the feel of the brake pedal. It should be firm. If not, continue to bleed the brakes until pedal feel is satisfactory.

The video below provides a visual representation of the vacuum brake bleeding process: 

Some people also claim to have success bleeding the system manually by themselves. Here is a video demonstrating that method: 


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Author

Mia Bevacqua

Chief Mechanic at CarParts.com

Mia Bevacqua is an automotive expert with over 15 years of industry experience. She holds ASE Master, L1, L2, and L3 Advanced Level Specialist certification, as well as a bachelor's degree in Advanced Automotive Systems.

Throughout her career, Mia has applied her skills toward automotive failure analysis inspections, consulting, diagnostic software development, and of course, writing.

Mia has a passion for math, science, and technology that motivates her to stay on top of the latest industry trends, such as electric vehicles and autonomous systems. At the same time, she has a weakness for fixer-upper oddballs, such as her 1987 Chevy Cavalier Z-24 and 1998 Chevy Astro Van AWD.

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