Bleed Car and Motorcycle Brakes

Sometimes air gets trapped in your vehicle's brake lines. Trapped air can make your brakes feel "squishy" or "soft", and too much air in your braking system can cause brake failure. To restore the responsiveness of your brakes, you need to bleed the air from your brake lines. To bleed your brakes follow these simple instructions to do it yourself and save some money.

Steps

Car Brakes

Prepare the Car

  1. Park your car on a flat surface. Automatic transmission cars should be in “park” and standard transmission cars should be in first gear.
    • Please find a safe location, away from traffic, to park your car as you work.
  2. Remove the wheels. To gain access to the brake lines you will need to remove all four of your car's wheels. To do this raise the car on four jack stands, remove the hubcaps, loosen the lug nuts and remove all four wheels.
  3. Find the brake fluid reservoir. The brake fluid reservoir or master cylinder reservoir is located under the car hood. To find the brake fluid reservoir open the hood and locate a small container - usually light colored with a black cap - on the driver’s side of the car. This is the brake fluid reservoir
  4. Clean the reservoir. To clean the brake fluid reservoir, first remove any old brake fluid from the reservoir. To do this, remove the reservoir's lid and use a turkey baster (or similar siphoning system) to remove all of the old brake fluid from the reservoir. When the reservoir is empty, use a clean cloth to remove any sediment from the interior of the reservoir.
    • Be very careful that you do not spill any brake fluid on your car's painted surfaces, as brake fluid will damage your paint.
    • Dirt particles can contaminate brake fluid and cause brakes to fail. This is why it is important to clean out the reservoir.
    • If you find upon opening the brake fluid reservoir that the brake fluid is low, you likely have a leak in your brake lines. The brake system is a closed system and you should not lose brake fluid over time [1]. This problem should be addressed by professionals.
  5. Refill the reservoir with new, clean brake fluid. Once the reservoir is clean, refill it with new brake fluid to the fill line. When filled, replace the lid of the brake fluid reservoir.
  6. Pump your brakes. Pump your brakes (press your brake pedal down) 15 or more times. This will work down the clean brake fluid.
  7. Loosen the bleeder valves. Locate the bleeder valves, near where the tires once were. Wipe off any debris from the bleeder valves and loosen their caps using a box-end wrench.
    • You may need to use penetrating oil (WD-40) to loosen the bleeder valve caps.

Bleed the Car Brakes

  1. Attach the tubing. Start with the brakes furthest from the brake cylinder, usually the back right brakes. Locate the brake line's bleed screw and slide one end of the clear tubing over the nipple on the bleed screw. Submerse the other end of the tubing into a few inches of clean brake fluid in a disposable container.
    • You want to submerse the tubing in clean brake fluid to prevent air from being sucked up into the braking system.
  2. Depress the brake. Get a helper to slowly and evenly press the brake pedal to the floor and hold it down. The helper should signal "down", as they continue to hold the pedal down [2].
  3. Open the bleeder bolt. While your helper is holding down the brake pedal, open the brake lines by turning the bleeder bolt a quarter turn. When you do this old brake fluid will travel down the tubing into the waste bottle. As this happens the brake pedal will settle further down under your helper's foot.
    • Failure to hold the brake down while the bleeder bolt is open, will suck air into the brake system [2]. Do not do this. Make sure that the brake pedal is down when any bleeder bolts are open.
  4. Close the bleeder bolt. When fluid stops flowing, close back up the bleeder valve. Only after the bolt is closed again should the helper release the brake pedal.
  5. Release the brake. After the bleeder bolt is closed again, signal to the helper to release the brake.
  6. Repeat 10-15 times. Repeat the steps, "Depress the brake", "Open the bleeder bolt", "Close the bleeder bolt", "Release the brake" on the same brake line until the brake fluid runs clean. This may take 10-15 repeats. After the brake fluid runs clean, close the bleeder bolt for a final time.
    • After every five repeats make sure to top off the brake fluid reservoir. This is important, otherwise you risk sucking air into your brake system.
  7. Repeat for the other wheels. Repeat the "Bleed the Car Brakes" section on the other three brake lines, left-rear, right-front and left-front, until the brake fluid runs clean.

Test the Car Brakes

  1. Clean up any spills. Make sure no brake fluid has spilled on the rotors or brake pads. If any has spilled, use brake cleaning spray to remove it.
  2. Replace the wheels. Replace all four wheels and hand-tighten the lug nuts. Engage the parking brake. Lower the vehicle to the ground and tighten the lug nuts. Replace the hub caps if present.
  3. Test the brakes. Tap the brake pedal a few times without the motor running until all the slack in the line is removed. Go for a slow test drive to see if the brakes are functioning correctly before going for a long drive.

Motorcycle Brakes

  1. Prepare your bike. The night before, clean around your bike's bleed screws. You may need to spray your bleed caps with WD-40 to loosen them.
  2. Position you bike. Park your bike in a flat, safe place. Turn your bike's front wheel into the position needed to make the brake fluid reservoir, also known as the master cylinder, level. Lock your wheel into position.
    • Make sure you find a safe location to park your bike as you work, away from traffic.
  3. Set brake levers. If your brake levers are adjustable, set them at their most open setting [3].
  4. Remove caps and covers. Remove the rubber caps from the bleed screws[3]. Remove the brake fluid reservoir's cover to expose the brake fluid[3].
  5. Clean the reservoir. Using a turkey baster or similar siphoning system remove all of the old brake fluid from the reservoir. When empty, use a clean cloth to remove any sediment from the interior of the reservoir.
    • Be very careful that you do not spill any brake fluid on your bike's painted surfaces, as it can damage your paint.
    • Dirt particles can contaminate brake fluid and cause brakes to fail.
    • If you find that the brake fluid is low upon opening the brake fluid reservoir, you have a leak. The brake system is a closed system and you should not lose brake fluid over time [1]. If you have low brake fluid, the leak needs to be addressed by a professional to insure safe riding.
  6. Refill the reservoir with clean brake fluid. Once the reservoir is clean, refill it with new brake fluid to the fill line.

Vacuum Pump Method of Bleeding Brakes

  1. Attach the vacuum hoses [3]. Attach the first vacuum hose from a bleed screw to the pump bottle using an adapter as needed. Attach the second vacuum hose from the bottle to the vacuum pump.
  2. Vacuum out brake fluid. Squeeze the pump handle until the pressure registers between 10 and 20 mmHg [3]. While under pressure, loosen the bleed screw a quarter turn. Fluid should be seen filling the bottle.
    • Tighten/loosen the screw for an even, controlled flow. If the bleed screw is too loose the fluid will flow too rapidly and air will get into the system.
  3. Keep reservoir full. As the brake fluid drains, you will notice the brake fluid level in the brake fluid reservoir falling [3]. Continue to pour new brake fluid into the brake fluid reservoir to maintain the fluid level. If you do not maintain the brake fluid in the reservoir air will enter the braking system.
  4. Stop. When there are no air bubbles visible in the hose and the brake fluid runs clean, you are done. Tighten the bleed screw, before turning off the vacuum [3].
  5. Repeat on other caliper. Repeat the steps "Attach the vacuum hoses", "Vacuum out brake fluid", "Keep reservoir full", "Stop" on the alternate side caliper.
  6. Repeat on other tire. Repeat steps "Vacuum Pump Method" section on other tire's brake lines.

Press & Hold Method of Bleeding Brakes

  1. Attach the tubing. Slide one end of the clear tubing over the nipple on a bleed screw. Submerse the other end of the tubing into a few inches of clean brake fluid in a disposable container (an old water bottle works).
    • You want to submerse the tubing in clean brake fluid to prevent air from being sucked up into the braking system.
  2. Pump the brakes [3]. Pump the brake lever about five times.
  3. Hold the brake and drain. Hold the brake lever down with one hand, and open the bleed screw with a box wrench with your other hand. This will allow old brake fluid to flow into the catch bottle [3].
  4. Close the bleed screw, then release brake. Only after closing the screw are you safe to release the brake. If you release the brake while the screw is open you will suck air into your braking system.
  5. Repeat ~five times [3]. Repeat the steps "Pump the brakes", "Hold the brake and drain", "Close the bleed screw, then release brake" at least five times.
    • While repeating this process make sure to regularly check the fluid level in the brake fluid reservoir. If you do not keep the reservoir full, air will enter the braking system through the empty reservoir. Add brake fluid as needed to keep it full.
    • Repeat this process at least 5 times. Repeat until the brakes feel solid, if you just want to bleed the brakes; or until the brake fluid run cleans, if you want to replace the fluid.
  6. Repeat the "Press & Hold Method" on the alternate side caliper.
  7. Repeat the "Press & Hold Method" for each caliper on the other wheel.

Test Your Brakes

  1. Finish. When satisfied, make sure the expansion gasket on the reservoir is clean and close the topped-off reservoir. Press the gasket into place. Remove the catch bottle and tubing, and replace the rubber caps over the bleed screws [3].
  2. Clean up any spills. Make sure no brake fluid has spilled. If any has spilled, use brake cleaning spray to remove it.
  3. Test the brakes. Squeeze the brakes a few times without the motor running until all the slack in the line is removed. Then go for a slow test ride to see if the brakes are functioning correctly before going for a long ride.

Tips

  • Only use the brake fluid recommended for your vehicle.
  • Avoid brake fluid coming in contact with rubber, plastic or paint.
  • Do not release the brakes until the bleeder screws are all closed.
  • Bleed your vehicle’s brake lines every two years.
  • Properly dispose of waste brake fluid.
  • Note that not all rear brakes are hydraulic (i.e., use brake fluid). These steps may not apply to your rear brakes.
  • Be careful when jacking up a vehicle.

Warnings

  • The advice found in this article is general advice. Be sure to consult your car's or motorcycle's manual for specific instructions regarding bleeding your brakes.

Things You'll Need

Car Brakes

  • Jack stands (4)
  • Suction tool, such as a turkey baster
  • Box Wrench
  • Brake fluid
  • Brake cleaner
  • Clear plastic tubing
  • Disposable waste container (old water bottle works well)
  • Soft clean cloths
  • WD-40

Motorcycle Brakes

  • Suction tool, such as a turkey baster
  • Box Wrench
  • Brake fluid
  • Brake cleaner
  • Clear plastic tubing
  • Disposable waste container (old water bottle works well)
  • Soft clean cloths
  • Vacuum (if using that approach)
  • WD-40

Related Articles

References

  1. ↑ 1.0 1.1 http://auto.howstuffworks.com/auto-parts/brakes/brake-repair/brake-bleeding.htm
  2. ↑ 2.0 2.1 http://www.popularmechanics.com/cars/how-to/maintenance/4213448
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 http://www.ebay.com/gds/How-to-Bleed-Motorcycle-Brakes/28549/g.html
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