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Pelican Technical Article:

Brake Bleeding

Nick Czerula

Time:

1 hour1 hr

Tab:

$30

Talent:

**

Tools:

11mm wrench, pressure bleeder

Applicable Models:

BMW 525i/xi Sedan (2004-07)
BMW 528i xDrive Sedan (2009-10)
BMW 528i/xi Sedan (2008-10)
BMW 530i/xi Sedan (2004-07)
BMW 530xi Wagon (2006-07)
BMW 535i xDrive Sedan/Wagon (2009-10)
BMW 535i/xi Sedan (2008-10)
BMW 535xi Wagon (2008)
BMW 545i Sedan (2004-05)
BMW 550i Sedan (2006-10)
BMW M5 Sedan (2006-10)

Parts Required:

Brake fluid and brake cleaner

Hot Tip:

Bleed vehicle twice to ensure all air is removed from system

Performance Gain:

Good brake operation

Complementary Modification:

Replace worn brake parts

When you step on your brake pedal, you are compressing a piston in your brake master cylinder. This cylinder is full of brake fluid. The brake fluid that is now under pressure travels through your brake lines and is finally applied to your caliper. It's the calipers job to squeeze down on the brake pads against the rotor to slow down your car. If you have opened up the system to service it or you just want to flush out the old brake fluid, you should bleed your brakes. When the system is open air gets in. The bleeding process bleeds the air out of the system. If you add new fluid to the master cylinder reservoir as you bleed the brakes the old fluid is forced out and the new fluid is drawn in. BMW recommends you flush out your brake system every two years.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

There are a few ways to bleed brakes. There are pressure bleeders available that apply pressurized brake fluid to the master cylinder reservoir. All you have to do is open a bleeder valve. The new fluid from the pressure bleeder tool is forced into the master cylinder with air pressure. The old fluid is forced out the bleeder screw. Simply open the bleeder until you see cleaner brake fluid come out and then close the bleeder screw. The maximum pressure you want to run through the brake system using a pressure bleeder is 10 PSI. This is the procedure I am describing in this tech article. If you have the aforementioned tools, follow the tool manufacturer's instructions that came with the tool.

There are vacuum bleeders that work on the vacuum principle. There are two types. One is an air powered one that uses shop air pressure to generate a vacuum in the tool. This vacuum source is piped to the bleeder screw. With vacuum applied open the bleeder screw and vacuum will suck out the old fluid until the new fluid from the reservoir comes out then close the bleeder screw. There are manual tools that have you manually pump the tool to generate vacuum. You will have to close the bleeder screw from time to time and pump on the tool to make vacuum then open the bleeder screw again.

The final method does not require any special tools but you will need a helper. Make sure to clean around the brake fluid reservoir cap before removing it, as you do not want to get any dirt into the reservoir. Fill the reservoir with new brake fluid. It is very important that you keep the reservoir full during the brake bleeding procedure. If it runs dry you will allow air to get drawn into the system through the master cylinder and you will have to start all over again. Check the brake fluid level after bleeding each caliper.

The BMW recommended procedure is to bleed the right rear caliper, followed by the left rear wheel, then the right front caliper and finally the left front brake caliper. The reason is that the right rear brake line is the longest. The brake line starts at the master cylinder on the right side, moves across the body to the hydraulic assembly and then to the back of the car to the right rear caliper. The next longest line is the left rear, followed by the right front and the shortest line is the left front.

Install a 11mm wrench on the right rear bleeder screw. Then install a hose to the brake bleeder screw nipple. This helps to keep your wheels clean during the process.

Have your helper step on the brake pedal all the way to the floor and all the way back three full times, then have them hold the pedal firmly to the floor. Open the bleeder screw on the right rear caliper by turning the wrench counterclockwise. If you opened the brake system for service you will probably get air out first. If you are flushing your brake system, watch the flow of the brake fluid in the hose. It should rush out then slow down. Your helper will feel the pedal sink to the floor. Tell them to keep the pedal pushed to the floor. This will prevent air being let back into the caliper. Close the bleeder screw by turning it clockwise. Have your helper pump the brake pedal again three times and hold it to the floor again. Open the bleeder screw again and have your helper continue to force the pedal to the floor. When the fluid stops flowing or the pedal sinks all the way to the floor close the bleeder screw. Look for air bubbles. When you no longer see bubbles move on to the next wheels. Repeat this process. As you bleed out the air in the system your helper will notice the brake pedal getting harder to press and sink more to the floor as you open the valve. This is good. This means you are purging air from the brake hydraulic system. This may take several times to get all the air out. When small air bubbles no longer appear coming out of the caliper you can move on to the next caliper. After each wheel check the fluid level in the brake fluid reservoir and refill it if necessary. Properly tighten all bleeder screws and return any wiring stays and the rubber caps as well. Spray any brake fluid on the vehicle with brake cleaner and let it air dry. Use brake cleaner in a well-ventilated area and let the components air-dry. The brake cleaner will evaporate into the air with time. Make sure the brake fluid reservoir is full and install the cap.

Raise and support the vehicle on jack stands. See our tech article on jacking your vehicle.

Remove the cabin microfilter and microfilter housing (red arrow).
Figure 1

Remove the cabin microfilter and microfilter housing (red arrow). See our tech article on engine covers removing.

Make sure to clean around the brake fluid reservoir cap before removing it, as you do not want to get any dirt into the reservoir.
Figure 2

Make sure to clean around the brake fluid reservoir cap before removing it, as you do not want to get any dirt into the reservoir. Fill the reservoir with new brake fluid. It is very important that you keep the reservoir full during the brake bleeding procedure. If it runs dry you will allow air to get drawn into the system through the master cylinder and you will have to start all over again. Follow the instruction that came with your bleeder.

Then install the pressure bleeder adapter to the brake master cylinder.
Figure 3

Then install the pressure bleeder adapter to the brake master cylinder. Pressurize the brake system to a maximum of 10 psi.

The BMW recommended procedure is to bleed the right rear caliper, followed by the left rear wheel, then the right front caliper and finally the left front brake caliper.
Figure 4

The BMW recommended procedure is to bleed the right rear caliper, followed by the left rear wheel, then the right front caliper and finally the left front brake caliper. The reason is that the right rear brake line is the longest. Install a 11mm wrench on the bleeder screw (blue arrow). Then install a hose (red arrow) to the brake bleeder screw nipple. This helps to keep your wheels clean during the process.

Open the bleeder screw.
Figure 5

Open the bleeder screw. Allow the fluid to run out into a drain pan until no air bubbles are present and clean fluid is being expelled. Once the brake fluid is air-free, close the bleeder and repeat for the left rear wheel. This may take several times to get all the air out. When small air bubbles no longer appear coming out of the caliper, you can move on to the next caliper. After each wheel check the fluid level in the brake fluid reservoir and refill it if necessary. Properly tighten all bleeder screws and return any wiring stays and the rubber caps as well.

Repeat these steps working your way around the vehicle: left rear wheel, right front wheel, and then finally ending with the left front wheel.
Figure 6

Repeat these steps working your way around the vehicle: left rear wheel, right front wheel, and then finally ending with the left front wheel. Be sure the brake fluid reservoir is full and install the cap.




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Comments and Suggestions:
Steven Comments: Okay thanks for the reply. Just to clarify: when you say right you're referring to the right when sitting in the drivers seat of the car correct? So right would be the passenger side of a Left hand drive car
November 16, 2016
  Followup from the Pelican Staff: Yes, right and left when seated in the car facing forward. - Nick at Pelican Parts  
Steven Comments: I have replaced both my master cylinder and brake booster, and I do not have a pressure bleeder so I am doing it the old fashioned way pumping brakes several times with car off, holding pedal while someone cracks the bleeder valve open and pedal sinks, but I am getting tons of air. I've bled through probably 3 bottles of fluid and still getting lots of air.
November 11, 2016
  Followup from the Pelican Staff: Let it gravity bleed for a bit. Do each wheel one at a time, starting at the furthest. Then try bleeding it again. - Nick at Pelican Parts  

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Page last updated: Wed 12/7/2016 02:42:35 AM