BMW Cars 1999-06

Bleeding the ABS System

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WARNING
If the vehicle is equipped with ASC+T, the BMW Service Tester must be used to properly bleed the system. Due to safety and liability issues, this job should only be performed by a BMW dealer.

While parts of the of the ABS system can be removed and replaced by the owner of the vehicle, special tool, technique and procedure are needed to check the operation and performance of the system once repairs are completed.

To bleed the hydraulic system, a necessary step after the hydraulic system has been repaired, the BMW Diagnostic Tester or equivalent must be utilized to electronically open the internal valve. Only this way can the system be completely bled.

To check the operation of the ABS system after any of the electronic portions have been replaced or disconnected, the BMW Diagnostic Tester or equivalent must be used.

It is recommended to allow a licensed and trained professional to complete repairs on the ABS system. Most repairs are straightforward, but the diagnosis and testing of the system can enter a different realm. The safety and integrity of the braking system must never be compromised.

To ensure continued proper operation of the braking system, the brake fluid must be changed at least every 2 years. If the vehicle is used for heavy duty use, change the fluid at least once a year. If the vehicle is used in competition or drivers schools, bleed the system before and after each event or at least every 90 days.

Use a quality, approved DOT 4 brake fluid. Use fluid from sealed, unused cans. Buy the fluid in quantities that you expect to use. Buying a large container of fluid and only using a small portion can lead to the remaining fluid to become contaminated over time. Brake fluid absorbs moisture and can lead to system corrosion.


NOTE
Always use a fresh, clean, factory approved brake fluid.


WARNING
This procedure is only valid for vehicles without ASC+T. If the special procedures are not performed in accordance to BMW requirements, the brake system may not function properly possibly resulting in severe personal injury.


NOTE
Brake caliper bleed screws have a tendency to seize in the caliper body. If seized, spray the bleed screw with a penetrating lubricant. Place a properly fitting deep well, 6 point socket on the bleed screw. Use a T-handle driver to turn the socket, apply equalized rotational pressure to both sides of the T-handle when loosening. This will avoid side loading the bleeder, which due to its relative small size and the fact that it is hollow, the bleeder valve can be easily sheared off. Should this occur, check with your local auto parts vendor for a bleeder valve repair kit. Once the bleeder has been loosened, use a small wrench to open and close the bleeder as necessary while bleeding.

  1. Fill the master cylinder to the maximum level with the proper brake fluid.
  2.  
  3. Attach a pressure bleeder to the master cylinder reservoir. Do not allow the pressure to exceed 29 psi (2 bar).
  4.  


NOTE
An assistant will be needed to properly bleed the brake system.

  1. Raise and safely support the vehicle.
  2.  
  3. Remove the protective caps from the bleeder screws and bleed the brakes using the following bleeding sequence. Always starts with the brake unit farthest from the master cylinder. The proper bleeding sequence is:

    Right rear
     
    Left rear
     
    Right front
     
    Left front.
     

  4.  
  5. Insert a tight fitting clear plastic tube over the bleeder screw on the caliper and the other end of the tube in a transparent container partially filled with clean brake fluid.
  6.  


WARNING
When bleeding do not allow the system to run dry, otherwise the entire procedure must be repeated.

  1. Have the assistant apply pressure to the brake pedal.
    1. Open the bleeder.
    2.  
    3. While the bleeder is opened, have the assistant pump the brake pedal slowly at least 12 times.
    4.  
    5. When the fluid being dispersed is free of all air bubbles, hold the brake pedal down and close the bleeder valve.
    6.  
    7. Slowly release the brake pedal.
    8.  
    9. Check and top off the brake fluid reservoir and pressure bleeder as necessary.
    10.  
    11. Torque the 7mm bleeders to 44 inch lbs. 3.5 ft. lbs. (5 Nm) and the 9mm bleeders to 53 inch lbs. 4.3 ft. lbs. (6 Nm). Replace the bleeder dust covers.
    12.  

  2.  
  3. Repeat the brake bleeding steps above for each caliper in the following order.
    1. Left rear
    2.  
    3. Right front
    4.  
    5. Left front
    6.  

  4.  
  5. Lower the vehicle, check the brake fluid level, top off as necessary and check for normal operation of the brakes.
  6.  



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Fig. Bleeding the front brakes. Replace the bleeder cover when done



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Fig. Bleeding the rear brakes. Replace the bleeder cover when done



Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.



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Fig.

 
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