BMW Cars 1999-06

Master Cylinder

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Fluid Recommendations & Fill



Use only high quality, name brand DOT 4 brake fluid. Use tightly sealed small containers to refill the reservoir. Large containers offer a false economy. A large container that has been opened will absorb moisture and ruin the fluid. Only use large containers when performing major work on the brake or clutch hydraulic systems and the entire contents will be used at once.

Tightly cap any container to prevent moisture from being absorbed into the brake fluid.

Removal & Installation





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Fig. Cross-sectional view of a tandem master cylinder



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Fig. The fluid reservoir is installed directly onto the brake master cylinder



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Fig. Use a line wrench when loosening or tightening a brake line flare nut for the master cylinder


NOTE
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.

  1. Remove the brake fluid from the reservoir using a siphon or clean baster-type tool. If equipped, disconnect the clutch hose from the reservoir. The clutch hose may have a crimped clamp securing it to the reservoir. Insert a small flat blade prytool through the opening on the side of the clamp and move the screwdriver side-to-side to open the clamp, then slide the clamp toward the reservoir and ease the off the hose. Clean all the brake line connections.
  2.  
  3. If equipped, remove the reservoir-to-master cylinder mounting fastener from the right side (engine side) of the master cylinder, then carefully remove the reservoir from the master cylinder. A trim panel removal tool works well to help remove the reservoir spigots from the master cylinder O-rings. On the E36 models, turn the ignition switch OFF and detach the harness connectors next to the master cylinder to gain more working room.
  4.  
  5. Using a line or flare wrench, remove the line connections from the master cylinder. Plug the lines to avoid contamination from debris.
  6.  
  7. Remove the mounting nuts and remove the master cylinder from the booster, taking care to no lose the O-ring.
  8.  

To install:

  1. Check the condition of the O-ring at the mounting flange of the master cylinder. Clean the mounting surfaces.
  2.  
  3. Install the master cylinder and torque the nuts to 14.5 ft. lbs. (20 Nm).
  4.  
  5. Install the brake lines and torque the connections to 10 ft. lbs. (14.2 Nm). Connect the harness connectors on the E36 models.
  6.  
  7. Thoroughly clean the reservoir with brake cleaner or isopropyl alcohol, then lubricate the spigots and O-rings with a light coating of clean brake fluid and install the reservoir. If equipped, install the clutch hose and secure with a new clamp. Fill the reservoir with fresh and an approved brake fluid and bleed the system as outlined in this section.
  8.  

  1. Disconnect the negative battery cable. Draw off the brake fluid from the reservoir.
  2.  
  3. Remove the plug and disconnect the hydraulic lines. Remove the hose for the hydraulic clutch, if needed.
  4.  
  5. Remove the reservoir. Remove the mounting bolts and lift out the master cylinder.
  6.  

To install:

  1. Install the master cylinder, making sure the rubber ring is making a good seal.
  2.  
  3. Install the reservoir.
  4.  
  5. Attach the brake system hydraulic lines to the master cylinder. Also install the hydraulic clutch line, if removed.
  6.  
  7. Bleed the brake system and connect the negative battery cable.
  8.  

 
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