Master Cylinder: Removal

Suck brake fluid out of expansion tank with a suction device used exclusively for drawing off brake fluid.
Remove brake fluid expansion tank. See BRAKE EXPANSION TANK .
Disconnect all hydraulic lines from master cylinder. Close off brake lines and master brake cylinder using appropriate seal plugs. See Fig 1.
Remove master cylinder-to-power booster nuts. Remove support and master cylinder.
Replace O-ring. See Fig 2.

Fig 1: Locating Screw Connections

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Locating O-Ring

Courtesy of BMW OF NORTH AMERICA, INC.