FixVault

Master Cylinder with Reservoir

The tandem master cylinder is available in two versions one for ABS/ASC and one for DSC, both have a piston diameter of 22.2 mm. The visible difference between the two units is the single sensor fitted to the underside of the master cylinder on the DSC unit. This sensor informs the DSC control unit whether the driver has applied the brakes during DSC intervention.

Fig 1: Master Cylinder/Brake Booster (Non DSC)
G04725151Courtesy of BMW OF NORTH AMERICA, INC.
Fig 2: Master Cylinder/Brake Booster (DSC)
G04725152Courtesy of BMW OF NORTH AMERICA, INC.

The reservoir is secured to the master cylinder by a bolt connecting two mounting tabs. A sensor monitors fluid level, and supplies information to the ABS/DSC control unit. Two "O" rings seal the unit to the master cylinder. The reservoir also supplies fluid to the clutch hydraulics on manual gearbox models. There is an integral filter in the filler neck to prevent dirt contamination of the fluid.