For establishing an adequate engine vacuum to the brake vacuum booster at all engine speeds, there is an induction driven vacuum pump fitted to the engine, located beneath the intake manifold on the front left side. BMW has indicated that the sprocket center bolt must be loosened while the sprocket is immobilized which is best done by use of BMW special tools. First take out the engine drive belt followed by the drive belt tensioner assembly. Loosen the sealing cover for the vacuum pump with the help of a screwdriver from the front side of the engine so as to reach the sprocket. Second, take away the intake manifold. For normal direction of engine rotation turn the center bolt of the vibration damper until the holes in the sprocket match the position of the pump bolts. Mount BMW special tool 114362 to the engine and engage the sprocket with the engine and secure it by using BMW special tool ref 110290. Loosen the sprocket mounting bolt and later on the pump mounting screws, and ensure that the pump does not drop. Last but not the least, pull out the vacuum pump toward the rear, and while installing it, just reverse the above-stated procedure and install the gasket.