Login or Register. Your Z4's pump will almost certainly fail someday unless your car has almost never seen rain. It is attached to the roof assembly which sits inside a compartment that rain seeps into. The compartment has a drain but it's usually clogged so it fills up with water. The water then seeps into a plastic case, which contains your motor and pump, which has a foam lining to reduce the sound of the motor. Once that happens your motor is doomed because the foam absorbs water and it will probably never dry out.