The circulating power of the BMW Water Pump is what keeps your engine at the correct operating temperature. This coolant component is located on the center front section of the engine. The water pump draws the coolant from the radiator through the lower coolant hose. The outlet of the BMW water pump is directly into the engine block.
The part that fails on the water pump is the polymer seal on the impellor shaft where it protrudes from the housing unit. This shaft has the pulley at the exterior end where it receives the centrifugal power from the drive belt system on your BMW. When this seal is breached, coolant will begin to leak out of the small hole in the bottom of the water pump.
If the ruptured seal is ignored for too great of a time, then not only will the coolant continue to flow out of the system, but the shaft on which the seal is on can begin to wobble. It is not unheard of for those models of BMW with the radiator fan at the end of this shaft to become so lose that the fan becomes lodged in the radiator.
The replacement of the water pump is not a complicated procedure and can be accomplished by the owner of the BMW. The most difficult and time consuming portion of this repair procedure is actually gaining access to the pump by removing the drive belt system and components. Once this is accomplished, the engine block can be scraped of the old gasket material and the new pump put into place. If any of the old gasket material is left on the engine block, a good seal will not be possible and a new leak will occur require the repair job to be redone correctly.