The Stewart Components Performance Water Pump is absolutely the best water pump ever produced for a BMW car. Stewart Components is the leading producer of water pumps for NASCAR, Ford, and Chevy V-8 domestic race cars, as well as many newer electric OEM applications from BMW and Mercedes.
The unique Stewart Water Pump solves many problems associated with the stock design and later aftermarket evolutions, and it introduces impressive performance and durability features:
15% flow increase
Twice as efficient as a factory pump
Stainless steel impeller
Silicon carbide and sintered carbon graphite seal
The initial factory plastic impeller water pump design was lightweight and provided adequate flow for low RPM use, but it would eventually crack and fail. Later designs used a heavier metal impeller that proved to be very hard on the bearings in the unit. Stewart has used a proprietary impeller that reduces strain on the bearings and seals in the water pump unit, which means greater life for the bearings. Additionally, an oversized FAG bearing and high-quality seal ensure long life.
The Stewart Water Pump impeller design allows for more fluid to be pumped at any given RPM. At high RPM it eliminates cavitation of the pump completely, which means more cooling for your car, completely eliminating the elevated temps seen by many on the track. Racers will be able to further underdrive this pump for even less less power loss.
Fits all E36 6-cylinder cars (1992-1999 323, 325, 328, and M3), E46 non-M cars (323, 325, 328, 330), and all Z3 and Z4 models.