Hummer owners put their engines through a lot of wear and tear - and accordingly, the Hummer water pump will be vulnerable to deterioration that comes from so much demand put on the engine. The Hummer water pump's job is to move coolant fluid through the cooling system. The Hummer pump relies on a belt that is hooked up to the crankshaft of the engine. The pump circulates fluid when the engine is running. The pump is designed as a rotary dynamic (centrifugal) pump. In those kinds of pumps, the impeller part forces the coolant fluid to rotate. Under that force, the fluid moves around under its own momentum. Remember your old physics in high school? The power of the pump's centrifugal force sends the water out of the pump while it spins, while the fluid is continuously drawn from the center. The Hummer water pump sends the fluid through the engine like this: the fluid returns from the radiator and hits the pump vanes. Then, the pump vanes move the water outside of the pump to the engine. In the engine, the fluid flows to the engine block, cylinder head and radiator. Finally, the fluid ends up back at the pump. On average, your water pump can be expected to fail sometime before 100,000 miles on your car, or sooner. If you suspect your Hummer water pump is starting to fail, replace it now and avoid major headaches and repair bills down the road.