The purpose of a car water pump is to push coolant through the car's engine block, radiator and hoses to get the engine heat away from the system. Most frequently, the water pump drives off the crankshaft pulley or the crankshaft itself. The coolant that gathers between the impeller blades travels outward using centrifugal force, and suction draws the coolant into the water pump from the radiator.
After the coolant enters the water pump, it goes through the whole engine, where it absorbs the heat that the combustion process produces, and then it goes to the radiator, so the heat can exit to the outside air. If the car's water pump is at not working, the most common reasons come from contamination in the fluid, high levels of vibration or a lack of balance in the load. Fluid contamination often brings abrasive items in contact with he pump, leading the shaft seal to fail prematurely. Loads that are out of balance or excess vibration can come from mounting bolts that are loose or incorrectly torqued, distorted or bent pulleys or a fouled mounted fan assembly. When failures come from a lack of balance or vibration, the result can be a shaft failure, which can wreak considerable damage on the components around it.