the pump circulates the water throught the cooling system. when they fail the engine will overheat... but keep in mind you have other parts that work in conjuction with the pump like the thermostat which opens and closes at certain temps to keep the coolant at the proper working temp so the car runs correclty...if a thermostat fails and is stuck closed you can overheat also or if stuck open then the coolant may run to cool and the car may not run at its best. good luck
Water pumps helps cool down the engine. Without the water the engine will overheat and die.
The water-pump circulates the hot coolant from the engine to the radiator where it is cooled and back to the water-pump through the hot engine again. If you had listed a particular car or truck as an example, some water-pumps push the hottest water in to the radiator through the lower radiator hose where it is cooled and then circulated back through the upper radiator hose to the cylinder-heads first then the block. This is the latest and greatest coolant circulation method because the cylinder-heads are the hottest part of a water-cooled internal combustion engine. The block temperature is always substantially cooler than the cylinder-heads. This is called a reverse cooled cooling system. One of these days to avoid confusion the makers of water-pumps should re-name them simply coolant pumps Race car engines are the only place real pure water is circulated through the cooling systems because antifreeze cuts cooling efficiency.
A water pump pumps a coolant/water mixture through the engine to keep it from overheating. If it breaks, the water can't cool the engine so it overheats.
