Trucks that run on gasoline have engines that are water cooled. The engine block is designed with channels that coolant passes through. The coolant absorbs the heat from the engine and dissipates that heat through the radiator. This process happens continuously as the engine runs. The hot coolant can also be diverted to the heater core. The heater core works like a radiator by heating the air around it, the hot air is trapped in duct work and blown into the cab of the truck. For all of this to work correctly, the coolant must be circulated through the system, that is the job of the water pump.
The water pump bolts onto the front of the engine and is driven by the fan belt or serpentine belt. The belt turns a shaft that has an impeller attached. The impeller looks like a fan with many blades. The blades trap and push coolant as they turn. The impeller pulls coolant from the bottom radiator hose and forces the coolant into the engine block. As long as the engine is running, the impeller is turning. Some trucks have a diverter hose that attaches to the output side of the pump; this hose will bring coolant to another part of the engine that needs it.
Water pumps are designed to drip from a hole in their case before they fail. The hole is known as the weep hole and is located beneath the impeller shaft. The only part of the water pump that can fail is the bushing that the impeller shaft passes through. The bushing helps the shaft spin freely, but over time the bushing will wear out. If coolant cannot flow through the engine, it will eventually overheat. The excessive heat that builds up can cause several problems, such as weak or broken hoses and warped or seized engine parts.
Replacing a water pump on a truck requires removing the lower radiator hose, the fan and the fan or serpentine belt. The pump is secured with several bolts; removing them can be a difficult job if the mounting bolts have corroded. Be prepared to replace the gasket that seals the water pump to the engine. Using an old gasket, or failure to install a gasket, will cause the pump to leak coolant.
