The water pump is a key component to the Ford Focus' cooling system, as it delivers the coolant. A bad water pump will cause the engine to overheat and needs to be changed. The pump itself is powered by the engine's main drive belt. The exact method of removing and installing the pump can vary depending on the year of the car and the engine.
Disconnect the car's negative battery cable, then rase the car's front end and support it on jack stands. Unbolt and remove the lower cover on the auxiliary drive belt.
Drain the cooling system--place a large container under the radiator drain fitting and loosen the fitting, then drain the remaining coolant at the engine block's drain fitting.
Loosen the bolts for the water pump pulley with a wrench but don't remove them yet.
Take off the auxiliary drive belt by rotating the tensioner with a ratchet or breaker bar and socket on the tensioner's center bolt to loosen the tension.
Unscrew and remove the bolts for the water pump pulley and remove the pulley.
Disconnect the coolant hose connected to the water pump housing, then remove the pump's mounting bolts to remove the pulley. Discard the gasket.
Clean off the mating surfaces for the water pump housing using acetone or lacquer thinner.
Install the water pump within the housing and tighten the bolts. If the water pump requires an O-ring, use a new ring and lubricate it with clean engine coolant.
Re-connect the coolant hose to the pump housing and connect the water pump pulley.
Re-install the drive belt using the same method of loosening the belt tensioner.
Refill the radiator and cooling system. Don't use the old coolant if it is dirty; use a fresh mix of antifreeze and water.
Lower the car and re-connect the battery cable.
