This is the water pump and drive layout found on most cars. The pump is mounted on the front of the engine and is driven by a belt which also drives the alternator.
Water pumps wear out through age, through lack of lubrication on older types — which need greasing — or because the drive belt is too tight.
A worn pump may leak around the spindle, in which case there are leak trails down the front of the engine and a slow loss of coolant.
The pump may also rattle as it turns — do not confuse this noise with the screech of a loose, slipping belt.
To check for wear, loosen the belt and, if a mechanical fan is mounted on the pump, grasp opposite blades and try to rock them.
They should not move more than a small amount. If the fan is not fitted directly to the pump, clamp a self-locking wrench on to one of the pump pulley bolts and rock that.
Replace a worn pump. Buy a new gasket too, and some gasket sealant.
Examine the radiator and header-tank hoses for splits or signs of perishing. Replace, along with the clips.
Disconnect the battery. Drain the coolant, saving it if it contains antifreeze. Catch in a clean container and filter through muslin before replacing. Check the strength (See Checking and topping up car antifreeze coolant).
Disconnect the hose(s) from the pump by loosening the clip and gently twisting the hose to and fro to free it.
There may be other parts you need to remove to reach the pump.