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Coolant pump:
The coolant pump (also called water pump) ensures that the coolant is circulated through the engine block. The coolant pump must pump a large amount of coolant through small cooling channels, through the radiator, through the heater core and sometimes also through the water-cooled turbo. The coolant pump is often driven by the timing drive or by the auxiliary belt. The pump in image 1 is driven by the auxiliary belt (the pulley is removed) and the pump in image 2 is driven by the timing drive (see the toothed pulley). On the left side of both coolant pumps, the impellers are shown, which provide the fluid displacement.
In the image below, the coolant pump is shown as number 4. It is driven by the auxiliary belt. This technique is often used when the engine is driven by a timing chain. Some manufacturers choose to also use this with a timing belt. The advantage of this is that if the coolant pump starts to leak or seizes, the timing belt will not be damaged.
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