Water Pump

Most pumps are driven by the auxiliary belt or the timing belt; some modern pumps are electric or switchable so they can stop when the engine is cold. The bearing and seal wear over time. A small weep hole lets coolant out when the seal fails, as an early warning.

Most water pumps are driven by the timing belt or auxiliary belt; some newer engines use electric pumps. Water pumps wear gradually. The seal around the shaft starts to seep, the bearing becomes noisy, or the plastic impeller on some designs cracks or slips on its shaft. An electric water pump can also keep coolant circulating after the engine is switched off, cooling the turbocharger and helping the heater in start-stop traffic.

An impeller inside the pump pushes coolant through the engine passages and on to the radiator and heater core. An impeller spins inside the pump housing and pushes coolant through the engine block and cylinder head.

A failing pump causes leaks, a whining or grinding noise and overheating. Where it is driven by the timing belt, it is usually replaced together with the belt. Leaks from the weep hole, a whining noise or overheating can mean the pump is failing. When it is driven by the timing belt, it is often replaced at the same time as the belt.