Cooling
Water Pump
The water pump circulates coolant through the engine, radiator and heater core.
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Cooling system flow
Interactive — tap a partTap a part to see how it fits in the system.
What it does
- Pumps coolant around the cooling circuit
- Driven by the timing belt, chain or auxiliary belt
- Often houses the thermostat in modern engines
When it fails
- Coolant weeping from the pump
- Rumbling or grinding noise behind the timing cover
- Overheating
- Coolant on the belt side of the engine
How to diagnose
- Look for dried coolant traces around the pump
- Check the pulley bearing for play or noise
- Pressure-test the system
Maintenance
- Replace the water pump with the timing belt service
- Use the correct coolant to protect the seals
Use the diagnosis order. When a part fails, confirm each hypothesis with measurements before replacing anything — codes and symptoms overlap.
Related part
Timing Belt / Chain
The timing belt or chain keeps the crankshaft and camshaft synchronized for correct valve timing.