Most cars have one primary water pump. However, some cars may have an auxiliary water pump in addition to the main one.
Primary Water Pump
The primary water pump is responsible for circulating coolant throughout the engine to regulate its temperature. It's typically driven by the engine itself via the serpentine belt or timing belt. This means the pump's operation is directly tied to the engine's speed.
Auxiliary Water Pump
Some vehicles, especially those with complex cooling systems or features like auxiliary heaters, may have an auxiliary water pump. This pump is usually electrically powered and can operate independently of the engine's speed.
Reasons for having an auxiliary water pump:
- Improved Heater Performance: Like the 1985 M-B 300D referenced, an auxiliary pump can boost coolant flow to the heater core, improving heater performance, especially at idle or low engine speeds.
- Turbocharger Cooling: Some turbocharged engines use an auxiliary pump to continue circulating coolant through the turbocharger after the engine is shut off, preventing heat soak and potential damage.
- After-Run Cooling: To improve engine lifespan some cars use an auxiliary pump to continue cooling the engine after it has been switched off
- Complex Cooling Systems: Vehicles with intricate cooling layouts might employ an auxiliary pump to ensure adequate coolant circulation to all areas.
In summary, while the vast majority of cars have only one water pump, some vehicles incorporate an auxiliary water pump to enhance cooling performance in specific situations.
