There's a noise from under the hood after I shut the engine off! What is it?
 

The really loud noise is the electric radiator fan, which will run for a brief time after shutting the car off when the engine is hot. On the S models with the N14 or N18 engines, the much quieter humming noise you may hear after the the radiator fan stops is the auxiliary water pump that circulates coolant through the turbo. It will shut off automatically after a few minutes. Perfectly normal.

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