i think it is the fan and or compresser slowing down
A whistling noise indicates a vacuum leak.
The most common cause of the whistling in a 2003 Impala is a vacuum leak. Any of the lines under the hood could be causing the noise.
wind interaction with the stiff radio arial ?
The head gasket is about to blow.....Typical ford..
Brake booster problem?
Sorry forget to mention it in the motor.
vacuum or air intake hose leaking or disconnected or loose...? good luck:)
Bad fan clutch!!
I would check the serpentine belt and pulleys
its most likely the clown wheels that the wanna be gangsters put on the car
I would think that you have a leak in your exhaust system.
I COULD BE THAT IT IS NOT LINED UP, NEEDS SHIMMS