After I arrive somewhere, turn the car off, remove the key fob and exit, I hear a fast buzzing sound last for maybe two seconds more coming from under the hood. Something is running on, something spinning fast and slowing quickly to nothing - could it be the turbo? Any ideas? It's a 2010 with about 85k on it, and I still have my Carmax warranty on it, FYI.

 

There is an auxiliary electric water pump that runs after the car is shut off. The radiator fan also runs after the car is turned off. The water pump is pretty quiet, so it's most likely the fan that you are hearing.

 

Thanks for the reply. It's definitely not the radiator cooling fan, I know that sound well and it too runs - but for quite a few minutes longer. This is a fast, smaller, more metallic buzzing/grating sound, it sounds like a bearing is going in some smaller rotating part. The sound dies out very quickly (just a few seconds after engine off) and is not responding to a thermostat - it's simply running down.

 

The only other thing I could think of would be the electric water pump? The one on my car is fairly quiet and definitely doesn't sound like a grating worn bearing. I suppose it's possible yours has gone bad?

 

Aux water pump: 11537630368

It will make a buzzing noise after you shut that car off.

https://www.northamericanmotoring.co...ound-like.html

 

Took it into the (Universal City, CA) dealer and the guy (who's really knowledgable actually) tells me it's not serious, but is a known problem. He says it's the solenoid that maintains the vacuum - it's reciprocating and that's the buzz. Says it's not a safety problem, actually recommended I don't bother doing anything about it.

 

Yea, the buzz noise is the water pump doing its thing after shut down.