I did a search through the archives for posts on whether it's necessary to let a turbo car idle before shutting down. Most people said that it's a good idea to let it idle for 30-60 seconds to prevent oil "caking", etc. Not as necessary with the water cooled turbos as it was for the strictly oil cooled turbos, but still a good idea apparently.

My question: I've noticed that sometimes about 30-60 seconds into the idling period, I'll hear what sounds like a fan kick on in the engine area. This noise usually lasts for about 20 seconds or so, and then shuts off. First of all, what is this noise? Second, is the engagement of the device that creates this noise somehow related to the "cooling down" of the engine/turbo? Bottom line: I'm trying to figure out whether I need to wait to hear this noise before I finally shut off the engine.

Thanks. (97 850 GLT)