Expert: John Kingery - 3/19/2009

Question
Hello John,

I have a 2002 BMW 330ci convertible and recently started hearing a loud squeal from the engine compartment when Im driving (which gets louder) or in park. I first thought it was the serp. belt, but when I sprayed some WD40 directly on it, the noise did not go away at all. So that told me it wasnt the belt.
The noise does come on intermittenly, so I suspect it may be a bad bearing in the electric cooling fan thats causing the noise, maybe the fan shroud in particular. But I'm not sure, can it be something else like a water pump or idler pulley??
Any advise or thoughts is appreciated and thanks for taking the time out of your day to help.

-Fred

Answer
I'd agree it's not your belt.  Could be anything from idler bearing to waterpump to ps pump to alternator to cooling fan.

If it makes the noise when the car is idling, check under the hood to determine about where it is coming from.  Spraying a lubricant onto an idler bearing will often quiet it...just to see if that is it.

(you're welcome)