I started my car up yesterday, it wasnt really cold, i had just run into a store for about a half hour and came back out again. I started it and i heard a whirring noise inside my car coming from under the hood. every time i revved the engine it went away, but when i let it idle it was constant. I opened the hood and heard it coming from what sounds like the engine. I started driving and it went away completely. Does anyone have any ideas what this could have been...i havent heard anything like that before. Thanks in advance...John.