Fan Clutch.
I just wanted to add to all the comments about the fan clutch going out. Mine just did, but a little f.y.i. to save everyone $ I bought the fan clutch at auto zone for 200.00 dollars, and the labor from a local mechanic was only 100.00 dollars. Do not go to a dealer for this problem; they will charge you a lot of money. Chevrolet refuses to recall this item, which causes all these complaints. I think they should. I knew it was the fan clutch due to this web site; thank you everyone for your info. My problem was just like everyone else's. At first my engine sounded like a "jet engine" on and off. Then it was constant for about two days and my service engine soon light came on. The mechanic plugged it in to the computer system and it read out the code that indicates fan clutch high. Now my car is running fine and no more SES light.
This website does provide some very helpful info. You were very smart to buy the fan clutch and have someone install it rather than the dealer. Dealer charges are outrageous.
I'm a mechanic and I always urge people to buy a good repair manual on their particular car (such as Chilton's) and do your own repairs. Most repairs, such as your fan clutch and such things as brake pads are so simple you can do it yourself and save a lot. Most disc brake pads are so simple to replace that my wife can run out and replace them in half an hour.
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