I have a 2002 Trailblazer LT, in the year or so, when I first start it up the fan on the engine makes a loud roar. When I drive down the street it sounds like a dump-truck. After about 5 minutes it tends to go away, but on really hot days, it is more frequent. There is also a big loss of power when driving. The higher the rpms, the louder the noise. Dealership said it is just the way it is and it isn't fixable. This isn't the case as it wasn't like this when the car was new. Anybody experience the same thing? Ideas on how to fix it?