I have a loud fan sound as well. Crazy loud in direct relationship to the speed of the fan - very annoying. I finally figured I'd look into it and see what was going on and I found there was a radiator tube that was bolted to the frame. However, the bolt coming out of the frame had broken - so it was just vibrating against the frame of the car. I managed to get a nut to hold onto the little bit of thread that was left of the bolt and then added another bolt and nut to the nut and managed to pinch down that tube again between the 2 nuts. It reduced the noise significantly - but I know it will eventually work itself loose again.