There was a post quite a while ago where loud squeaking turned out to be a dry rod bearing. However, the motor wouldn't stay together too long if this was the case. I had my damper start squeaking at one point. It wasn't really loud and only did it at idle. I use clear plastic 1/2" hose to listen to my motor. I put one end to my ear and get as close to the object as possible with the other end. I find that is a very directional listening tool.
