When I start the car, the AC kicks in. That's fine. But, it makes a pretty audible THUMP when it does. Sounds like someone bouncing a basketball outside the car (once). Is that normal? Should it be that loud, or making that noise at all?

Also, when I look at the AC compressor, I found some unidentified fluid directly underneath on the frame. I'm not sure if it's coming from the AC, or the engine block (hope not). The fluid seems to be in a linear splash pattern that lines up almost directly with the inner edge of the compressor. That's why I'm suspicious.