I have noticed now that its getting warmer that when I have the air conditioning on and the compressor engages, I feel a violent clunk through the car, almost like something hit the car. Everything works fine and I was wondering if this is an issue or just how it is?

 

They are noisy and I can occasionally feel mine engage, but I wouldn't say it is violent by any means. It may be a problem, hard to tell unless you can compare it to another 2008 Mustang.