I have a 2006 Chevy Cobalt and since I bought the thing, the front suspension makes this horrible clunking noise every time I go over a bump. I don't know how to describe the noise other than it only happens when I drive over a bump (such as a speed bump) and it sounds like the whole front of the car is about to bust apart.
I've analyzed it and it appears to only happen when the strut engage at all (going over a speed bump, driving off a curb, etc). The sound is coming from someone near the top of the suspension so, it's unlikely it is a roll bar or something of that nature. I have a feeling that perhaps the strut mount have failed and that is what's making all of the noise. It doesn't affect how the car drives at all, it just sounds horrific.