My Cl-S goes clunk when I hit the brakes. It sounds like it is in the left lower front. I can not find anything loose. What could it be?

 

I JUST started getting this - sounds like something is rolling around under the floor. It happens when i move hard in any direction - braking, sharp turning, hard acceleration.

I think it might be some coins have slipped down behind the tray and are sliding around down there - i've heard of that happening before.

 

I removed like 1/4 lb bolt from rear vents below the searts ... it was driving me crazy till I remove it.

Nashua.

 

You might try tightening the lug nuts. I had a similar sound upon braking or acceleration that was cured by this simple fix.