I just bought another mustang cobra 1996 and guy told me he just installed new brakes all way around. when the car is in motion the brakes rattle like crazy they stop when i apply the brake's I can even move the brakes up around in calipers a little? what did he forget to put on them? I noticed a brake rebuild kit in trunk new in the box that hasnt been opened. should the brakes be moving around and making noise?