I'm with Ilninga on this. Something may be loose in the brake assembly componentry, but the pads are not loose, nor do you need to replace brake fluid. Some anti rattle or hold down clips may be loose. What many of us have found is improperly torqued axle nut. Matter of fact, there is a part number for a kit to replace the existing nut and washer if you pm me I will see if I can find it.