1997 Mercury Marquis possible brake pad rattle?

Horrible rattle when going over bumps in the road. Sounds as if the pads are loose. Replaced the front pads and rotors w/ rattle clips. This worked for about a week, it came back. Someone suggested possible bad caliper piston. Bought loaded calipers and replaced. Didn't change a thing. Rattle is not present when brakes are in use, which is why I thought it was loose pads. Could this be a possible front end problem? Also don't know if this is a related problem, but when coming to a stop the brakes seem to pulsate the slower the car travels. Thought maybe bad rotor, but it only seems pulsate at low speeds? Any help would be great. This rattle is bugging the hell out of me.