Check wheel lugnuts torquing, wheel bearings, brake pads and brake calipers for a start.
May, 29, 2012 AT 6:29 PM
Most common cause of a single knock each time you press the pedal is rear shoes out of adjustment. The front shoe catches the rotating drum and turns with it forcing the rear shoe into the drum. When they're out of adjustment the rear shoe bangs into the large anchor pin on top. Ford has always been famous for parking brake cables rusting tight and that can hold the shoes out enough so they no longer self-adjust. Readjusting the shoes manually will stop that noise for a long time.
You might also check at auto parts stores that rent or borrow tools to see if they have a "Chassis Ear". That's a set of six microphones, a switch box, and head phones. You clip the microphones to suspect points, then listen on a test drive while switching between them. Be aware many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find elusive noises.