WHENEVER AT A STOP IN TRAFFIC, THE BRAKE PEDAL DRIFTED TO THE FLOOR CAUSING LOSS OF BREAKS RESULTING IN STRIKING THE CAR IN FRONT OF ME. THE TRUCKS BEEN AT FORD TO REPLACE MULTIPLE PIECES OF THE BRAKE SYSTEM WITH ABSOLUTELY NO BETTER RESULT. THE MASTER CYLINDER RESOVIOR WAS FOUND EMPTY TWICE PRIOR TO THIS PROBLEM SURFACING.