I FAILED TO LEAVE THE CAR IN 1ST GEAR ON AN APPROXIMATELY 4% GRADE. I ENGAGED THE PARKING BRAKE AND LEFT THE VEHICLE. THE VEHICLE REMAINED PARKED IN PLACE FOR 20-30 MINUTES. SOMEWHERE BETWEEN 0 AND 30 MINUTES LATER, THE PARKING BRAKE RELEASED AND THE VEHICLE ROLLED DOWN THE GRADE, CAUSING DAMAGE TO THE VEHICLE AND NEIGHBOR'S PROPERTY. I AM AN EX-BRAKING ENGINEER AND HAVE REPRODUCED THE DEFECT MULTIPLE TIMES WELL UNDER THE FMVSS 135 PROTOCOL LIMITS OF ACCEPTABLE PERFORMANCE. I COMMUNICATED THIS TO FORD CUSTOMER CARE AND THEY WISH FOR ME TO HAVE BODY DAMAGE REPLACED THROUGH INSURANCE.