PROCEEDED TO BACK OUT OF PARKING SPACE. BRAKES BEGAN MAKING LOUD GRINDING NOISE. PULLED BACK INTO PARKING SPACE WHEN BRAKES FAILED. BRAKE FAILURE LIGHT AND CHIME WAS ACTIVATED. VEHICLE WOULD NOT STOP AND HIT THE CONCRETE HANDICAP SIGN STOPPING THE CAR. PREVIOUSLY HAD PROBLEM WITH NAVIGATION UNIT WHICH WAS REPLACED ONCE AND READY FOR SECOND REPLACEMENT. TOLD SERVICE MANAGER WE THOUGHT IT MAY BE ELECTRICAL RELATED, NOT DEFECTIVE UNITS. BELIEVE THE PROBLEM WITH NAVIGATION UNIT IS RELATED TO THE BRAKE FAILURE. AFTER ACCIDENT, HYUNDAI HAD AUTOMOTIVE ENGINEERING CONSULTANTS EXAMINE CAR. HYUNDAI SAID THERE WAS NOTHING WRONG. HOWEVER, SERVICE MANAGER AT DEALER SAID THE CAR HAD MAIN HYDRAULIC FAILURE AND NEW PART WAS ORDERED. IF NOTHING WAS WRONG, WHY WAS HYDRAULIC UNIT REPLACED. HYUNDAI REFUSED TO DO ANYTHING. *TR