BRAKES PADS WERE REPLACED AND THE ROTORS WERE TURNED. BRAKES OPERATED NORMALLY FOR APPROXIMATELY 4 MONTHS, THEN INTERMITTENT GRINDING NOISES WERE HEARD. VEHICLE WAS TAKEN IN FOR REPAIR OF NOISE PROBLEM AND MECHANICS SAID EVERYTHING WAS WORKING PROPERLY AND THE NOISE WAS NORMAL. THE BRAKES THEN FAILED WHEN ATTEMPTING TO MAKE AN ABRUPT STOP AND A MAJOR CRASH OCCURED.