ENGINE SHUT DOWN WHILE DRIVING UP MOUNTAIN ROAD DUE TO OVERHEATING. PROBLEM DIAGNOSED BY DEALER AS BLOWN HEAD GASKETS DUE TO LOOSENING OF HEAD BOLTS. PROBLEM IS USE OF STEEL BOLTS DIRECTLY IN ALUMINUM BLOCK WHICH VIBRATE LOOSE OVER TIME, CAUSING LOSS OF ENGINE COOLANT. WIDELY RECOGNIZED PROBLEM BY REPAIR SHOPS AND THERE IS A TECHNICAL SEVICE BULLETIN ADDRESSING THIS REPAIR; NEVERTHELESS CADILLAC CLAIMS IT IS NOT AWARE OF ANY DESIGN DEFECT AND REFUSES TO ASSIST WITH REPAIR. REPAIR COST $4,600 TO REBUILD ENGINE OR $7,800 TO REPLACE ENGINE. PROBLEM DEVELOPED WITH NO WARNING AND CAUSED OCCUPANT AND FAMILY TO BE STRANDED.*AK