2002 JAGUAR XJ8 Engine Problems

LET ME BEGIN BY SAYING OUR CAR IS DRIVEN BY MY GIRLFRIEND WHO LITERALLY DRIVES LIKE A GRANDMA. FIRST THING THAT HAPPENED IS OUR TRANSMISSION WENT OUT AT APPROX 95,000 MILES. WE WERE TOLD THAT THIS IS COMMON FOR OUR CAR SO WE LUMPED IT AND PAID FOR ANOTHER TRANSMISSION. AFTER THIS IT WAS THE REAR MAIN SEAL AND THE UPPER OIL PAN GASKET WHICH WAS LEAKING SO WE HAD THAT REPLACED. EVEN BEFORE THAT WE USED TO GET A "COOLANT LOW" MESSAGE REGARDLESS OF THE AMOUNT OF COOLANT IN THE CAR. TURNS OUT THE COOLANT PROBLEM WAS WAY WORSE THAN THE TRANSMISSION. AT LEAST THE TRANNY WORKED AFTER PAYING FOR IT. THE ENGINE COOLANT PROBLEM HAS BEEN PASSED FROM ONE MECHANIC TO ANOTHER TOTALING 4 DIFFERENT ONES NOW. WE HAVE REPLACED THE ELECTRIC RADIATOR FANS, WATER PUMP AND THERMOSTAT. WE THOUGHT THERE COULD BE NOTHING ELSE WRONG. THEN ON...