i own a 1999 cadillac sts haviving over heating problems has been to the shop for a hole year and noone can seem to fix this over heating problem. when i bought this car the heat would go on and off and not blow heat then all of a sudden it went all the way out the heat so i take it in to have serviced and the guy said they changed the water pump and themestate well it still over heated so i took it to a few more places to have it serviced and now it is over heating right off the bat help please.