We've had a 96 Deville since 97. It NEVER ran over 205 on a hot summer day even in heavy traffic. Last year it started running hot and up to 225 in traffic with AC not on but most of the time on the interstate from 203-210. I changed the thermostat and water pump with new GM parts. It still runs the same temp. Yesterday was 26 here and it still ran 206-212 driving 50 MPH on a snow packed road. The coolant level stays full. There is no leaks. the Cadi dealer I talked to thought it could be a radiator problem. When I replaced the water pump, the inside of the coolant system was very clean and the pump came out fine so that makes me think the rest of the coolant system is clean. I've heard people say not to worry about running that hot but if it didn't do that from 96-2003, something is not right with it. Any others ran into this problem?