I was experiencing the identical symptoms you were. Changing the radiator to an aluminum radiator made all the difference. I think my old one was clogged or something. I did have it cleaned out by a professional (supposedly), but the old copper one would never make the car run cool. $200 later the car NEVER gets above 190F. Best money I've spent on the car so far. Not saying the radiator is the only potential problem, but it worked for me! I don't even have any of the fillers talked about previously. The only reason I didn't change it out sooner was from lack of research. I was expecting to spend $1200 or so on one of the "Be-Cool" radiators...check eBay...found mine for $200