Hi JimY,
We are in Memphis and our temps outside aren't quite as hot as yours but close enough. This car ran great for two years b/f has had it; within the last year developed small crack in rad that JBWeld held tight until about 2 months ago when I replaced rad. We have only had this problem since replacing radiator. I've contacted Wiley Imports (an exclusive MB parts/service/salvage shop) here in Memphis. He has the Behr thermo and correct rad/tank cap for about $35 for both. I'm going by to get them Monday. It's holds @ about 82-85C on the highway and spikes to about 95 when exiting, but at slower speeds, 40mph and under, is when it really starts heating up/overheating. I'm not giving up on this problem. I'll keep trying til I get it right.
Thanks for lurking.
DebN