I've found ambient temperature greatly changes my engine temp readings. If it's 33C or higher outside it seems to hang around 100C. If it's any cooler it will stay around that 85-90 range. I have a brand new behr radiator installed by the dealer. I think I may replace the expansion tank cap. Though I did onetime open the tank when the car was hot (bad mistake) and the car nearly overheated on the highway, had to turn the heat on MAX and it came down pretty quickly. Got home and dumped antifreeze in and it was fine. Then I got the new radiator so I have MB coolant as of now and the level seems to be fine. Right before I got the new radiator there was obviously a leak in my cooling system because it would leave coolant in the driveway, now it doesn't leak a drop of ANYTHING in the driveway. Thoughts?