So after my huge b3 friction disc and seal tranny over haul (tranny now works awsome!), my yellow coolant light came on. Since it had been about 3 years since my last coolant change I when ahead an flushed the system with water and refilled using 50/50 (eye balled) MB coolant and distilled water. The last 5 days my car has been blowing out luke warm air at idle or low speeds and hot at highway speeds. The engine temp now stay at or under 80c after running 20min....which is 5-10c less than before (ranged 80c to 90c). I've been searching for this issue with little success..I've read t-stat, monovalve, to heater core issues? I tried burping the sytem by squeezing the upper hose and running it with the coolant over flow cap off. I've also ready the w124 self purges the air out of the coolant system. Great toasty heat at highway speed with the engine temp at 78-80c..but a stops it's luke warms and engine temps at 80-85c) I think it's gotten a little better slowly but ...what gives? Could have my eyeballed 50/50 been wrong...too much water or too much coolant? Any ideas? Thanks!