Originally Posted by tqwrench

I have that bleed passage in my '83 240D. I'm going through all the same gyrations you are. Flushed like madness, latest was Thermocure for a week in there. Parts cannon loaded and shot. At least 5 different thermostats, the water pot tests, so on and so forth. I'm leaning towards the dash gauge at this point (on mine). I caught it dropping to 80°C and parking there for a few seconds once, and then it "ticked" right back up to about 95°C. Stories of bad solder joints and bad grounds on the cluster side of things. Might be worth investigating.