My 79 240 D usually runs just above 80*, sometimes, at idle in traffic with AC on in San Antonio during the summer, it will climb to just under 100*

Recently had a water pump fail on the 1980 240D - it had been running hot for a while, and overheated on my wife (got over 120*), so I finally replaced it and the t-stat.

I did not test the t-stat in boiling water (supposed to be an 80* trigger) before installing, but the '80 240D still runs hotter, Just took a road trip to DFW, and it ran at 100* on average. But, the temp would sometimes climb to about 110-115* before the t-stat would open and the temp would drop back down to a bit below 100.

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT