Mine hovers just below the 100C degree mark no matter what the temp. It can be below freezing or approaching 100F as it has been the past few days and it still stays rock solid at around 97C. The only time I've ever seen it break 100C is when i was installing my veg conversion and didn't fill it up quite enough. There was still coolant visible in the expansion tank but just barely. Even then it only broke the mark while driving 75 down the highway for about 15 minutes, and even then it was only about a needle's width over. Adding the proper amount of coolant fixed it. My brother has an 84 300D that a p/o modified so that the aux fan would run all the time. If I remember correctly his runs about 90C. Both cars appear to do fine at these temps.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo