I fixed this problem weeks ago. Forgot to post the results. Sorry about that.

The problem turned out to be a missing thermostat. Some one had "gutted" the thermostat and put just the ring piece back in the housing.

Anyway, I replaced the thermostat with a new Behr thermostat, a new fan clutch and put the old coolant back in there. It works like a champ now. It hovers right at 85 all the time now. And it warms up quickly (unlike before).

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AJ

1985 300D (SOLD)