Remove the four screws holding the top on the mono valve with engine cold, radiator cap off!! Gently lift the insert out of the mono valve (pay attention to how the wave washers and spacers stack on the insert). You will most centainly find a torn rubber diaphram! Replace with a monovalve repair kit from an advertiser on this site. Classic symptom of ruptured mono valve diaphram. Also do "search" for mono valve to locate it and what it looks like. Running 50 to 60 degrees is a symptom of a missing or stuck open thermostat.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.