If it ran cool without a thermostat, but hot with a thermostat, why would a new fan make a difference? Thermostat sets the minimum temp, right? Without tstat no minimum temp, so runs cool ... add a tstat and runs hot ... but with new fan runs at tight temp?

After having a spate of bad thermostats in the early 1980s on a 2002 BMW, I learned from several of the BMW club that they consistently drilled small holes around the perimeter of the tstats disk (internally, of course :-)). I think the logic was that you allow some flow of warming water which helps the tstat open ... have done this consistently since then on most tstats - I suppose it will, as a side effect, slow the warm up cycle, initially?

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg