I would think vclutch either works or doesn't ... I suspose bimetallic component could get stuck and then release ...

More likely tstat gets stuck ... I am beginning to think there is a failure mode associated with tstats that, after being in the engine for a long time, then fluid drained, they stick ... long shot, but this failure mode seems to happen a lot ...

If you think magic is at work, replace the cheapest and easiest part first!

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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