The reading of the Temp I sender should go up a little when you are going
down the road.  It will also go up with a colder ambient temp.
I would suspect your warm up air valve (located on the passenger side head).
There is a way to test this cold with a flashlight and a mirror (to see if it
is opening or not) that might be in your Bentley (I forget if I saw this in
the Bentley or my Jetta's Haynes manual).  It could be that you are having
vacuum leaks down at the warm up air valve or that the valve itself is no
longer working.  I would inspect all the vaccuum lines down there for cracks
and then do the test on the valve itself.
Let me know what you find.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
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