Guv Bob wrote:

OK, back to the beast again. On the road, temperature is just slightly
above mid-range, where it has always been. When stopped with engine
idling, the temp slowly increases. If I set for more than a few minutes,
it approaches max full scale. When I drive off, it comes back to normal.

Another symptom - that may or may not be normal or related - is when I
start up cold, it takes a good 10 minutes to come up to temperature.
Other car takes about 2 minutes.

R/R fan clutch -- no change.
Are you sure the fan clutch is good? If you rev the engine to 3000 RPM
or so, the fan should really roar, especially when the engine is hot.
Since the problem occurs at idle, maybe you can spray a spot of paint
on one fan blade, so you can gauge the fan RPM. The fan clutches are
supposed to couple well at low RPM, and when hot, and less well when
cool and at higher RPM. I'm assuming a fluid clutch.

Jon