Coolant temperature weirdness

[mallick at mail.utexas.edu]

I thought I had this figured out, but the fix didn't work...

My coolant temp seems to be a little low...it sits below the first "fat" mark on
the temperature guage.  At highway speeds is drops even lower, to the next
lower "slim" mark.  Sitting in traffic it will reach the fat mark and I can
hear the fan cycle on and off.  

It sure looked like the thermostat was stuck open, so I had it replaced with a
brand new 'stat (87C).  The old one looked fine.   The car still behaves the
same way it did with the old 'stat.  I dunno.  Maybe MFTS flakiness??

The only other change is that the water pump is brand new, done with the t-belt
change.  Coolant has been flushed and re-filled, to no effect (not that I
thought it would).

Any ideas?

TIA,

John Mallick
175K and counting....