[s-cars] Not exactly S-car-related, but very Audi...

[Eric Phillips]

Patient:  1991 90q20V Sedan, hereafter called "Lago".

Problem:  Coolant heats slowly in comparison to S-car and wife's 2.8L
V6 Audi motor, but does finally get to temp.  BUT, gauge reading is
dependent upon driving conditions - on the highway, the gauge barely
comes over the thin mark before the fat mark that is generally
considered "operating temperature" by any Audi owner.  Sometimes it
hangs out below that thin mark.  In town, the gauge hangs out between
that thin mark and the fat (normal temp) mark.

My first thought was a stuck open t-stat.  Replaced it with a good
(tested in a pan of water on the stove) 87-degree t-stat, and guess
what?

Same behavior.  Lago is sick, and I don't know the cure.

I surely have done SOMETHING wrong.  But what?  I seek the wisdom of
other 5-cyl, 20V DIY greasemonkeys...

Eric