Q&A

 Rookie

I know my thermostat is 'broken' - it's been running a little cool (gauge at 45%)and is slow to heat for over a year now. My IR gun says temp of upper hose near engine is 165-170. For a $300 simple thermostat replacement bill,I'm OK with that. Gas mileage is great (got 31 on last trip).
However, recently...
When I came to the end of the freeway offramp (and road noise) I heard my radiator fan running. A few miles later when I parked it was still running and would run about 5 sec after starting the engine. The dash gauge was reading just a hair cooler than 'my cooler than normal' normal - say 40%. Hours later, it still ran after starting the engine. At the end of that return trip I opened the hood and felt the lower hose - it was COLD. The upper hose was very warm. Here's the good part - when I squeezed the lower hose - just to see if fluid 'gooshed' up into the reservoir (which it did) the FAN TURNED OFF!
Synopsis...
Tthe SES engine outline light came on after charging down a ramp - it went off a day later. It's been popping on and then off a day or two later a few times now. (I wish I had a code to give you, but I don't.)
Now, massaging the cold lower hose doesn't necessarily turn the fan off.
After filling up after a freeway drive (and the fan still running) I made a sharp swerve into a left-turn and the fan turned off. When I got home I felt the lower hose - it was warm. All this time the dash gauge was at 40%. Oh, when I was on my long freeway drive I turned on the heater to full blast, just to see how hot the air was, and the SES light came on. The air temp ramped up to what seemed a little too hot and then seemed to slowly drop a little - the dash gauge even seemed to drop a hair.
Today? The SES light is off, the fan is not running, the lower hose is quite cool and the upper hose is nicely warm. What the heck is going on?