[foyburgher]

Thermoswitch is ok and I replaced it 6 months ago.

I think my 2 clues are:
a) The overheating problem happened suddenly, after no overheating problems for 1 year, and driving about 50 miles with temps in the middle of the gauge right before it happened.
b) the upper rad. hose is hot, but the radiator is cold. It doesn't even heat up enough to kick on the fans. But the engine starts to overheat...