The 50 is 50C, which is where it has been since I got the car, 5 years ago. I drove it about 10 total miles without the thermostat to get a new one, which I installed when things had cooled down. Disregard the bubble test, I didn't do it right.

It drives fine and sounds good, I drove about 30 miles with the new thermostat.

Now I am thinking I should check out temperature sensors for the engine.