so I'm after a ride without a thermostat. Outside temp. + 26°C
Everything seems fine. Both hoses of the radiator have a similar temperature. The car was warming up a few minutes longer. The temp. gauge shows "R" (sometimes between "O" and "R" when I stopped at traffic lights). The fans only turned on when entering the garage. After stopping, there was no boiling, no bubbles. After a while, I could open the header tank cap and everything was ok. I looked again at the thermostat and it has scratches in one place. Maybe it just blocked itself sometimes.

Last question I have:
What is the approximate difference in the temp. gauge display in terms of degrees Celsius between the letters N - O - R and M? Does anyone know?