Did this procedure when I searched online for the problem.
BUT I have bigger problema now
I drove off with a normally filled expansion tank. When I returned, the tank was completely full and coolant was coming out of the valve at the top.
As a test, I removed the oil filler cap and found that there was a vacuum. I'm not sure what's normal, but it seemed very strong to me.
According to my research, it could be the AOS?
The drive itself went smoothly. Car idles fine, water temperature is as it should be and oil pressure sits at 1bar at idle.