Tried to bleed the system with this method:
https://rennlist.com/forums/996-forum/513364-engine-coolant-bleeding.html
I got to point 9 or 10, the car turned on the fans, thermostat was most probably open and the coolant level kinda stable. All of a sudden coolant gushed out of the open cap, at least half a liter. I turned off the engine to clean up, and shortly after starting it again, the same thing happened again. It didn't seem like air was coming out, the coolant was just pushed out of the expansion tank? With the engine off, the coolant level sank about the same amount as coolant was spilled