Renix pressure bottle volume

During proper operation and at operating temperature, how much fluid should be in the pressure bottle?

It should be a little above the center molding line. Don't fill it or it will POP!

I thought so. The bottle was empty this morning so I filled it up to the middle mold line and now the level is about an inch below the cap.

Also, I was able to slowly remove te cap without the coolant boiling out - I thought that you had to wait for it to cool down.

there is that little spout on the inside that sticks up from the bottom. sort of looks like the end of a slurpee straw spoon. fill the coolant to the middle of the 'spoon' looking part of that little spout. its a little less than half the total capacity of the bottle.