Well, that is where you need to get the air out from. But my memory says some of those bow ties needed help in purging air from the intake...
(fwiw.. my memory ain't what it used to be!)

You might try loosening a fitting ( like the temp sensor) and seeing if air or fluid leaks out. I've never played with a 2 radiator system but air will be at the top and you need to find it and release it. HTH..