A question that I am not sure how to even ask...

You can also go to Autozone or Advance Auto and rent a radiator/cooling system tester. Basically, you put down a deposit equal to new cost of equipt, use it, and they return your full deposit apon return.
It has a hand pump, hose and adaptors for radiator top and cap. Hand pump has a vage on it- yellow/green/red. Pump it up to see if it holds pressure to about same psi as your cap. If you have problems, it'll bleed off fast. Look for coolant leak, while under pressure. Best to do while you still have V. Cover off.