I presume you meant: “to the right side of the radiator”? I understand that this even smaller pipe from the manifold to the radiator is meant for the coolant bypass circuit if the (correct Smiths #85025) thermostat is closed.
So, yes, I was referring to the smaller pipe from the right side of header tank to the right side of the radiator. Since there is no real connection from the header tank to the pipe that runs directly through it from manifold to radiator left side, the smaller pipe I was referring to is indeed the only pipe that can allow the cooling system to be filled - thus its MAIN purpose. I HAVE read about people blocking this pipe!!! 