Eric - Yes, that collar under the radiator cap can come loose and completely detach from the tank below it. Mine did. I remember I replaced the radiator cap but it was really hard to remove. As I twisted on it with all my strength, instead of the radiator cap turning off the collar, I turned the collar off the tank. It must have been loose because I don't think a human has the hand and arm strength to break the solder joint. Although I do remember a man where I grew up who had a small tool box full of one-handled pliers, etc., that he had broken off one of the handles. Anyways, when that collar detached, we used JB Weld to re-attach it. That was five or so years ago.