Can you explain the function that the gate serves? As I see it, it is either open or closed. Since the heat has been gradually getting cooler over the past few weeks, I would imagine that if it is the gate, it is only partially opening and closing. Is this a correct assumption? How do I check and fix it?

Also, are you saying I'm smelling something else other than coolant? I definitely smell the sweet smell of antifreeze. I checked the level and the radiator is full. The other tank is about an inch low... pretty normal.

Yea, the Jeep is well taken care of, but I've lived in NC (beach, salt, etc), CA (scorching heat), and now upstate NY (or should I say the North Pole), so the different climates have been hard on it.