From what I can tell, air is getting into the cooling loop somehow, and forcing water out of the radiator by over flowing the overflow tank.  When I'd stop to top off the coolant, there'd always be a out-rush of air when I open the rad cap (after cooling down for at least an hour.)  There is nothing unusual in the exhaust, it is clear and mostly odor free, all the fluids look the way they are supposed to.
This upcoming spring, I'll be returning a car I lease for business, and will likely buy an over compensating pickup truck.