In both cases here for each person, I would perform a pressure test on the radiator cap. Your cooling system appears to be functioning fine in as it can dispirse heat. But the problem would appear to be a loss of coolant. When I first got my car, the SS overflow bottle was installed, but the old cap was kept. And for some reason a vinyl hose was connected to the overflow side. I always saw mist inside the hose. And when I alternator belt broke, the car would purge it's coolant almost immediately. Looking at the old cap, I saw that the rubber was hard (unable to seat properly), and part of it was torn. I replaced the cap, no problems since. -Robert vin 6585