The thermostat is opening. I'm sure of this because when I topped the radiator off, I left the radiator cap off to watch the coolant level as I reved the engine. The coolant immediately sucked down about an inch and rose back up immediately when I let of the throttle. The heater is also working so I'm getting flow throught the core. There seems to be great circulation. The reason for my overheating was the loss of nearly a gallon of coolant at which point, the heater went cold and the engine temp began rising. So I guess I should clarify my original question. I'm losing coolant from some where fast but I can't locate the leak. I read in my haynes manual that coolant leaking from the "weep hole" on the bottom of the water pump means the seal is blown. What's got me confused is, I was trying to find the leak and I saw bubbles being blown from a hole above the shaft on the water pump (not below). I'm not sure that coolant was coming from this hole or if it was simply blowing bubbles in the coolant that had leaked onto it. Does anyone know if there is supposed to be airflow through the "vent hole" or is it a sure sign of the pump needing replaced?