Ok i had a relevation... or yeah. The filler neck seems to never be full after filling and driving it. But it is under negative pressure with the car fully cooled, after driving... AST isn't for pulling the coolant from the AST to the filler neck.. It pushes the coolant through the lower hose. Ahhhh. when running. When it is off it sucks the coolant from the overflow tank and still pushes down through the lower hose. So in actuality the AST is never full. unless it is pushing coolant to the overflow. Only when the coolant is boiling. so if you are losing lots of coolant through the weep/bleed hole in the overflow then you might have a slowly failing water pump. cause it isn't pushing the coolant through the engine completely. thus pressure is upped quite a bit and coolant flows freely into the overflow. Then the temp guage goes up and buzzer sounds but eventually will go back to normal due to negative pressure sucking some of the coolant back into the system. But cause of the slowly failing pump it doesn't take back in enough coolant. Am i right or am I right? right right right right right?