When the engine is cool is the coolant supposed to be up to the level of the radiator cap? My radiator seems to transfer about a cup of coolant into the overflow every time I drive the car but it is never gets sucked back into the radiator when cool.
When the engine is cool again, I remove the radiator cap and fill the radiator up to the top. I even make sure I squeeze the top hose to get the bubbles out. I know it sounds like there is is a bubble in the system, but I have done this at least 10 times.