Originally Posted by shivers
... here's how to "bleed" it. After the car has sat overnight, take off the radiator cap and start the car. Turn the heat and fan on high. Let car run until the radiator fan has come on twice. If there's any air in the system, it will work it's way out and come to the top of the radiator.
Or you could just open the union bolt until a steady stream comes out with no bubbles, and close it.
