You are correct, I put a tee in the heater supply hose off of the cylinder head by the oil filter. It travels to a plate heat exchanger then back to the tank in the trunk. The return line exits the tank and joins the line between the aux pump and the water pump. My question is whether that is the right location for the return line. I read on another post that it was placed after the aux pump. I will loosen the line and try to remove any air bubbles.