We bought this home that has water baseboard heat. We installed a new zone to heat our basement. Replaced the automatic bleeder, expansion tank and automatic fill. Used a transfer pump to push air out of all 3 zones. It makes it anywhere between 2-4 days and then the water noises in the basement zone start again. It seems to be when more than one zone is running. We have shut of the automatic fill to ensure the pressure stays where we set it and so far so good. There is no signs of leaking any where. We don't know what to do next. We used pex pipes on the basement zone that was added. Please help.