You may also be overfilling the radiator coolant should just cover the core or about 1 inch below the cap seal on a non overflow system. This is to allow for the coolant to expand and not be pushed out the vent tube.
Beat me to it. The fill level needs to be down about an inch. Or as I do, let it bleed off the excessive amount. It will stop the bleeding off of the fluid. My 69 Dart does the same.
