94 Voyager ~ Intermittant Heat

Beginning problem was no heat. Mechanic discovered coolent was low because of leaking water pump. Replaced water pump and thermostat. Heat worked for two days. Mechanic discovered coolent was low again but no external leakage and blowing steam out exhaust. Problem probably bad head gasket. I replaced the head gaskets myself repairing the problem with the dissappearing coolent but heat is still intermittant (mostly non-existant). I flushed the heater core in both directions with no blockage apparent. Heat still non-existant. I noticed there is no change in pressure/vacuum at the vacuum line going to the heater core heater valve. I pulled the heater/ac control assembly from dash looking for the other end of the vacuum line that supplies the heater valve but could not find it. Any suggestions?