I finally replaced the heater valve and couple other associated items. Im in S. Fl! Couple years ago , its hard to believe time went by so fast , I had a waterfall sound behind the dashboard. After testing the old heater valve I realized that it must have been the culprit as it was stuck partially open. In any event I took the opportunity to replace the lower radiator hose ( The upper was done a year or so ago ) the rubber inlet and outlet hose to the heater core.
I used Zerex G05 antifreeze which I sourced from the local Napa store .The system was flushed , 13mm wrench for the drain located on the block ...see Faqs I replaced the thermostat rubber "O' ring at the same time. For the heater valve I used a new Motorcraft Yg 136 . It is best to remove the flame trap and associated hose to gain access to the heater hose on the block next to the oil condensing unit . Space is quite tight and at one point I was tempted to remove the inlet manifold. Took me about an hour and a half.