Howdy, new guy here. I have a 97 F150 with the small v8, about 222K Kilometers (it's a Canadian truck). Among other issues, it has..."intermittent" heat. IOW, it takes forever to warm up usually, and sometime the gauge sits at the top of the hot mark, but I don;t think it's all that hot really. It'll eventually get to blowing warm, not hot, air. The previous owner told me they thought the heater core was plugged, so I flushed it. Right after that I had good heat for a little while, so I don't think it's really plugged.

What I did notice was that the anti freeze looked awfully heavy, I mean way heavier than it should look. Of course the rad is sealed so I can;t really get a good look. Former owner told it "had that orange crap in it" when he got and he drained it and changed to the green stuff. Is it possible there was enough orange left to cause the green to gel a bit? I understand that more or less what happens when they mix.

I've had vehicles before that needed the antifreeze changed when it got old ahd a lot of junk in it and this acts kind of like that. Would a system drain and flush maybe help or am I looking in the wrong place? I'm familiar with the mixing door issue and the lousy heater core issue.

Thx- you guys have a good site here.