Well, my issue is resolved. Yay. I got one of those Prestone radiator flush/cleaners and ran that. Then flushed it using one of those flush kits where you connect your garden hose to the heater inlet hose to backflush the system. Then I refilled it.

It seems like the PO must've tried to put in some of that brown stop-leak at some point, and I was a little worried that it might leak again once I flushed it, so also added some K-Seal. I'm usually very leery of stop leak stuff, but that stuff gets great reviews and I it worked well when I couldn't find a coolant leak in my car.

Started it up and let it idle for a few minutes, and it got up to normal temperature as one would expect.

 

You might want to replace your thermostat cover.

They are made out of pot metal, and the coolant can flow around the edge of the thermostat once it is installed when the cover is worn out.

Also, stick with the 195 range thermostat. You engine will run better. The 'summer-stats' that used to be around were not ment to be used in our modern trucks.

 

I just replaced my radiator and had a year old 13 lb stant 10329, saw a racing cap STANT 18329 and when it cam said 14 lb, is that going to hurt anything using a 1 lb difference when the old one seems to be not holding pressure well
Thanks
93 f150 5.0 XLT 4EOD 4x4