Cleaned out the 8RT with white vinegar, and neutralized with baking soda as recommended here on the Fordbarn. Thanks Fordbarners, it worked great. You should have seen the crud that came out of the block & heads. (Radiator is new, so I didn't need to do that part.) Here is example of before and after vinegar on the two thermostats. Left is done, right, not yet.
Last edited: