[ngoma]

I'm thinking there should be a common paper gasket between the radiator hose flange and the cylinder head. Might be a good candidate for a form-a-gasket product like Permatex Great Stuff or similar?

Not familiar with Pirma Tex but if it is recommended for coolant flange or water pump etc. it would probably work fine.

Now remembering mine had a stubborn leak there. Really took a lot of scraping and scrubbing to get the mating surfaces uniformly flat as possible, then I used a Permatex product for forming a gasket for radiator hose/thermostat flange/water pump.