That should work well.Or what about a couple of wraps of PTFE tape?
Quick test shows it did leave a nice very thin film on the threads once screwed and unscrewed a bit
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It's what I went for in the end. Too risky I think using fluids that could possibly squeeze out inside the pump with no way of detecting if it has or hasn't. If you can't tell I'm pretty paranoid when working on these things.That should work well.
I used to work in industrial dryers and thermal oxidisers - trying to remove stainless thermocouple fittings was a nightmare if they were assembled without any high temp grease. As soon as it went tight you knew you were in for a bad day…When I worked on stainless industrial centrifuges, we scrubbed the threads with molybdenum bisulphate paste then coated them with a mix of molybisulphate and grease. You know it's galling when it starts to tighten so you try undoing it to start again and it tightens up even more. Horrible.