On Thursday, 29 October 2020 at 14:37:23 UTC, Roger Hayter wrote:
I have a brass temperature sensor about 14mm in diameter, no 'O' ring or
shoulder, just seals on the threads into an aluminium cylinder head. What
should I use to seal it? Nothing, ptfe tape, ordinary blue loctite, plumbing
thread sealing compound (a bit too permanent I would think) or something else?
Glad of any advice.

--
Roger Hayter

Does it actually NEED sealing - ie is it going to leak coolant or does it screw into a blind pocket? I'd simply put a smear of anti sieze or a corrosion inhibiting heat sink compound on the thread if there's no leakage likely