[Healeys] coolant temp sensor

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List: I just installed a new oil pressure/temp gauge in the healey rebuild.
Even though I have the backing nut firmly tight the sensor itself is still
slightly loose, obviously, the best way to tell if it will leak is to fill the
radiator but I am too much a coward to do it, I need someone to tell me that
it is perfectly normal for the sensor to be loose or am I missing something???
Many thanks.

Brad Holden
67 BJ8 soon to be running (I hope)