Hi Rich,
Loctite 542 is a dark red, almost brown, liquid. It's big advantage is that it is rated at 300 deg.(F) It's big disadvantage is that it's not cheap, currently around $16.00 for a small bottle.
It's never failed me though. As long as the threads are clean, and you let it set overnight. I was turned on to Loctite 542 by Keith Appleton, who has a youtube channel devoted to fixing/restoring old steam engines.
Paula