Poil
Just so that we don't send someone on a wild goose chase. I would just like to clarify the product you are speaking of.
242 Loctite that you have mentioned is standard blue medium strength threadlocker we all know and love.
http://www.loctiteproducts.com/p/t_l...r-Blue-242.htm
Can you double check your bottle of red HVAC sealant