I'm putting in a new "L" shaped coolant bypass metal tube hose on my E150 back of manifold, it's a pressed fitting into the top manifold, but, I want to use either high temp RTV, stays rubbery soft or JBWeld to seal it up good, since I dinged up the hole on the manifold a bit getting the old one out. I believe the RTV temp is 5-600 degrees, where JBWeld is about 2-300 degrees, does it really make any differnce? I know the JBWeld, believe you'd have less work time since it hardens faster..etc

 

I agree to use JB or epoxy or something similar that gets hard. TAke a rough piece of sand paper and scratch up the surface an inch in diameter so it has something to stick to.