I am in need of some help. I have an exhaust leak but you can only hear it when under a load like climbing a hill or passing. the manifold studs and clloector bolts are not loose no visible crack on the manifold either. Any ideas?

 

I just had this problem on my 01 expy 5.4 and it turned out to be the passenger side rear exhaust manifold gasket. Yes there are two on each side or at least you buy them that way from ford if you want the metal ones. I just pulled the old manifold off to check the gasket and it was blown out all the way to the rear. I bought a new one at the dealership and put it in (about 2 hours labor). Now it is gone and now the vehicle is really quiet. I never noticed it before except like when you said, but after I fixed it, Big Difference!

Later,
Devildog101

 

i dont want to start another seafoam debate but... just use a little, just a 1/4 of a can if that. that stuff can find the smallest exhaust leak.look for the smoke.