Sorry if this topic has been discussed to death here. I have a 99 F-150 with a 4.6. Previous owner had engine replaced. Runs great except for leak at the flanges where the collector pipe connects to the manifold. Have checked all the manifold bolts. One shop took the pipe down and re-belled the mouth of the pipe but leak still remains. Should I try to pick up a used collector pipe from the bone yard as it sounds like this one is warped or is there some other trick that any of you guys might know about?

I think I am right calling this a collector pipe. It is the unit that holds the cats and all. I don't think you can replace the short section between the manifold and the first cat can you?

 

u checked all your manifold bolts?? doublecheck the rear most ones. those are notorious for breaking, rotting right off. if those are good you might be able to find a exhaust donut gasket. its not really the corrext fix but it might work. another thing.make sure the 2 flange studs are tightned equally so it pulls the flange up to the manifold evenly. those 2 bolts at the bottom where it crosses over. i want to say you can move those up and down for adjustment im not sure.those pipes arent cheap around 200$ beacuse of the cats.

 

I had a camaro at one point and had a similar problem. One of the flanges were bent. I purchased some thick donut gaskets, they were about 1/4" thick. As i tightened down the bolts, it filled in the warped area, kinda like a crush gasket. I think they were made by Mr. Gasket??