Exhaust manifold connection to catalytic converter pipe leak
Hi guys, I have an exhaust leak that I was looking for some opinions on how to fix. I had Banks Torque Tubes installed on the truck about 4 or 5 years ago that developed several cracks on the collector welds. They had to come of so I went back to the stock manifold that fortunately I had kept. About 15 hours later (manifold/headers on the 5.4L are no fun at all) and I have a leak at the ball joint connection between the manifold and the catalytic converter downpipe.
I have taken it apart many times and tried repositioning things in numerous ways just to try and get the joint to seal up but it still leaks. Visually looking at the two mating surfaces they look fine, no rough or rust pitted surfaces, smooth, round, no obvious dents. But it still leaks. I was hesitant to try and reshape the mating surface with a hammer because I do not see any obvious out of round areas.
Could I put any type of exhaust flange gasket or donut gasket in that joint? Stock configuration is no gasket, just metal on metal. I am afraid if she goes back into the dealership they are going to want to put a new catalytic/downpipe on it. That part from Ford is upward of $900.