On a diesel tractor, the exhaust manifold has developed two holes, possibly from thin castings, and possibly from rust. The manifold is cast iron, and I would like to patch it. A local farmer tried high temperature epoxy. That lasted until the manifold got real hot when plowing.
So I am thinking brazing. Specifically, I am thinking of putting a nickle/copper patch in place (a part of a nickle coin) and brazing it in place with bronze brazing rod, using an oxyacetylene torch. Preheating to 400F and then post heat at 400F, with a gradual cooldown to minimize the possibility of cracking.
Has anyone tried anything like this? Suggestions?