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Weld a cracked exhaust manifold?

I just had to replace an oxygen sensor in my 2000 Honda Civic LX and upon the mechanic replacing the sensor they discovered a crack in the exhaust manifold. I know that this year and model Civic has had issues with the exhaust manifold cracking but my car has 106,000 miles on it so it’s not covered. The crack actually originates from the hole the sensor is screwed into so I have some suspicions as to whether the removal of the bad sensor caused the crack. In any case, is it possible to weld a crack on an exhaust manifold or is that just not done? If it is done, how long could I expect the weld to hold?

You can weld cast iron with the proper welding rod and technics. But for this application it won’t work. Because of the expansion and contraction of the exhaust manifold from being heated up and cooled down, the weld would fail.

If welding exhaust manifolds worked, that’s what I would be doing. But I replace them instead.


Find a junk yard exhaust manifold, with a guarantee of no cracks of course. Don’t bother having it welded.

Cracks in the exhaust manifold are a common and known problem in this model.
Junkyards will either have manifolds with the same problem or any good ones will be long gone.

Replace with a new updated style for the guaranteed fix. Leaking exhaust is nothing to take lightly.