Rust on the Exhaust Header Manifold

A good welding shop should be able to use the correct technique, I’d think.

Could be 409 stainless. It’s used for automotive exhausts and is weldable without heat treatment.

Could be, could be. Nevada may be right that it’s a type of SS.

how can you tell?

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If the only problem is rust, then nothing needs to be done. My Corolla’s exhaust manifold looks just like that. It’s been working fine for nearly 30 years. If the exhaust manifold has a crack in it though, then it needs to be replaced or repaired. A crack will allow outside air into the exhaust stream and will confuse the engine computer when it read the signal from the O2 sensor. Do you see that thing poking from the exhaust manifold surface with the wire on it? For the engine to run properly you can’t have any air leaks prior to that.

If my car had a cracked manifold I wouldn’t attempt a repair, too risky. I’d just install a replacement manifold. I’d try to find one at a junkyard , if I could find a good used one from a wrecked car, it wouldn’t be overly expensive.

I just did a search in google maps near me, found a few, I’d drop by and ask three of them for an estimate.

No, no… you said the patch had failed. How did you come to that conclusion? I’m curious.

Because you can clearly see the crack in the picture, a crack that presumably had previously been filled with whatever silver stuff is around it. Zoom in on the middle of the manifold.

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I had a friend that was a commercial welder for 45 tears, he ad done pipeline, fabrication, steel building frames and commercial welding shop work. He also worked on cats in his spare time. He told me that a proper;y welded manifold was better that a used uncracked one. He always welded as much of the crack as he could on the car because he said the crack relieved the stress caused by the heat warpage and leaving it bolted in during welding made it fit flatter.

Like a lot of my friends, he is gone now. Most of them, I thought would outlive me.

Because you can see it in the picture
Capture

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It’s not my picture, and the picture doesn’t prove the patch has failed. Testing is required. There was no mention of exhaust gases leaking by the mechanic. He had only mentioned “rust”. I’d leave it alone. Sound like the mechanic is trying to upsell based on a non-existent issue (the patch seems like a coincidence).

That is a textbook photograph of a failed patch. How much it’s leaking, I don’t know.

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I’m generally in agreement with you that you don’t have to automatically replace when there’s a crack.

But the patch has failed. You can see the crack. If you can see the crack, the patch has failed.

That doesn’t necessarily mean the header is leaking, because if your engine is running a little rich, unburned combustion products (soot) can get into the crack and actually seal it off, but that doesn’t mean the patch is successful. And it also doesn’t mean that soot will stay there permanently.

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I believe I’d find someone to weld ‘er up for $100 bucks or so and be done with it. I’d pass on buying the whole new assembly with converter and all.

It’s a stress fracture. The gap is clearly visible. If it wasn’t leaking, why would someone try a half-butted repair? The patch failed because it fell off. Stress cracks never get better on their own. The time to fix it right is when you notice it, before it gets any bigger. This one is headed for the O2 sensor boss. When it gets there, the repair gets much harder to do. This one is text book easy now.

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