Exhaust Manifold crack

A

ampico-kid

Senior Member
While I was checking the points on my 30 Coupe, I notice some whitish residue on my exhaust manifold by cylinder #2, just to the right of the bolt on section of the intake manifold. The residue line is about an inch and a half long. When I wiped it away, I could see a crack. There doesn't appear to be an actual opening (yet), and I don't hear anything from it while the car is running. This manifold was a new replacement several years ago. I'm a bit disappointed that it's developed a crack. What is it that might cause something like that to happen? Inferior product? Or just the passage of time and usage?

I understand the danger of exhaust gasses getting into the passenger compartment and intend to replace it ASAP, but just wondering what impact a crack like this could have on the performance of the engine?

Any suggestions as to a good quality replacement?

Thanks. Bob


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I'm not sure it will matter. An original has a head start on development of similar cracks, and the Chinese Foundries are not exactly "on top" of quality control.

Although SOME Chinese product is exemplary. But it's hit or miss.

Your vendor for new can probably tell you more on HIS/her source.

I've told my story of what I first thought was "gasket leaks" but turned out to be a manifold with a series of "hairline cracks" which could only be detected by flooding the top of the hot manifold with oil (and looking for bubbles) while the engine was running and a rag stuffed up the tailpipe. As I removed the manifold and dropped it on the pavement, it broke into at least six pieces - all cracks showing rust in the interstice meaning they've been cracked for a while.

I believe our mentor and frequent reference Vince Falter (fordgarage.com) made a living "negotiating" the quality pitfalls of American/Chinese commerce.

Joe K
 
Did you make sure that the intake manifold was in perfect alignment with the exhaust manifold. If it was slightly proud of the exhaust it would cause a crack like that.
 
You can weld it using nickle rod, here is how. V the crack with a grinding tool and clean up the surrounding area. Heat the manifold to about 600 degrees using your gas grill. Use a stick welder with some nickle rod with the crack in a horizontal position. Peen the weld with a small ball peen hammer as the manifold cools. Don't overdo the peening, just enough to put the weld in slight compression and relieve the tensile forces in the weld.

You can keep the weld as done or grind it flat flush with the surface of the manifold for cosmetic reasons.

It looks like the intake manifold may have been repaired at some point in the past. After the repair mill all the surfaces to clean them up and to make sure that the assembly, when mounted on the engine, does not have any stress. The intake and exhaust manifolds must be in the same flat plane where they mount to the engine.
 
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Chuck Kuntz said:
Did you make sure that the intake manifold was in perfect alignment with the exhaust manifold. If it was slightly proud of the exhaust it would cause a crack like that.
Click to expand...

If the intake was out of alignment, it took about 10 years to cause the crack. Certainly can have it checked before installing the new exhaust manifold.
 
nkaminar said:
You can weld it using nickle rod, here is how. V the crack with a grinding tool and clean up the surrounding area. Heat the manifold to about 600 degrees using your gas grill. Use a stick welder with some nickle rod with the crack in horizontal position. Peen the weld with a small ball peen hammer as the manifold cools. Don't overdo the peening, just enough to put the weld in compression.

You can keep the weld as done or grind it flat flush with the surface of the manifold for cosmetic reasons.
Click to expand...

I'm afraid welding is beyond my skill set. I'm going to just replace it. Thanks for the recommendation.
 
I bought a new exhaust manifold from Bratton's about ten years ago. I had it and the intake machined together. I haven't had a minute's trouble. I do have to torque the manifold bolts regularly, which is probably not related.
 
Most old exhaust manifolds are warped if checked. I purchased a new one from Snyder's and it needed a bit of work to pass my own standards but fit wasn't bad right out of the box. I also installed a new intake but it took more casting clean up to make it look original. Fit was good but the casting needed clean up for more flash than I like to see on a new part.
 
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The crack looks tight, One of mine was cracked like that and it took over 5 years to have the crack open into a leak.
I surface just the exhaust manifold, put it together with the 2 hold the manifold together bolts loose, only tightening them just enough the flatten the lock washers.
The slight gap has not been a problem, actually seems to help with the ethonal gas problem
 
I pulled what I thought was a good exhaust and intake manifold off and accidentally dropped it on the concrete and broke into about ten pieces. After getting over my mad spell I looked the pieces over and both manifolds were cracked almost everywhere it was broken you could tell by the discoloration. I'm so glade I didn't get to use it and have a vacuum leak.
 
definitely don't just buy a new manifold and just bolt it up. The instructions from Snyders clearly detail how the manifolds are not going to fit properly until they're machined. This is a trap many of us have fallen into. Like the other guys have already said, this is likely the cause of the crack.
 
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