Manifold Burn Through

Steve@Advance · Jul 12, 2017

Below, there was a question about an Allis with idle problems.

One thing I suggested he check was for a burned through exhaust manifold leaking internally into the intake.

Got to thinking, how would you check for that?

Only way I can think of would be to remove the manifold, cap the exhaust or intake, lay it on it's side and fill it with liquid, watch for it to leak.

Any other, simpler tricks of the trade anyone can think of?

Janicholson · Jul 12, 2017

Looking down the exhaust pipe with a fiber optic. Jim

old · Jul 12, 2017

Intake suction would be a lot different and one could feel a push pull if one held there hand over the air intake of the carb

Charlie M · Jul 13, 2017

The holes in manifolds that have happened to me have been leaking through to the outside and I could either see them or feel them if I ran a hand over the hole. I've had manifold gaskets go bad but they have been on the exhaust side and I could see the exhaust coming from the leak.

Dan in North Houston · Jul 13, 2017

Many years ago somebody challenged the readers of this site to figure out the problem of a tractor with some unusual symptoms. It was an 8N as I recall, and it would start normally but almost immediately die. I don't remember the details, but I believe there was some coughing and puffs of smoke involved. There was a long list of what had been done, checked, adjusted, and people spent several days guessing what was the problem. It turned out that there was a hole in the manifold between the intake and the exhaust. The tractor would start normally, but the resulting exhaust stream would then enter the intake and kill it. A new manifold cured the problem.
You can get a fiber optic endoscope for your PC off of e bay for about $15 that would let you see inside the manifold.

jeffcat · Jul 13, 2017

OK give this a try. If you don't mind unhooking the fan belt. Start the unit and have a bottle of baby powder handy. Just a gentle dusting should let you see any blow outs and suck ins should also be seen. Between them the endoscope sounds good. Old toys do break. Done it a couple of times at work trying to find gasket leaks in large ovens.

ss55 · Jul 13, 2017

Intake vacuum gauge.

Dick L · Jul 13, 2017

I just used my hand a rag and an air hose. Core shift will cause them to fail early.
After I could hear and feel the air come out the exhaust while blowing into the carburetor with a piece of cardboard between the head and manifold I cut up the manifold to see where the problem was.

fixerupper · Jul 13, 2017

Dick, I'll betcha it ran better with a new manifold. I wonder how many years it took to plug that bad.

Steve@Advance · Jul 13, 2017

Thanks everyone.

Got to thinking, the easiest way to simulate a burned out manifold would be to trick the EGR valve into opening on a car engine.

Went Youtube prowling, found a video for diagnosing an EGR problem. He put a vacuum gauge on the engine, holding steady at about 18". Then opened the EGR, the vacuum dropped drastically to around 5"!

So, looks like a vacuum gauge would catch it, even if it were a small leak.

Thanks again!

Manifold Burn Through

Steve@Advance

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Janicholson

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old

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Charlie M

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Dan in North Houston

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jeffcat

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ss55

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Dick L

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fixerupper

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Steve@Advance

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