Why do exhaust manifolds crack?

[cb7ftw]

Don’t know if it matters, but my reference point is a 99 Civic DX.

Why do exhaust manifolds crack?

Topic

[Grayfox]

+2 on first post and lets not forget it is in the front on most cars so cool air from the radiator also is cooling it down causing it to go through more heat cycles

[dreamer2355]

It depends on the quality of material used plus the heat cycles of the metal will start to fatigue it over time. You also have to think about oxidation due to the elements and engine running conditions. All these can contribute to cracks in the exhaust manifold.

[college man]

A+ on above post. it also has to do with the casting of the part. vibration is another factor. C8-)

[TheArete]

+3 on the Above posts. I agree with all of the above but lets not forget the most pertinent part of the exhaust deterioration… mythical unicorns in the exhaust system. Happens to us all sooner or later, how else do we describe the rapid accelerate

[johnzcarz]

Along the same lines, has anyone had success fixing small cracks in a manifold by brazing?

[outdoorsman310]

I have not brazed a manifold, but i have brazed a patch on a muffler with good success. it would probably be difficult to braze cast

[EricTheCarGuy]

It’s partly a casting issue but also a materials issue. Most manifolds are cast iron which is very good at dealing with heat but by nature it’s porous meaning that there are always imperfections in a casting due to the fact that the exhaust manifold has to go from ambient temp (which could be below freezing) to sometimes as hot as 1200

[Author]

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