While inspecting the engine today, found a bolt that holds the exhaust manifold on had broken off. It had been that way for some time since it was rusted and discolored at the location of the break. Then to my dismay, I saw a crack in the exhaust manifold. Hard to tell how long it had been there. Anyone experienced this? Is there an aftermarket exhaust manifold that is split? Talking to some Cummins people, this is a common problem on the 5.9. The expansion and contraction of the manifold set up stresses that cause the crack. Unfortunately, this is way beyond my skill level as well as Tere's. It all is turning into a real nightmare.

YES, this is a problem with most 5.9L Cummins at some point in their life. Mine was cracked when I bought it and it was bad enough that some of the carbon laden smoke made its way up to the bedroom.

This is caused by the tremendous heat range these things go thru.

Example, when you climb a grade and go to maximum EGT, it is not unusual to get gases around 1250 degrees. Then when going over the top of the grade and down the other side, the exhaust gas will be virtually cold in no time at all.

You will find most cracked manifolds are shorter than the new ones by 1/8 inch or more. In my case, the manifold had shrunk until it was binding end bolts

This is not a really big job! The bolts will come out fairly easily. You will have 12 bolts holding the manifold to the engine head and 4 to the turbo. Plan in advance and soak the crap out of them with a got penetrate (kroil or equiv)and make sure to get new bolts and gaskets.

Ed, did you replace yours with a Cummins factory replacement or an aftermarket? I'm looking at some split manifolds which might work. As far as the job goes, I can turn the bolts. But if I break one off, that's when I am in trouble since I have no experience drilling out a bolt and cutting new threads. Did you break any bolts while doing yours? Also, I don't think it's leaking exhaust yet. Should I just wait until it is?
Thanks
Jim

Just get it fixed; if you're not comfortable doing it, take it to a shop. As Ed says, it's no big deal - shops deal with it almost daily.

I replaced it with Cummins OEM part. The new manifold was noticeably different. I didn't like the left over casting slag and cleaned this off with a die grinder.

Exhaust manifold replacement

I have 125K miles on this one and not cracked but it also is getting shorter. I don't think it will be a problem for awhile.

None of the bolts were broken or broke while removal. One trick to use is to run the engine to heat up the manifold and head, then shut down and loosen all the bolts a turn or two. Let it cool and complete the removal.

Is bolt that is broken on yours long enough to get a good vice grip or small pipe wrench on it?

I hope that bolt isn't broken off flush with the head!

If it is not leaking I would not touch it yet. These will go a long time even cracked.

Got any pictures?

Had this happen about five years ago. My mechanic did the job for a really reasonable price.