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Thread: Cracked header, again... Rinse and repeat!

  1. #1
    JTS Host Tony's Avatar
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    Cracked header, again... Rinse and repeat!

    Why is it that the Jeep Cherokee keep cracking the exhaust manifold? I've been through three(?) now.

    I just ordered this one from Amazon

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    The common things people say that cause a cracked exhaust manifold, or in the case of my last two, exhaust headers, is physical stress. Usually bad motor mounts or transmission mount.

    Now it is true I haven't had the Brown Dog motor mounts the entire time I have had this manifold, I have had them for awhile.

    A friend of mine suggested that the reason for the crack(s) could be the rapid cooling when I've driven in high water. I do enjoy driving in high water. Not of the 6 foot variety but six inches up to two feet sure!

    Now I've been wanting to get a mig welder and learn me how to stick two pieces of metal together for a long time now. Certainly welding up my old header would be a good thing to do, but now I want to change the design a bit.

    I wonder if I put more metal around the area prone to cracking if this would help in the event of rapid cooling.

    I have also seen where people have placed flexible exhaust hose between the collector of the manifold and the down pipe. Certainly this would address the stress issue.

    I have also seen long bolts with springs that are using to bolt the exhaust flange from the down pipe to the header. The idea is that it allows the down pipe to move on the exhaust flange "dough nut" as needed.

    Does anyone have this issue with cracked exhaust manifolds on the TJ? YJ?

    Maybe you know why they crack, please share if you do!

  2. #2
    JTS Contributor 4.3LXJ's Avatar
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    I think the reason they crack is that they are a six tube header. On the newer 4.0s that have the split header I haven't heard of this being a problem. I think it is just too much expansion and contracting of metal from temp change. You might put out a feeler on the split header cracking

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  4. #3
    Junior Member tacklebox's Avatar
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    I did just that! Soon as I noticed a small leak / crack I broke out the MIG. Fixed the leak and ran a bead anywhere I could near the collector. Been running it pretty hard for the last 6 months that way with no new problems. Frankly it has lasted longer than I figured it would but hey.... what ever works.

  5. #4
    Junior Member 89limited_hero's Avatar
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    Besides our beloved 4.0L the ford 300/4.9L always had the same issue with cracked exhaust manifolds. Early models were cast manifolds before their fix of a tubular manifold. Which like our 4.0L didn't hold up either. Sorry random useless info. Lol

    I have the same problem and have a stock back up which is almost cracked but not too bad. Was wondering if putting some of the header wrap tape the high temp fabric stuff. Would help with the manifold cracking as well turning the under hood temps down some?

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  7. #5
    JTS Contributor 4.3LXJ's Avatar
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    I don't think so Josh. My take on that cracking header is that the thing is too long and expansion and contraction from temp differences is what eventually does them in. I say this because the 00 and 01 header doesn't seem to have this problem. It is a dual pipe header as opposed to a single pipe for the rest.

  8. #6
    Junior Member 89limited_hero's Avatar
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    I get what your says and make sense guess there is no way around making the early model header not prone to cracking without exhaust work and swapping parts.

  9. #7
    JTS Contributor 4.3LXJ's Avatar
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    I don't see any reason why you cannot go to the split header pipe. In theory, that would give you a little better low end according to old hot rodders

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