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Thread: Jeep 4.0 Cracked Manifold

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    Default Jeep 4.0 Cracked Manifold



    This winter I need to do something about my cracked exhaust manifold on my 99 TJ. I cant quite get eyes on the crack, but listening around with a hose i'm pretty sure its the manifold.

    I'm curious if anyone could share their experience with the cheap ebay/amazon-grade manifolds, the parts-store grade units (Dorman, Omix-Ada) or attempting a weld/braze repair. Thanks.

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    Default Re: Jeep 4.0 Cracked Manifold



    No helpful answers from me but I started down this same path 18 months ago. Turns out the bolts holding the header to the engine were loose on mine. I'm interested in what you discover and how you fix it.

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    Trevor? (November 7th, 2021)

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    Default Re: Jeep 4.0 Cracked Manifold



    Interesting. I'll double check before ordering anything. Thanks.

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    Default Re: Jeep 4.0 Cracked Manifold



    I'm doing something similar, I have a sound like a slight leak when it's cold that goes away when warm. I think it's the connection from the manifold to the pipes, if you lay under the driver's side with a long extension it's supposed to be easy, I'll see...

    Found this too:


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    Trevor? (December 10th, 2021)

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    Default Re: Jeep 4.0 Cracked Manifold



    Took me a while to find my crack without disassembling everything, but it was at the main collector. This is on a 96 XJ, 4.0, stock manifolds. Not sure what type of manifolds you have on yours....

    https://drive.google.com/file/d/1oE8...ew?usp=sharing (link to my personal google drive for a photo)

    I ended up cleaning and welding it. It seems to be consensus that the cracks happen as a result of worn out motor/trans mounts (can't guarantee that to always be the case though). I replaced both of those mounts at the same time as welding it. I have not yet checked to see if the fix is still working as I don't have many miles since doing so.

    I have also been considering aftermarket headers, but hear just as many cracking stories as stock manifolds. I'd likely take a gamble on the Pacesetter headers if I had to replace right now....Dorman replacement would be a close 2nd if I wanted it to be a quick swap.

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    Trevor? (December 10th, 2021)

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    Default Re: Jeep 4.0 Cracked Manifold



    Gearwhine previously posted:
    "I ended up cleaning and welding it. It seems to be consensus that the cracks happen as a result of worn out motor/trans mounts (can't guarantee that to always be the case though). I replaced both of those mounts at the same time as welding it. I have not yet checked to see if the fix is still working as I don't have many miles since doing so."

    Seems feasible. At least in my Jeep there seems to be very little flex in the exhaust itself. If the engine were flopping around I could see that fatiguing the metal in there.

    I ended up buying an inexpensive new manifold on Rock Auto. The brand is SKP. If I get a break from work over the holidays then I should have the time to install it. Based on this input I'll be sure to get a good look at the motor mounts too while I'm in there.

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