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Exhaust mani leak on 88 4.0 Renix


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Well now that I have the 88 4.0 MJ on the road with the new cat/muffler, I hear the ticketty tick of an exhaust manifold leak. What should my next move be? Gasket? Or what is the method for finding the leak or crack? If it turns out to be the Mani what is the most opted for manifold or header? And also what all has to come off to replace?

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It's likely either going to be a loose manifold bolt causing the leak, or a crack. Re-torque the bolts and inspect for cracks. Cracks are very common though.

 

What I did for my 88 is found a manifold at the junkyard with no cracks, but long story short I sold the truck before I replaced it. If you want a new part this is a good option http://www.amazon.com/gp/product/B000C123A2/

 

If you're looking for a manifold, easiest bolt-on replacement is the 87-90 one. The 91+ are different.

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Tickity, tick.  Don't forget to check your EGR tube nuts.  Those things loosen up over the years at both ends.  Only then would I replace the manifold gasket using Permatex spray copper.  And while the manifold was hanging I would refinish the EGR tube seats.

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I also had a leak and replaced the manifold gasket which was bad.

 

Then about two years later I had another leak and thought it was the gasket again but turned out to be a small crack on the manifold I was unable to see unless I took it off. I then got the manifold welded since it was a small crack. Id also suggest doing the garden hose trick which is just taking a small piece of hose with one end by your ear and moving the other end around different spots by the manifold. Wherever you hear the loudest sound is where your issue is located. The hose is acting as a stethoscope...

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I also had a leak and replaced the manifold gasket which was bad.

 

Then about two years later I had another leak and thought it was the gasket again but turned out to be a small crack on the manifold I was unable to see unless I took it off. I then got the manifold welded since it was a small crack. Id also suggest doing the garden hose trick which is just taking a small piece of hose with one end by your ear and moving the other end around different spots by the manifold. Wherever you hear the loudest sound is where your issue is located. The hose is acting as a stethoscope...

More great information! Thanks, 1989 Eliminator!
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