1999 Infinity QX4 Catalytic Converter/Exhaust Manifold Join

Tiny
LASERJOE100
  • MEMBER
  • 1999 INFINITI INFINITY QX4
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 236,000 MILES
Just changed both exhaust manifolds, and front pipes.

The joint between the cat converters and the manifolds
both leak badly, even with new converter caps and wire washers. BAD! Now I'm told that the cat converters should have been changed at the same time because it's impossible to get a good seal between the new Manifolds and the old CC's. True? Too late to change the cats now since the manifolds have already been run hot, so?
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Friday, August 6th, 2010 AT 9:21 PM

5 Replies

Tiny
MHPAUTOS
  • EXPERT
Hi there,

Thank you for the donation,

Are these a flat flange type bolt up system?

Mark (mhpautos)
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Saturday, August 7th, 2010 AT 12:22 AM
Tiny
LASERJOE100
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Yup. Flange with a lip that interlocks with the manifold. There is also a "wire washer", and a cap, which is a hollow ring that covers the wire washer, that act similar to giant "o" rings within the cats. Leaking like heck!

The theory was that because the manifolds are new, and the cats are old, they may not ever be able to seal because the did not warp together. But that doesn't seem right to me, because that would mean that every time a manifold got changed, the cat would have to change, too.
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Saturday, August 7th, 2010 AT 12:42 AM
Tiny
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I would be thinking the flange on the cat is warped from manufacturer, I have seen this a few times, check with a straight edge.

Mark (mhpautos)
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Saturday, August 7th, 2010 AT 7:15 AM
Tiny
LASERJOE100
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That's probably not the case, since BOTH manifold/cat connections are leaking. In any case, the mechanic is claiming that the cats (not replaced) and the manifolds (new) would never give a perfect seal simply because the old cats would be slightly warped just due to regular use. That doesn't seem to me to make sense, since that would mean that one would ALWAYS have to replace cats along with manifolds to get a perfect seal. Besides, shouldn't the wire washer/caps take care of this by acting as a gasket?
The short question is: should I be able to get a tight seal using the old cats along with new manifolds? Is this a common problem? Thnx.
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Saturday, August 7th, 2010 AT 7:42 AM
Tiny
MHPAUTOS
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There should be no reason not to be able to get a gas tight seal with old cats and new manifolds.

Mark (mhpautos)
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Saturday, August 7th, 2010 AT 7:50 AM

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