Manifold crack :[

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DuckSauce1098
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Joined: Mon May 24, 2021 2:48 pm

Manifold crack :[

Postby DuckSauce1098 » Thu May 27, 2021 6:22 am

So my new to me 2008 Pathy with the VK56 has a very slight manifold crack. I didn't even notice it when I went and looked at truck. You cant hear it idling or if you drive with the windows up. Under moderate acceleration though its absolutely there. It sounded like a bad collector gasket but I cant find anything downstream. It sounds like its only the passenger side currently but I think its smart to just replace both. Now, I have questions, and I'm sorry if I'm beating a dead horse.

How common was this on the R51? I know the Titan and Armada suffered from this often.

Where exactly do the cracks happen, or are they totally random? All those heatshields make it hard to find.

Go with OEM for replacement parts? I've found aftermarket ones floating around eBAy, Rockauto, ect, for ~$500 for the pair. Does anyone have any experience using them?

Finally, has anyone tackled this in their driveway? I've seen plenty of Titan replacements, but never an R51. It looks like the front pumpkin and axles have to come out because there isn't a ton of room there. Are manifold studs common to snap off?

I was a former Audi tech for years, so I'm loaded with tools and I'm no stranger to shit jobs.


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smj999smj
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Re: Manifold crack :[

Postby smj999smj » Fri May 28, 2021 9:06 pm

V8's are pretty rare on the whole of the R51 production, so rather than say it's not common on R51's, it would be more accurate to say it is a common problem on the VK56DE engine, regardless of application. I wouldn't say that the aftermarket versions are any worse nor any better than the OE manifolds from Nissan. The best fix as far as reliability and prevention seems to be going with long-tube headers, however, that requires getting UpRev to reprogram the ECM with a custom tune so that (1) it will not cause a lean running condition and (2) it will keep the catalyst efficiency code from triggering, causing the CEL to come "on." Cajun B Pipes makes packages for the Titan/Armada, but I've heard it can be fitted to the R51, as well:

https://www.cajunbpipes.com/

I believe Doug Thorley makes headers for them, as well. I'm not sure how much more difficult headers are on the R51 V8 compared to the V6, but the V6 is best done by removing the front wheels and the wheel well liners, which expose the exhaust manifolds on the side of the engine. I suppose one could do it on the ground, but having a lift makes it a LOT easier! Cracks seem to develop all over the factory manifolds, including on or between the runners and even on the flanges, sometimes. The studs are beefy at 10MM and usually do not break.

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DuckSauce1098
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Re: Manifold crack :[

Postby DuckSauce1098 » Sat May 29, 2021 5:02 am

Thanks for the reply! It makes me feel a little better about the studs as that's my main concern. According to ShopKey I'm supposed to drop the crossmember and remove the front diff to remove these things. It sure looks cramped in there so I think this might be accurate.


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