2006 QX56 exhaust manifold/headers

[jkehl2003]

I have a 2006 QX 56 that has a cracked passenger side exhaust manifold. Anyone else been through this? Did you replace with a new manifold or put headers on? I was looking at the Stillen Stainless headers, anyone have these? Pros, Cons?

[C-Kwik]

Its a fairly common problem on earlier QX56/Titans/Armadas. The manifold flange has a relief cut between the 3rd and 4th cylinders on each bank leaving the 4th runner to have to support any load placed on it by itself. Speculation is that the weight of the exhaust pulls on this too hard causing failure. Both manifolds on my Titan failed between the 3rd and 4th cylinders of each bank and both showed signs that the last runner had been pulled down and away. My understanding is that new manifolds were updated with thicker walls in the area of failure to resist the cracking.

I fixed mine simply by having a muffler shop weld them back up. They are made of what looks like two pieces of stamped steel that are welded together so it should take to welding pretty well (unlike cast manifolds). Time will tell if it ends up holding or not, but it was a $40 fix for me. It is a lot of work to remove and install though so it will suck to have to do that all over again if it does fail, but worth the attempt as I'd prefer not to use my financial aid to pay to fix it.

As for Stillen headers, the obvious pros and cons are more power, louder exhaust, and lack of catalytic converters. Whether these fall into the pro or con list depends on you. One option I'll be exploring if the welds don't hold will be JBA shorty headers with the existing cats welded on. The downside there is that eventually the cats will wear out and I'd have to buy new manifolds to get new cats anyways. I don't trust aftermarket cats enough to go that route.

[iNfinitiNBeYond]

Had mine replaced too... 4K to 5K of work... In good with Infiniti personel without warranty she did a comP... yes Free.. man... I guess it wud of leak into your air vents..... hmmm.. CO poison..

Well, I would stick with the infiniti manufactured parts that way it is covered under their warranty if any...though stillen brand would be awsome, might as well go with the super charge stillen then...

[jkehl2003]

Well.. I have the QX up on a lift right now with new Stillen SS headers on it. Wiring up the O2 sensor box tomorrow and we'll see how she purrs. I already had Dynomax exhaust, so I'm hoping this doesn't make it too much louder.

[Timmbo]

I am very interested in hearing what your thoughts are of the Stillen headers, that does sound pretty sweet!

[DTM]

Same issue of cracked manifold and also interested in Stillen headers to replace manifolds. I contact Infinity customer support and was told that there is no warranty extension for this failure.

[jkehl2003]

The headers sound really good. A bit loud in the cabin at certain RPM's, but sounds really good if you have your foot in it.. It seems to have a bit better throttle response, but not sure if I can say there's a noticeable HP difference.

[Socaldiablo]

I hadn't heard about this. How do I check if mine is cracked or failing? I have an 04' QX56. Is it visible from the engine bay or underneath the truck? I'd like to check. Yikes ....$4-5K worth of repairs for this would mean a very grumpy Christmas.

[jkehl2003]

Mine was a very noticeable exhaust leak when starting and accelerating.

[Socaldiablo]

Mine was a very noticeable exhaust leak when starting and accelerating.

When you say noticeable exhaust leak, did you start smelling exhaust fumes in the cabin? Not sure what you mean. Obviously, exhaust fumes are invisible and so a noticeable leak could mean the smell in the cabin. If mine was failing, would I be able to see stress cracks in the manifold and if so, what is the best vantage point? From the engine bay or from underneath? I had planned on upgrading my exhaust system from the cat back at some point in the upcoming handful of months but with hearing about this, I may just do like you all and purchase the Stillen manifolds & the Stillen exhaust system and have my muffler guy do it all at the same time.

[jkehl2003]

You could hear the leak. Under acceleration it sounded like the engine was ticking.

[C-Kwik]

Generally, you will hear a leak. Its easiest to hear with the windows down while accelerating next to a wall. It will be a clicking noise like mentioned above. You may also feel a slight degradation in performance, gas mileage and shifting quality.

Visually checking it will require removal of the heat shields, which are not easy to remove. Cracks usually occur between the 3rd and 4th cylinders on either side.

[Socaldiablo]

Is this something that I should proactively replace or does it make sense to just take care of it if it happens to my truck? If I wait until it happens, would it cause other damage or cost more to repair than if I replace this now? Someone on eBay has the passenger side manifold for sale (new) and it's the new part no., not the original part no. It was at $305 last night (if anyone is interested). I will, however, go with the Stillen set-up if I need to replace this. One concern with the Stillen is since that set-up has no cats, will I pass smog certs? I live in a city where this is required almost yearly.

[C-Kwik]

Its unlikely any collateral damage will occur from a cracked manifold. Its just a repair as needed. As for smog, you will definitely fail any legitimate test in CA. Even assuming you can get passed the visual and the OBDII connection, your actual emissions will likely be over the limit.