Ehaust Manifold Rework - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 4 (permalink) Old 10-14-2015, 09:08 AM
Travesty
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Ehaust Manifold Rework

So I picked up a 2008 Commander Limited with the Hemi last month, and as soon as I got it home off of the trailer I started it up and noticed an exhaust leak. Immediately climbed underneath and found the driver side manifold was leaking. Upon further inspection the next day I found that the lower, rear most stud was broken. I could not believe that I missed this when I initially looked at the vehicle before I purchased it, but it made sense since the leak went away as soon as the engine reached normal operating temperature.

So... I NEVER let anyone work on my vehicles short of paint and body repair, everything else I do myself. But now with kids, 80 hr work week, etc. I farm this repair out. The first two shops didn't want to touch it, said they would have to pull the motor or at least lift it in order to gain access. I told them they were full of it. A friend of mine referred a shop that took it on. I drop the rig off after work, pick it up the next day to the tune of $400 and drive off with no leaks! Hurt, but hey saved me time I didn't have... Wrong.

The next day I had a new leak. I could tell by looking at the manifold to y-pipe connection that it was not reinstalled correctly, but I also notice there was no nut on top of the heat shield where they had just changed to bold out. I started to question whether or not the leak was the manifold flange of header pipe connection. I talked to the shop, they didnt want to correct anything and stated that they didnt check the manifold to see if it is warped, didnt change the gasket, and only changed the stud. I lost it. Who doesnt changed the gasket and check for a warped manifold when chasing an exhaust leak???? I stopped payment through Visa (still dealing with the shop on a refund), and turned around and ordered a new manifold, stainless steal studs, nuts, and a new gasket. I dissasembled the wheel well, pulled 7 studs (1 broke off in 1/8" in the head) then pulled the manifold and blown out gasket. I found that the shop had installed a bolt that was entirely too long, with too short of a grip length. They put a washer and a large nut UNDER the head of the bolt. I was absolutely floored. I have never seen anything like this. Just had to share...

Anyhow I ended up welding a nut to the broken off exhaust stud and backing it out. Coated stainless steel studs and nuts with hi temp copper anti seize and reassembled everything, all is well.

New Magnaflow y pipe and cats arriving today to finish it off.
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post #2 of 4 (permalink) Old 10-15-2015, 10:35 AM
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With the high heat, I worry there is some aspect an ameature hasn't considered when they use bolts of alternate materials. Sometimes its just best to get the OEM bolt from the dealer that is usually a heat treated steel, especially if the OEM has a revised part number meaning they fielded an improved bolt to fix the problem.

Having said that, I've seen some people use Stainless Steel and report it solved their problem on other vehicles.

So let us know if the SS bolts work or end up snapping as well.

Yes, definitely use anti-seize or "Super Hi-Temp Loctite". On other Jeeps, the revised exhaust stud come with "Super Hi-Temp Loctite" already applied. The Hi-Temp Loctite I can never find in the stores, I've had to order it online. Regular Loctites will burn away and be like you used nothing at all.

The idea is too keep the stud from seizing to the head, the Loctite will do that and keep the stud from backing out. Provided it is high temp and doesn't burn away. The anti-seize will keep it from seizing to the head, you might have to tighten them up in the future, but I think it even prevents that in the future. I think when they seize to the head, that sets up a dynamic that eventually snaps the stud, so the anti-seize helps prevent that, I doubt it will be anymore likely to loosen or back out because of the anti-seize.


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post #3 of 4 (permalink) Old 10-27-2015, 08:37 AM
Travesty
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Actually, the use of 304 stainless steel studs was carefully considered for this application. Had Mopar in fact improved the original design of the exhaust studs, that may have been a consideration but no one at the dealer or service department could confirm such an update. Even still, Mopar isnt offering stainless steel hardware so I chose to stay away from their studs. The difference in thermal expansion rates of the steel alloy studs in comparison to the aluminum heads also turned me off, as I have found stainless steel to be much more durable when installed correctly in an aluminum head. The key is copper based anti seize, and a retorque of the hardware after bringing the engine up to operating temp a few times (although I have never found any movement during retorque). I have used stainless steel on turbo chargers, aircraft engines, racing engines, and now Mopar...

Over the weekend I changed out the stock y-pipe and checked the torque on all of the exhaust hardware with no issues at this time. I had the wheel well liners out on both sides for the y-pipe install so decided to check everything, no movement.

Only now I have a new Magnaflow Y Pipe and a new Magnaflow Cat Back that leak at the flange between the two... Trying my best not to weld them but we will see how this pans out. Going back in this weekend with a pre fab piece of copper and high temp RTV.
 
post #4 of 4 (permalink) Old 10-27-2015, 12:32 PM
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Be careful with stainless steel as it is not the way to go in all instances. Stainless steel used in aluminum can be an issue if the studs are not coated correctly as a little moisture combined with the stainless and aluminum will create an electrolysis reaction which will corrode the aluminum over time and the result will be that the threads will pull out. With the heating and cooling and combined with condensation you are asking for a problem some time in the future. Also when stainless steel is repeatedly heated it can harden and become extremely brittle. I would use a grade 8 steel bolts that are zinc or nickel plated.

Last edited by bdalameda; 10-27-2015 at 12:36 PM.
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