Question: Will installing a braided SS flex pipe union in the exhaust pipe pull in enough oxygen to trigger a downstream O2 code?

Background: I recently noticed an exhaust leak at the exhaust manifold to downpipe flange. The flange/pipe is cocked off to the side. I had the downpipe off a couple of years ago and it was straight and tight then (after the reinstallation). The downpipe was and still is rusted solid to the cat. I cut the downpipe in front of the cat and used a 2-1/2” ID pipe union with clamps, which is holding up OK with no leaks.

I’m debating whether or not to take the strain off the exhaust manifold by installing a flex pipe, and if I do I’ll probably just go ahead and replace the cat too. The cat is original and the heat shield all but rusted away. My exhaust is louder than I like and believe that the leak may be contributing to the noise (new muffler). I suppose I could just try tightening it back up (I used anti-seize with SS nuts), but I’m worried about cracking my exhaust manifold in the future. I have/had no O2 related codes.

Edit: I should have added that I recently replaced my motor and trans mounts. Maybe I just answered my concern...less engine movement less exhaust flex.

I found one on eBay: http://www.ebay.com/itm/STAINLESS-ST...97b75d&vxp=mtr

Any thoughts or experience will be appreciated.

 

I have the same issue. If you fix it this way please do let me know how it works out for you. It would be way easier to fix it this way then pull the manifold/intake off and also deal with the 2 precats.

 

local Advance auto sells them.

 

OK, waiting for some input here and another forum.

 

Here anything?

 

I priced the exhaust piping between the manifold to the muffler and it came out to about $120. But mine also has a lot less emissions crap on it, and only 1 o2 sensor. GO RENIX! For exhausts, I say replace things back to stock specs or upgrade. When you start rigging things with inserts and pieces it usually ends badly in the long run.

 

I think it would help, but, i'm in the school of thought that the root cause of the manifold cracking has more to do with the head expanding and contracting. Some will argue this. And they would have valid points too. Bellows in the manifold is a good solution for the expansion and retraction of the head, but the flex pipe or another bellows further down stream like you are implying would help too. Also, the refreshment of your mounts will help...glad to see you took care of that part!

While i replace the manifold on my renix, i'll be doing the mounts, and maybe toss in a flex pipe for the hell of it. Too bad flex pipes are so pricey...well the good ones anyway. I dunno if i would buy one on ebay...i would just buy one from a local muffler shop or parts chain so i could see a few and compare quality-wise before i dropped $60-$100 on something that probably cant be returned...

 

Ryan, I'm sure you've seen the replies here by now. On another forum one guy said he put one on about a year ago and had no problems or codes.

 

Well, while waiting for some input, the next day (patience is not one of my virtues) I decided to at least replace the gasket/seal at the manifold/pipe connection. When the last nut came off the pipe released with a bang. I replaced the gasket but had to use a ratchet strap to bring the pipe close enough to start the nuts.

Since the stress wasn't there when I put it together with the old mounts I'm wondering if the new mounts raised the engine enough to put some stress on the system, anyway I'm probably going to use my angle grinder with a .030 wheel and carefully split the straight pipe union that's on there now and replace it with a new one. Thanks for your thoughts. And BTW I found some locally fairly cheap $20-25 range, just not with the 2-1/2" inside diameter. I just checked online and didn't call to see if they had them.

 

I hear ya and agree, but I worked hard at removing my exhaust pipe, cutting out that damned dent and fitting and welding in a patch. If I knew for certain where to find the pipe without the dent I might just do as you say and replace the whole works with new.

Lurkers: Please spare me your BS about the dent being necessary, unless you can post a scanned copy of a letter from some Chrysler engineer that says it is and why.

 

I remember seeing somewhere that sold that pipe without the stupid dent. Not exactly sure where though. Maybe Rusty's? I know it's a good mod though. I heard it picks up on acceleration because the system is freed up. Nobody knows why they put that stupid dent in. I heard to clear the front axle when the suspension moves, but I also heard that nobody ever had a problem with the two colliding.

 

Thanks. I read about some outfit selling the pipes without the dents a couple of times, but that was after I modified mine, so I didn't bother to make note.

I guess that's just one of those questions (why it's there) that will never be resolved. There was one guy that did mention that he had clearance issues with the front DS and the exhaust pipe, but I've slammed into a few boulders and ruts that have bottomed out my suspension hard and there's not a hint of a scratch on my homemade patch.

 

Ryan, I found a 10" flex pipe (2-1/2" ID) at Auto Zone for about $28. I installed it and now my exhaust pipe is aligned perfectly with the manifold and there is no stress from the misaligned parts.

It may well be true that the cracking is related to the relatively thin manifold pipes expanding and contracting from the extreme heat...but I feel better.

 

Glad you solved it

 

Nice work on the patch and flex pipe! I recall reading somewhere that the dent is deliberately there to increase exhaust temperatures so that the cat heats up faster