Replacing front Y pipes on the exhaust of my S6

I have 136K miles on my 2008 S6. It has the JHM catbacks but has now developed a leak at the Y pipes. I brought it to a muffler shop and they recommended that I replace both left and right Y pipes as well as an oxygen sensor, which will require dropping the engine - work they will not do because they “don’t have the manpower”. I will bring it to an independent shop. I found the OEM Y pipes on sale at My question for the forum is: If I’m going to drop the engine and have to pay for the labor costs, what else should I get done as preventive maintenance? From what I have read in this forum and other sites, I should:

  1. Replace 02 sensors
  2. Check the timing chain and timing chain guides
  3. Check the 4 seals at the back of the engine where the coolant hoses enter.
    Am I missing anything?
    Thank you for your help in this matter.

I’d say that’s a pretty good start. One thing I might be thinking about if I were you would be to possibly move the 02 sensors downstream. I know the Info dump mentions this but I’m not sure if there are any threads that discuss what the process entails. Something worth considering to possibly reduce future maintenance costs. Hopefully some of the other more experienced owners can chime in on this as well.

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Thanks jludt. I remember reading about moving the 02 sensors downstream in the info dump. Not sure how to get that done. Will research further.

if your dropping the motor that would be the time to actually remove the cats. There is more power and the cats over time can be an issue.

The chain and timing guides should be a quick thing but to really look at the full system you would need to remove the transmission.

Check the spark plugs and the seals that seal the top cam carrier. As that can leak and cause a need for a motor pull to change that and reseal that cam carrier.

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As far as I know, the only weak point in those pieces are the flex joint (unless you have a hole in the pipe I cannot see). I would recommend finding a shop that can replace just those pieces.


Thanks justincredible. I’d love to remove the cats but other issuers aside, we have to get emission checks every 2 years here in Wisconsin. Will have the other things checked out if it came to dropping the engine.

Maybe I can save some money. Will look into that. Thanks Illejk!

I’m in PA and here we have to get emission checks every year. JHM can take care of that for you. Like Justin said you’d really be missing out if you keep the cats.

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How much did it cost you to go catless?

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I’ll send the car to the shop on Thursday. Hopefully, as Ed advised, they can just patch up the flex joint without dropping the engine. If not, then will look into all that. Thanks!

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I have the ECU tune and the catbacks. So it will pass emissions without the cats? Or is there some other thing that should be done? Thanks.

If you have the ECU tune already all you have to do I believe is call JHM, let them know, and they’ll send you a new file to get rid of everything.

So was it just flex joints?


Hi Ed. I brought the car to my reliable independent euro mechanic and although he brought in his welding specialist, they did not think a patch on the flex joints would work. I ordered new Y pipes (lot cheaper via, I did my due diligence) about 4 weeks ago - around the time the COVID crisis hit. The parts are still en route/on order. God knows when they will arrive. Will update you guys as soon as I things are right again. Stay safe!

When this happened to me I took it to a custom muffler shop and then replaced just the leaking flex-pipe for about $800.

That looks actaully really good for the work being done with the motor still in. That is the only part that actually goes bad. The flex pipes rot out due to water getting in there and then rust. Other than that the cats get damaged from missfires.

Great job! My muffler guy wanted to drop the engine and replace both y pipes for $$$$. I took it to my regular mechanic and he said he could not replace the flex pipes but could replace the y pipes for much less. Already ordered the parts though. Thanks.

Update: My mechanic replaced both Left and Right Y pipes. He managed to do so without dropping the engine (how on earth did he do that?) so I did not get the 02 sensors replaced, or the cats removed, or any of that other stuff. I just picked the car up today and its running great and the JHM exhaust now sounds just right :slight_smile:
The parts shipped from Germany so it took a while to get here (via
Costs: parts (2 y pipes and 4 gaskets) = $1,346, total cost (with labor) was $1949.38
I guess you have to pay to play!

Crazy as it is, that’s not a bad deal. Dropping the motor is like $2-3k on its own, just because of the labor involved.

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