LR Audi

I recently replaced the passenger-side catalytic converter on my vehicle. I have the 2.8 30V engine. There are five fasteners to remove. At the rear of the car are two 17mm nuts to need to be removed to unfasten the clamp that attached the catalytic converter to the intermediate pipe/resonator/mufflers. At the front are three 13mm nuts that attach the catalytic converter to the exhaust manifold. Two of the three nuts are accessible from the buttom and are relatively easy to get to. The third is acccessible only from the top and is a challenge to remove and reinstall.

First step is to secure your vehicle on jack stands. You don't need to jack up the entire car, although if you do you have more room in the back to remove the exhaust clamp. Try to jack the vehicle up as high as possible. In pic 1 you'll see how I have four jack stands on the front of the vehicle just to be extra safe. You must remove the front wheel for better access.

Second step is to remove the air intake housing and assembly. This will allow you to have access to the incredibly difficult top nut. You have to disconnect the sensors. Do not lose the securing clip. Remove everything from the intake box all the way to the plastic elbow before the throttle body. In pic 2 you'll see partial disassembly.

The third step is to remove the wiring block that holds various electrical connectors. These are 8mm nuts. They are best accessed with a 1/4 inch drive ratchet. In pic 3 you'll see I use an air ratchet. Air tools make the job so much easier. Once you remove the wiring block from the firewall you can move it aside and reach down remove the top nut. I used a 3/8 inch drive ratchet with a shallow 13mm socket for the top nut. You can use a 1/4 inch drive ratchet but you won't get the leverage you need.

The fourth step is to remove the lower two nuts on the catalytic converter. You can easily access them with the front wheel removed. In pic 4 I have them both clearly removed.

The fifth step is to remove the exhaust clamp in the rear. This is secured with two 17mm nuts and they just zip right off with an impact. You may need to use a 1/2 inch drive ratchet if you don't have an impact. These are torqued down really well. Once these nuts are off you can take a rubber mallet and tap the clamp until it comes loose. Then wiggle the old catalytic converter until it is just hanging.

The sixth step is to disconnect the O2 sensors. On the wiring block, the third connector from the left is the front O2 sensor. Disconnect this. Right after the cat is the rear O2 sensor. You can cut the wires several cm past the O2 sensor itself. Now you can wiggle the entire catalytic converter out of the vehicle. Use a 7/8 inch O2 sensor socket to remove the old O2 sensors and place into the new catalytic converter. Or you can take this opportunity to replace your O2 sensors if you need to.

Reinstallation is the reverse order. Overall this job took me a lot longer than I expected but I saved well over $800 doing this on my own. The catalytic converter was an aftermarket catalytic converter. It cost $200 as compared to the OEM which was $700. In pic 5 you can see the difference between the two.

RobertA6

Thanks for the info man, i was thinking to do the same as well, i will let you know how it goes.

Keep up the great work.

LR Audi

Replaced both sides for about $400. Threw in new Bosch O2 post-cat O2 sensors for $180 and O2 sensor spacers for $50. One catalytic converter from OpenRoad Audi by itself is $1,800 so I saved myself a ton. I also replaced the nuts that hold the cats to the exhaust manifold, and surprisingly each nut cost me $5 for a total of $30! For six bloody nuts! Three hours of busted knuckles saved me a crapload of money towards another repair. This car'll last forever.

halo777

Nice work!

LR Audi

Thanks, good to see that despite many who read my posts a few recognize my efforts. I eventually did the driver-side catalytic converter as well, and accessibility was much easier when I moved the coolant reservoir out of the way. One thing I must mention is that the original Audi cats are much higher quality and have a different flow rate, so using O2 sensors is a must with any aftermarket cat.

kjopen

I know this is an old thread however, these steps are really helpful as I'm finally going to bite the bullet and replace my cats - I've had two sets of flexible couplers welded in over the last few year and now the cats are beyond their life... I've had the check engine on for two years....P0421 & P0431 codes.

Thank you.

LR Audi

You're very welcome. I haven't been on here in years but it's great to see that people can still benefit from my work. I no longer have my A6 though. I dumped so much money into that car, it was the biggest money pit I've ever owned. I fixed it up after spending more on it than what it was worth, and then I came across a deal of a lifetime so I sold it to someone in Calgary. I've been driving a 2009 S8. The V10 sounds awesome, and while it doesn't have the torque of the newer 4.0 V8 biturbo, it has is truly unique being a 10 cylinder car.

I recommend getting a Vag Com if you don't have one already, I've had mine for years and it's paid for itself over and over.

kjopen

Yes, I have a VAG COM and know what the codes are, they are right as the cats are below threshold - I've just been putting it off and having the blown flexi coils replaced as they were leaking.

Now after 17 years on the car and 240klms they need replacing so I can sell it on. I also have an A4 that needs a new cat (1.8 turbo).

Nice to hear of your S8 - sounds awesome, my son has an S4 that he loves... I'm thinking of an S6 next but need to shift some of my old cars on as my drive is full! (I've also got an 87' Jaguar XJS!)

LR Audi

I had 330,000km on my A6 when I sold it. I dumped so much money into that car, it was the worst vehicle I owned and nearly turned me away from Audi in general. After I did all the motor work, I did body work and paint to bring it up to the way it should have been. I installed a Sarona body kit, which I do not recommend as the panels fit was poor and construction quality was sub-standard compared to OEM. I eventually supercharged it, with an Eaton-based PES Supercharger I bought used off eBay. Only after dumping more money into than what it was worth, which was a really stupid emotional decision, I actually started to enjoy it. Then I purchased this S8 from Florida, in absolutely mint condition at a price no sane man could pass up. I recently learned that PES also has a Whipple based supercharger for this engine, but it's performance is good enough for me. It won't handle like an RS4 or pull like an R8 because it isn't meant to, but it fits me comfortably.

My neighbour has a B8 S4 as well. While I do appreciate those cars, I could not own one as I am a large individual (ask Tarpan or Jamie, they've both met me) so an A6 is the smallest vehicle I can get into.

I hope you keep your Jaguar XJS! Just before my S8 purchase, I was looking at Jaguars and drove the X351 Jaguar XJ. While it had a better fit and finish than even my S8, it lacked soul and character. I miss the old generation Jaguars that had true English roots, with style and class. We can thank Ford for screwing up Jaguar just like we can thank GM for destroying Saab.

I never drove an S6, but if you get the one with the same V10 motor as me then it will be a damn hoot to drive. More nimble, less weight and same motor makes it a beast!

Good luck on your cats, I hope to see you on the road some time.

kjopen

My A6 is coming up to 240,000klm so have been lucky the cats lasted this long! The bodywork is still mint and although I've had a lot of work done by Audi in the past, I'm now using it as a second car and doing any work myself as I now have the time. I just don't want to sell it for nothing - I'd rather run it into the ground, but it's an Audi and just keeps going

I'd really like an S8 though... - you've got me thinking now

The Jag is an 'always wanted car', or at least the V12 I should say, can be daunting to work on at first but the pleasure of working on a V12 is awesome and the raw power is something special.

Take care friend