S5 NOx Catalyst Trouble: Exhaust Leak Insight Needed

Had a similar situation with my 2016 Audi S4. The exhaust system issues started with minor leaks around the manifold gaskets, but car diagnostics revealed more significant problems with the NOx catalyst system. The symptoms matched exactly, check engine light, exhaust noise, and catalyst-related codes. Initial inspection revealed cracks in the exhaust manifold and deterioration of the NOx catalyst, likely due to prolonged exposure to high temperatures and normal wear. The exhaust system needed comprehensive work. The failing catalyst was causing increased emissions and affecting engine performance. Multiple components required replacement including the manifold gaskets, heat shields, and the complete NOx catalyst assembly. This was indeed a serious issue requiring immediate attention, as a failing emissions system can lead to decreased fuel efficiency and potential engine damage if left unrepaired. The repair took two full days at the shop. Important note: The S5 and S4 share similar exhaust system architecture, so the repair process should be comparable. Would strongly recommend having a certified Audi specialist handle this repair due to the complexity of the emissions system components and the need for proper diagnostic equipment.

Thanks for sharing your experience. I am having the exact same symptoms with my Audi S5. Currently watching the NOx emissions values closely and they are way off. While the exhaust noise is annoying, I am more concerned about potential engine damage if I keep driving it like this. Did you remember roughly how much the total repair cost was? Also, has the fix held up well since then or have you experienced any other emissions system issues? I am planning to take it to a specialist this week since the nitrogen oxides readings keep getting worse. Just trying to get an idea of what to expect cost-wise before I commit to a specific shop.

I got it fixed last week actually. The automotive repair specialist found that the main issue was a significant leak in the exhaust system near the NOx storage catalyst. The good news is that after proper diagnosis, they determined the NOx catalyst itself only needed reconditioning rather than full replacement. The total repair came to 265 Euro for fixing the exhaust leak, which included labor and parts. This was much less than I initially feared, especially since I thought I might need a new catalytic converter. The NOx emissions values are now back to normal levels and the exhaust noise is completely gone. The fix appears solid, no check engine lights or unusual readings since the repair. The specialist explained that addressing the leak early prevented more extensive damage to the emissions control system. The NOx catalyst aging issue was resolved through their reconditioning process, which saved significant cost compared to replacement. Based on my recent experience, taking it to a specialist is definitely the right move, especially with those increasing nitrogen oxides readings. Early intervention likely saved me from more costly repairs down the line.

Finally went to get it fixed yesterday. Found a specialized shop after getting recommendations from fellow Audi owners. The mechanics immediately spotted multiple issues with the exhaust system during inspection. Main problem was indeed a damaged NOx catalyst and several deteriorated gaskets causing the leaks. Complete repair took about 6 hours. They replaced the NOx catalyst assembly, installed new gaskets, and performed a full emissions system diagnostic. Total cost came to 890 Euro including parts and labor. More than I hoped but less than I feared given the extent of work needed. The air quality sensor readings are now perfect and the annoying exhaust noise is completely gone. The automotive repair team did a thorough job explaining everything and provided a 2-year warranty on the work. No more check engine light and the engine feels much smoother during acceleration. Really glad I addressed this promptly instead of risking more serious damage. The failing catalyst could have caused bigger problems if left unchecked. Already noticed better fuel economy after just one day of driving with the properly functioning emissions system.