VW Fox Diesel Emissions System Failure and Repairs

I had a very similar issue with my 2011 VW Polo diesel last year. Having some experience with basic car maintenance, I first noticed the problem when the check engine light came on and there was a noticeable exhaust smell. The car diagnostics revealed it was indeed a leak in the exhaust system, specifically where the NOx catalyst connects to the main pipe. The workshop found several deteriorated gaskets and a crack in the connection point, which was causing the exhaust gases to escape. The total repair came to 265€, which included replacing the gaskets, welding the cracked section, and running a full exhaust system inspection. The fuel efficiency improved noticeably after the fix, and the check engine light hasn't returned since. Before suggesting specific solutions, could you provide: Current mileage on your Fox, Any unusual sounds from the exhaust area, Whether you notice the smell more at idle or while driving, If you have had any previous exhaust system repairs This information would help determine if your issue matches what I experienced. These symptoms often point to various potential problems in the exhaust system, ranging from simple gasket failures to more complex catalyst issues.

Just returned from my last service 2 weeks ago, mileage showing 12158km. The smell is definitely stronger when idling, and theres a slight rattling noise from under the car. The mechanic noted during service that the exhaust system was showing age-related wear but wasnt critical yet. No previous exhaust repairs on my records. Im wondering if maybe this has now progressed into a more serious issue impacting nitrogen oxides emissions control.

Thanks for those details. The symptoms youre describing match almost exactly what I experienced with my Polo before the repair. That rattling noise combined with the stronger smell at idle strongly suggests a connection issue between components, rather than a completely failed NOx catalyst. Based on your relatively low mileage and recent service notes, its likely youre dealing with gasket failure and mounting bracket wear, similar to my case. The good news is that the NOx catalyst itself might not need replacement, which would save significant repair costs. The automotive repair in my case focused on the connection points and gaskets, which resolved both the rattling and emissions issues. The check engine light in these VW diesels is particularly sensitive to any exhaust system irregularities that affect NOx emissions. My catalytic converter remained functional; the issue was purely in how it was connected to the rest of the system. Since youve already had a recent service, I suggest getting a second opinion specifically focused on the exhaust system connections. The repair costs should be similar to what I paid (around 265€) if its the same issue. Continuing to drive with these symptoms could lead to increased fuel consumption and potentially more serious exhaust system damage.

Based on your detailed input about the gasket failure possibility, I feel more confident about the repair direction. Those symptoms with the stronger idle smell and rattling definitely align with what you experienced. The repair cost of around 265€ sounds much more manageable than what I feared for a full NOx catalyst replacement. Since my mileage is relatively low at 12158km and the recent service noted only age-related wear, Im leaning towards getting those connection points and gaskets checked first. It makes sense that the emissions system warning could be triggered by faulty connections rather than a completely failed catalyst. Ill schedule a focused exhaust system inspection this week. The fuel efficiency impact you mentioned is concerning, so better to address it quickly before it leads to more extensive automotive repair needs. Thanks for helping narrow down the likely cause, its good to know the fix might be straightforward rather than requiring major emissions system components replacement.