RGW

My 2003 A6 4.2 is still running great. It is an office only ride at the moment because the family vehicles get most of the mileage these days.

Recently, I started to hear a rattle from under the back of the vehicle.

I had it in for a wheel alignment and at that time, the shop said the rear catalytic converter(s) were making the noise.

They suggested replacing them with some aftermarket ones.

I wonder if anyone else has had this issue on a C5 4.2? I have nothing against aftermarket parts but previous experience has shown the quality is never up to OE.

I'm curious if there is any service out there that rebuilds these cats rather than replace them? That way, I could source a used set and have them rebuild, tested and installed back.

I'm open to suggestions. The car is doing great otherwise. It only has 77K at the moment.

Harleyguy

If the noise is coming from inside the cats then it indicates a baffle or other part of the internal structure has detached. Personally I would look at some of the aftermarket vendors for replacement. When catalytic convertors go bad they are normally recycled solely for recovering the platinum inside them as that is the active element that makes them work. Also the reason for the high cost. With such low mileage it would be well worth the cost of new cats.

tester123

See if you can locate the noise yourself. Don't trust the "mechanic". Cats going bad at 77k? something is off.