[MattR99]

I've owned my lovely 2014 S5 Sportback Black Edition for a year now. I bought it with 1 previous owner, full Audi SH and lots of receipts showing no expense had been spared keeping it in tip top condition over the years. It's just turned 70k miles,
Over the last few months I've noticed a rattle under the car at low revs, usually with foot off the accelerator at low speeds in 1st gear. It sounded to me like a heatshield that was loose. I've just had it serviced and MOT'd, and was told it's the intermediate catalytic converters rattling. It sailed through the MOT, including emissions.
Is the cats going at this age/mileage common? Is it important to get them replaced sooner rather than later? Not a cheap job I think, they look to be £500 each side for after market ones - imagine Audi ones are a lot more

 

[Smokey Joe]

It will be the downpipes that are rattling not the cats. The downpipes have small resonators at the bottom often mistaken as cats. These are quite common to fail at that sort of mileage.

 

[MattR99]

Thanks @Smokey Joe , hoping thats potentially a cheaper fix. Any idea on whether it's something that should be fixed ASAP or one that I can live with for a bit?
Any way to be certain it's those rather than cats? Presume the garage just listened to it from underneath with it up on the ramp

 

[Smokey Joe]

I know a guy whos rattled for over a year before he replaced them so I don't think it's mega urgent, it's usually the flexi at the top of the downpipes that starts to fail causing the pipes to vibrate.

 

[MattR99]

One to monitor then, see if it gets worse. Thanks!

 

[Dave Kwatro]

The S5 doesn't have any intermediated cats. As Joe says, they are little silencers near the front underneath and often mistaken as cats. The cats on these are tucked up right beside the engine.

The rattle comes from the chain mail that covers the flexi joint at the top of the downpipes. They are nothing major and can be left.

I fixed mine with exhaust wrap and jubilee clamps. But now I have other aftermarket downpipes which have a mesh over the flexi joint, so it doesn't rattle like the chain mail OE flexi joints.

They tend to rattle just over 1000rpm, about 1200 on the way up and down revs!

 

[MattR99]

Hi @Dave Kwatro , thanks for your reply. It certainly sounds like that's what I'm hearing. It gives me more peace of mind that there's not a big bill around the corner! I'll stop worrying then and just keep listening out to check for it getting any worse.

 

[Dippy]

I'm surprised that I haven't read about this before - I thought I knew about all the known issues for this platform.