Has anyone had a cat fail on w220 s500?

[harry kular]

Hi,
our 2003 s500 has a rattle at idle that we traced to the cat. Does this mean it's done and must be replaced, or is a repair possible? Its a well cared for car, we've had it since new and its only done 25k!

Any thoughts/ advice would be appreciated!

[r129sl]

Ignore it?

Lots of horror stories about cat disintegrating and being ingested back into the engine (can't see that happening somehow).

Mine used to rattle and did so for 100,000miles or more. It's fairly inevitable if you live in the sticks. The most common cause is driving through flood water with hot cats, the temperature shock does for them.

[harry kular]

Ignoring it isn't an option- my grandfather is very particular about everything in life, and won't let it lie. He cleans it every sunday regardless if he drives it or not, serviced on the button by MB etc... It MUST be perfect.
Maybe I'll fit a decat pipe to unleash the v8 burble a bit more, but I doubt he'd let me!

[sanguinary]

Silly question time. Are you sure it's the cat?

I only ask because I had a simlilar problem on our SLK. I was convinced the cat had a rattle at idle by both looking at it and feeling it (before it got too hot!), to a point that I figured it would fail it's mot on emmisions.

It turned out to be a bracket just above the cat, which had broken loose. A little bit of welding and it was tip top again.

[AC43]

I had rattles coming from my E500 exhaust. Turned out to be 2 x broken mounting brackets and a broken cross brace. Had them welded back up for £50.

Heatshields can also cause rattles.

[jke11y]

I too had ratlling cats on my 2000 r129 - ended up getting them replaced at TopGear in St. Albans for about £250 for the pair. Didnt want to chance not getting an MOT with replacement pipes. The replacements have been on for 10k ish now.