Hi folks,
The CAT on my 1994 220 petrol C class with approx. 100000 miles on the clock, has started rattling when cold on tick over and is noisy at high revs so it appears that the ceramic core is breaking up. While enquiring about the price of a replacement, the exhaust retailer implied that they had sold a number of this model recently and that I should have the car checked for over fuelling as this is the reason for the existing CAT failing and that a new one would not last long unless the fuel problem was fixed first. All sounds reasonable from what I then read on the web. However I have also been told that for the car to be over fuelled enough to cause the CAT to fail the car would not be running perfectly well as it does.

So my question is what are the experiences of people who own these, would I notice the car running rough if it was over fuelling enough to fail the CAT?, is there a common fault known on this model? Or have people found there CATs failing around this age on this model?, or found other causes? Although the heat shielding around the CAT is in fairly poor condition it does not appear to have been hit which is the only other reason I have herd of for failures.

As a side question purely for interest the design of CAT on this model looks like 2 tubes welded side by side with the exhaust split between them, has any one cut one up? Is it just two small round cores in there or is there more to it?

Thanks in advance for any knowledge / experiences.

Marc