Catalytic Convertors on SL 320

[DD]

SL 320 (2000 X) - I am now on my third set of catalytic convertors in 24000 miles. Mercedes can't tell me why this has been necessary - has anyone else had this problem?

 

[Arnie]

Had mine changed at 6,000 miles as they were making a resonant clanking sound particularly from cold. Actually, they were like that since I got the one-year-old SL with 4,000 miles and the car had apparently passed the MB signature used car warranty!

At first I was shocked that a V6 should sound so rattly, but now with the new cats it sounds absolutely wonderful.

Apparently its a common problem on the 320 V6 engines, not only on the SL.

The catalytic core beomes loose inside the can and sounds as if you have a bag of loose nuts and bolts ratling around in there.

Part of the problem is that on newer engines the cats are situated much closer to the exhaust manifold so that they heat up much quicker and start working quicker to reduce emmissions. But this gives them much more thermal stress to go through and so it's not surprising that the core may come loose inside.

The worst is that you may get engine damage from ceramic (or sintered) particles from the broken core being sucked back into the engine (the exhaust is a naturally resonant system with pulsating gas flow). It is therefore important to change a faulty cat then as soon as its discovered, especially as the new ones are that much closer to the engine.

I also think that MB has had a bad batch of cats and must be sorting the problem with the suppliers.

 

[Tony]

Mine went at 12k miles (2001 SLK320). They said it was a bad batch and that I now have another 3 year guarantee. I hope so, as they're a vast amount of money. They also kept me waiting about a month to replace it. There was no mention of possible engine damage.

 

[clk200]

The CAT on my SL280 has just started doing this, the car has always been looked after and although its a 1998 car its only done 46K, with full MB history, you think id have any chance with a goodwill claim? Or would I be wasting my time?
Cheers

 

[Arnie]

Well, you can but try.... Maybe you can print out these postings as evidence. You may get part-costs, if not full.

 

[peterchurch]

Hi,
could these cars be run without a Cat? Precat failure was very common on my MR2 and the general feeling amongst owners was they got removed before they failed and took your engine with them ...

Regards

Peter

 

[190]

Pre 1993 cars did not need a cat but post 1993 cars do need a cat for the emission Levels in the Mot, I would say if Mercedes say a certain year of mercedes were fitted with faulty cats they should have a recall on the models affected before they break-up inside and cause engine damage by restricting the exhaust gasses.

 

[peterchurch]

The question was, will a new SL engine run without damage if you simply gut the CATs ? Now I think the answer is yes, and as for the MOT you could simply fit a standard exhaust for the point of the MOT test and remove it afterwards for another year of happy cat free motoring. If they keep going bang every 2 -3 years then why have them? find another way round the gases problem...

 

[Arnie]

The emmission levels are tighter for newer cars, such that if you removed the CAT or even just the material inside it (post 1993 cars must have one fitted), you may not pass the MOT for your age of car. But, you can try....

Anyway, one would hope that MB would sort this problem as the V6 range of engines is still current and fitted to many cars.

 

[clk200]

Just a quick update, I took it to a dealership and they submitted a claim, which got quickly declined. Mainly due to the age of the car. The service manager said himself that the 112 engines in the 280's and 320's are prone to cat failure. This is not caused by the engine runing incorrectly, but just the fact that the cats fail. Well im going to find a non-mercedes part, considering the number of MB CATS 'DD' has had fail.
Thanks for your help.

 

[peterchurch]

If you have not already bought some this might be of help

http://www.bba-reman.com/cats.htm