Hello - do you have experience of Cat failures at low mileage?
My 2004 coupe has done 22,000 miles and has 3 mths warranty left. UK Dealer says both cats need replaced (under warranty) and that they recently had the same issue on another Crossfire.

I do use the Crossfire as often as possible because it's such good fun, but maybe I should use the other car for short journeys around town if this is an issue. Could there be another cause of the failure rather than just short journeys - maybe have the dealer check out the sensors?

Cheers,
Lowlander

 

I has been known on other 320 engined MB cars in the past but I don't think it is common. There are actually 4 cats, which ones have 'gone' and how have they determined that? Has it failed an MOT or has the MIL just lit up and thrown a code based on the rear O2 sensors detecting a loss of cat efficiency? I'm curious because mine is of similar vintage. At least it is still under warranty.

 

Woody, don't count on the CEL / MIL as an indication ... This is one of the many things I forgot to share with you... After removing my cats quite a few months ago and having the "custom" exhaust built, we added a longer bung (+ 5mm) to the aft 02 sensor holes to re-insert the secondary sensors in the approximate same position... I expected the CEL to illuminate from the removal of the cats, but it never did... And still has not... And it has not thrown any DTC's...

 

As a side bar, I've been scratching my head about this one... It seems like a whacky idea but it comes from a MB mechanic that races with our group...

With regards to the fueling / timing retard that the ECU forces stoichiometric AFR of 14.7:1 on this car no matter what... It was recommended, as a "cheap" timing / fueling "trick" to allow a small bit of air into the forward 02 sensors which will trick the ECU into richening the mixture and advancing the timing...

Since we know that the front 02 sensors are directly responsible for the ECU timing / fueling adjustments, what's your opinion ? It seems like a crazy idea, but it also sounds logical...

It was suggested that I install a small bung, (1mm) with a tiny tube adjacent (upstream) of the L&R sensors in bank 1 that will create a small vacuum of air from the tube caused by the exhaust gasses and be blown directly onto the sensors... This will in-turn "trick" the ECU into richening the mixture and advancing the timing...

I think it's a crazy idea but I saw this little thing installed on a TurnerMotorSports race BMW...

 

Hi - thanks for the swift replies.

My Crossfire is just under 3 yrs old, so hasn't had an MoT test yet - so I'm unaware of what the emission readings are. There are no warning lights/indicators of any kind, in fact not even the "service required" icons have appeared (although just 10k from last service).

The two Cats in the middle of the car have gone, located in the centre of the car, under the transmission tunnel. I was hearing a rattle and had thought it was the rear end as I previously had my dealer fix those rattles.

I thought I'd get my local tyre and exhaust centre to check it out before I went back to the dealer. They said the inside of the cat had melted and was now rattling around inside the shell - they though it likely it was caused by a faulty sensor.

A few days later I has the dealer check it out- they confirmed the cats were gone and would be replaced under warranty - this will be carried out on Thursday. Should I be looking for the dealer/Chrysler to establish a root cause, rather than wait for another expensive repair when out of warranty? What I mean is - is Chrysler/dealer obliged to investigate the root cause of the failure so ensure it doesn't happen again - or are they simply entitled to replace the failed part and leave it at that?

 

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Hi AMGlover,

Car seems to be running fine - mixture is neither rich or lean as far as I know - but I can ask the dealer to check it out to see if this a factor.

Tyre and Exhaust centre guys know me and that the Crossfire was under warranty - so there was no chance of me buying a new exhaust /cat from them.
They simply reckoned the cats were melted and to take it to a dealer for replacement. Dealer confirmed what had been said earlier.

I do accept your point that the front cats might be damaged too...

Regards,
Lowlander

 

I have a 2004 Roadster which I purchased new in 2006, and a few months ago I had a rattle appear, took it to the dealer, and they found a Cat Converter had failed, and was rattling inside. They apparently had to replace 3 of the 4, something to do with the fact they were laser welded. (I didn't really care so long as it was fixed under warranty).

I was led to believe by the service manager, that it was a quality issue with the converter itself. My car had done about 15,000 kms when the converter went. The service manager told me that if I had to pay for the job, it would be around AUD $2,500, which converts to 1,050 pounds, or US $2,134., not cheap in anyone's money!!

 

Yes, the joints in the downpipe sections are arranged such that one pipe has 3 of the four cats and the other only has the one, even though they are mounted symmetrically either side.

 

Hi,

Cats now been replaced and car running well. Like post above, Service Manager suggested the failure was due to poor build quality of the Cat itself as opposed to any other fault elsewhere being the root cause of the failure.

Thanks to all for the replies.

Regards,
Lowlander