CLK (W208) catalytic converter problem

[JDMariner]

Hi

My year 2000 CLK 230 (W208) had a replacement catalytic converter at end of Jan this year (we just had the converter replaced, nothing else at the time). It's now already gone wrong again (rattling inside, broken ceramics I guess, same as original one). To get a replacement cat under warranty the company I bought it from are asking for a Forgas analysis (using the diagnostics setting on the emissions machine at mot test centre?). I'm guessing this is because they feel it's something else causing the cat to fail (which I fear is highly likely).

What should I check to see what is probable cause of problem? Searching the forums seems likely to be Lambda sensor, how easy to check/replace this?

Any help much appreciated! Thanks

 

[FazMan]

Often cats fail due to being driven through flood water.
The cats operate at a high temperature and the sudden shock of being immersed in water causes the core to break up.

 

[bouncer]

The four gas analysis is the way to go, this will point them in the right direction as to what’s happening with the engine management, as a cat will NOT increase the emissions. If it’s been over fuelling / running rich this can burn away the support cushions then the brick will rattle.

 

[x332race]

Did you change the Oxygen sensors? See this

 

[JDMariner]

Will know more later, the four gas analysis is being done today. Interestingly had a test done last week (didn't realise it was just an mot test rather than asking for the four gas analysis). That test showed the Lambda (O2) sensor as being fine so hopefully not that (and haven't changed them just yet as a result). Maybe it could have been caused by when having to drive through the bad snow a month or so ago??

Does anyone know what warning signs I'm looking out for on the four gas analysis when I get the results - what would/wouldn't point at engine cause rather than just the cat was faulty and the cars fine?

 

[JDMariner]

Argghh, hitting more problems. It turns out that where my car was taken couldn't do a four gas analysis as didn't have the right machine? I had been lead to believe that any mot test centre could do the analysis just by switching to a diagnostic setting on the machine used for the mot, is that not correct? Apparently the suggestion today was it could only be done at a Mercedes dealership??

Any help anyone, where can I get a four gas analysis diagnostic test done?? Help!!

 

[bouncer]

Will know more later, the four gas analysis is being done today. Interestingly had a test done last week (didn't realise it was just an mot test rather than asking for the four gas analysis). That test showed the Lambda (O2) sensor as being fine so hopefully not that (and haven't changed them just yet as a result). Maybe it could have been caused by when having to drive through the bad snow a month or so ago??

Does anyone know what warning signs I'm looking out for on the four gas analysis when I get the results - what would/wouldn't point at engine cause rather than just the cat was faulty and the cars fine?

Lambda reading on the emissions test will not tell you the condition of the lambda sensors. Lambda is the air/fuel ratio in the exhaust gas measured at the tail pipe.
If you need to know the condition of the lambda sensors then go and see a diagnostic specialist who can capture live data, the voltage and duration will be critical. Once you have your four gas data post it here and i will help if i can.

sTeVe

 

[bennesspipers]

Suggest you ring Prestige Car Service, nr Portsmouth,the owner (Olly) is a member on here, & comes very well recommended on here.

 

[JDMariner]

Hi everyone,

Unfortunately I've got to raise this one again as my blinking cat has gone AGAIN! Following the probs I had above we replaced the lambda sensor and plugs back in June time having had the car on diagnostics.

3 months later and it's gone again. The cats I've put on are BM Catalysts ones so sure it's not dodgy cats, obviously still something on my car causing the issue.

We had it put on a Star machine last week (car hasn't got OBD) and report showed that the MAF was at it's limits, so looking now to get a new one of those put on (Bosch 0 280 217 114), and then yet another cat to hopefully get my car working well again.

Quite simply, have any of you got any other suggestions?? As you can imagine I really just want to get this sorted once and for all - it's turned into an expensive year. Confusing bit is that my car doesn't run like an old dog normally and in fact was great until these probs since start of year.

Help! thanks

 

[BlackC55]

Get a genuine CAT on there. The after market type are often crap

 

[JDMariner]

I appreciate that after market cat may not be as good, but for them to fail so quickly as in my case, does that not indicate that there is still something wrong with my car causing excessive fuel to get to the cat in the first place?

Basically I don't want to stick a genuine CAT on there just to find that it get's shot to pieces in a few months too?

 

[tjs_riley]

I've been having similar problem on my 01 CLK 230K. Changed out a cat to an original mercedes one (welded on). What happened after was the resonator (which is located after the cat and before the muffler) then stuffed up because of the increased airflow through the new cat. Changed out a bunch of stuff because non of the mechanics could diagnose it. ( I was getting something like 14-15 L / 100 km fuel consumption so changed out the MAF, Oil Separator, cleaned out the Intake Manifold, re-did the Air Intake Piping, supercharger piping - all to no avail , if anything the fuel consumption became worse)

Finally the stuffed resonator was identified, cut out and replaced. Fuel consumption became better to 11L/100km. A tell tale sign that the resonator has gone is when you can feel increased heat from under the car, the stuffed resonator heats up way beyond normal, exhaust air flow is decreased, so probably the heat build up retroactively goes back to the cats, etc . Which MIGHT cause the early failure. Non of which would be picked up by computer diagnostics.

Just something to think about.