Help please, suspected cat failure (CLK)

[LeighW]

Hi everyone, I've just joined the forum, hope someone can help me. I have a 2000 CLK320 Avantgarde which has developed a fault. Yesterday when I started it from cold, it seemed to be running slightly rough, when I pulled away it was really lethargic, and the check engine light flashed, then stayed on. The rough running went away, but the performance was flat (I'm guessing it has some sort of limp home mode?). Anyhow, the light still illuminated when I drove to work this morning, but after I stopped at a shop on the way to work, the light went out when I restarted the engine. I rang my local MB dealer (Loughborough Mercedes) and arranged for them to plug it into their diagnostics. The report shows it has misfired on all 3 cylinders on the left bank (as you look at the front of the car). The technician (very helpful chap) thinks this all points to one of the cats (probably the rear - I didn't realise it has 4!) breaking up and blocking the exhaust. He wants me to leave the car with them, they'll remove the suspected faulty cat and tip water through it to see if it's flowing ok. Apparently I'm looking at over £800+vat for the part alone, plus labour of at least 2 hours at £95+vat per hour. Ouch.

Does anyone know of a cheaper source for the parts (if it turns out the cat has failed), a decent specialist in my area - North West Leicestershire, or alternatively, would a much cheaper fix of replacing the rear pair of cats with straight pipes have an adverse affect on performance? Would the car pass it's MOT on emissions with just the front cats?

Any help at all would be gratefully received.

Leigh

 

[Birdman]

If the price you quote is to replace the entire catalyser system on both sides that would be about right. If it's just one side it is far too high imo.
There have been a number of threads on fitting non-MB parts and there are pros and cons. Some members have fitted non-MB parts and stated they would never make that mistake again. Others seem happy with the price saving they obtained going to non-MB suppliers. It does depend on your source of supply it seems.

Enter 'catalyst' in the search menu on the toolbar and check out the threads, such as: http://mbclub.co.uk/forums/showthread.php?t=7041&highlight=catalyst

For local independents check out the pages at:http://mbclub.co.uk/forums/forumdisplay.php?f=13

Here's one lead:
http://mbclub.co.uk/forums/showthread.php?t=11073&highlight=Leicester

Doubt anyone could know the effect of removingthe front cats (except to make the car ilegal!) but on a year 2000 car it's not an option imo.

Good Luck!

 

[LeighW]

Thanks Birdman,
It's going in for it's MOT tomorrow (convenient time to need an MOT - not!), we'll see how it gets on with emissions. Regarding the cat removal, I was just wondering if the car would still pass emissions regs with just the front pair of cats (ie, if you got rid of the rear pair).

 

[stats007]

Hi,

I might be wrong but doesn't the cat system just come in two parts for the CLK320? The more expensive part carries the rear section as well as the right hand side cat? The left cat is seperate.

A2084902219 £780

A2084902319 £370

Shude?


Like this?

 

[Birdman]

Cats normally last 100K+ miles if not stressed by Eexternal knocks or incorrect fuelling. A replacement system on my E55AMG is about £400-£500+VAT per side just for the cats themselves (so I'm told) depending where you source them from

I see where you're coming from re dumping the faulty cat. One of the threads I've seen recently contains a 'Howto' on cutting open the cannister, extracting the matrix inside and resealing it to look like new. It involves cutting and welding a section of the cannister so is an amateur workshop job, but probably not something even an independent garage would likely contemplate.

I guess you'll post the results of the MoT?

 

[Birdman]

This thread describes two different ways of tackling cat removal.

http://mbclub.co.uk/forums/showthread.php?t=28126&highlight=cat+welding

Now if you swap out the petrol engine for a 320CDi diesel it seems you would pass the emissions test, according to our resident expert!

 

[LeighW]

Hi,

I might be wrong but doesn't the cat system just come in two parts for the CLK320? The more expensive part carries the rear section as well as the right hand side cat? The left cat is seperate.

A2084902219 £780

A2084902319 £370

Shude?


Like this?

Thanks for that, yep, that's exactly how the exhaust looks. I didn't realise that part had 3 of the cats in it, it would go some way to explaining the cost though. Funnily enough, I had a Mitsubishi Evo 7 prior to this, and was sick of the horrendous running costs (try services every 6 months or 4500 miles), so I thought I'd get myself a nice reliable german car...

 

[LeighW]

This thread describes two different ways of tackling cat removal.

http://mbclub.co.uk/forums/showthread.php?t=28126&highlight=cat+welding

Now if you swap out the petrol engine for a 320CDi diesel it seems you would pass the emissions test, according to our resident expert!

If I thought I'd get away with the emissions, I'd do that. I have friends that could tackle the exhaust 'modification'.

My uncle has a E320cdi, I wonder if he'd notice if I swapped engines...

I'll post up my MOT results, if it passes, I may gut the offending cat, it at least gives me time to source a cheaper (maybe 2nd hand) replacement.

Thanks again for the replies chaps, much appreciated.

 

[rajinder_1]

Leigh,
I dont think it is your cats to be honest!!!!!! if it were the cats then you would have the problem all the time not on and off...

If it is your cats then trust me and ONLY BUY GENUINE MB.... i have had a nightmare with my aftermarket ones and am in the process of getting them replaced.
I thought the same as you get them cheaper. for the headache i would have rather paid the extra and bought genuine.
Try these before you change your cats:
MAF sensor ( get it checked )
Fuel and Fuel Filter
Plugs
Coils
Leads

not in any order but i would try them as like you say cats will cost you in excess of £700

Raj

 

[LeighW]

Leigh,
I dont think it is your cats to be honest!!!!!! if it were the cats then you would have the problem all the time not on and off...

If it is your cats then trust me and ONLY BUY GENUINE MB.... i have had a nightmare with my aftermarket ones and am in the process of getting them replaced.
I thought the same as you get them cheaper. for the headache i would have rather paid the extra and bought genuine.
Try these before you change your cats:
MAF sensor ( get it checked )
Fuel and Fuel Filter
Plugs
Coils
Leads

not in any order but i would try them as like you say cats will cost you in excess of £700

Raj

Thanks for the reply Raj. I have to say, when the light first came on, I thought it was the MAF, - I'd done a bit of reading on here, but the fact that it's all 3 cylinders on one bank logging a misfire suggests otherwise. The tehnician said that that it was pointing to the cats as it's the only thing that all three cylinders share. If it was a plug, a lead, or a coil pack, surely it would be just one failing, causing a misfire on just one cylinder? It certainly isn't misfiring at the moment, although it does feel a bit flat on performance. I'm just taking my time driving it at the moment, don't want to cause major damage. If the MAF was not working as it should, would it it not log it's own fault?

I'll scan the diagnostic sheet in, and attach it, see what people think.

 

[LeighW]

Here it is:

 

[Birdman]

If just one cylinder bank is involved in the fault - on the offside of the car - the exploded diagram shows two cannisters lying on the single pipe which connects to the offside (faulty) bank, not three, as LeighW suggests. And I guess that makes it clear why replacing a faulty cat on that branch it is roughly twice the price of replacing a single faulty cat among the two sitting on the other branch. The diagram does show the engine has two cats on each branch, not three and one, which is where my puzzlement started.

The large central cannister is presumably an expansion box to muffle the engine exhaust and assist gas flow.

Not being much good at reading mechanical diagrams I'm pleased to have worked this one out, finally, - thank you stats007.

Further corrections to my tenuous grasp of these things are always welcome!

But maybe the garage will come up with an altogether new explanation - once the cat has been changed!!

 

[LeighW]

If just one cylinder bank is involved in the fault - on the offside of the car - the exploded diagram shows two cannisters lying on the single pipe which connects to the offside (faulty) bank, not three, as LeighW suggests. And I guess that makes it clear why replacing a faulty cat on that branch it is roughly twice the price of replacing a single faulty cat among the two sitting on the other branch. The diagram does show the engine has two cats on each branch, not three and one, which is where my puzzlement started.

Obviously each bank has two cats, but if you look, the two offside cats, the 'Y' section where two pipes become one, and the rear nearside cat is all one piece. That's what I was getting at.

 

[LeighW]

Ok, this is strange, albeit good news. The car passed it's MOT, and as you can see from the scanned results, it absolutely sailed through the emissions test. I told the tester (small local garage) about the situation, he thinks my cats are fine, and says if it was badly enough broken to block the exhaust, it would be rattling, which I can't say I've heard it do. The exhaust seems a little 'raspy' if you blip the the throttle when cold, but that's about it.

The car seems to be driving ok, although I am taking it easy, and the light has stayed off, so I'm at a loss. Any suggestions what to do now?

 

[Birdman]

Obviously each bank has two cats, but if you look, the two offside cats, the 'Y' section where two pipes become one, and the rear nearside cat is all one piece. That's what I was getting at.

You're absolutely right. What a strange thing for MB to do
Perhaps have a word with your garage and wait for the fault to re-appear?
It could be to do with the fuelling rather than any blockage.
Btw what is the current mileage?

 

[big x]

Have you noticed an increase in fuel consumption ?
If the camshaft sensor is faulty the warning light will come on
and the ECM will default to simultaneous fuel injection instead of
sequential leading to higher fuel consumption as the timing is not
accurate.The coolent temp sensor also needs to be checked.If it's stuck at
one output no fault will be logged but the ECM may be over fueling what it reads as a cold engine.
Fault code P2085 seems to be listed in your readout so what makes MB mention the cat?
It's the cat that gets damaged by overfueling.

adam

 

[Glenn Smith]

I would say it's a plug lead/coil fault, i had asimilar fault on my jag, this has similar 4 cat system and one cylinder misfire will cause poor running on 3 cylinders due to the lamda sensor on that bank detecting a rich mixture and attempting to adjust.

 

[LeighW]

You're absolutely right. What a strange thing for MB to do
Perhaps have a word with your garage and wait for the fault to re-appear?
It could be to do with the fuelling rather than any blockage.
Btw what is the current mileage?

I know one of the mechanics who works at my MB dealer, although he's on holiday at the moment, maybe he could offer a different opinion to the mechanic I saw. I really don't think it's the cat, I blipped the throttle when the engine was cold this morning, there's no rattling whatsoever.

The mileage is 74k at present.

 

[LeighW]

Have you noticed an increase in fuel consumption ?
If the camshaft sensor is faulty the warning light will come on
and the ECM will default to simultaneous fuel injection instead of
sequential leading to higher fuel consumption as the timing is not
accurate.The coolent temp sensor also needs to be checked.If it's stuck at
one output no fault will be logged but the ECM may be over fueling what it reads as a cold engine.
Fault code P2085 seems to be listed in your readout so what makes MB mention the cat?
It's the cat that gets damaged by overfueling.

adam

Thanks for the reply Adam. The reason that the mechanic suspected the cat being at fault was purely that all three cylinders on one bank had misfired, and the cat was the one thing that they all shared.

What is code P2085?

I'm getting approx 22 - 23mpg on my daily 6 mile commute, pretty much the same as normal. It isn't misfiring now, but I'm sure it's down on power, especially at lower revs, at small throttle openings, and particularly when the engine is cold. It seems fairly ok when it's up to temperature, although throttle response doesn't seem so sharp as it was. It sounds fine though, perfectly smooth. The gearchange isn't great, which also points to poor running I guess.

 

[LeighW]

I would say it's a plug lead/coil fault, i had asimilar fault on my jag, this has similar 4 cat system and one cylinder misfire will cause poor running on 3 cylinders due to the lamda sensor on that bank detecting a rich mixture and attempting to adjust.

Does my car have a seperate lambda sensor for each bank? Makes sense if so.