Catalyst advice please

Page may contain affiliate links. Please see terms for details.

andreas_t

Active Member
Joined
Oct 5, 2005
Messages
61
Location
Kenilworth
Car
GT C
Hello Folks,

The beginning of my saga has been documented elsewhere; here is the most relevant thread: http://www.mbclub.co.uk/forums/showthread.php?t=23822

Anyway, after several bits of correspondence with the dealer, they agreed to have the car in for extensive tests (eventually, they agreed to FOC ...). Within a couple of hours they came back and said that the catalyst is 'breaking up around the edges' and they recommended a replacement (part goodwill, but still £640 odd ...) before 'carrying out further tests'. :(

I declined saying that I wished to 'sleep on it' and asked them to change the air filter element as a precautionary measure. When I picked up the car more pressure was put on me to have it replaced, but I shrugged it off by saying that, at the moment, I have no real (other than the increased diesel consumption) motivation to spend that kind of money (and the car has just passed its MOT) - so NO THANKS. What I really wanted was to buy myself some time to do some homework ..... here goes then, my two questions (I eventually got to the point ....) are thus:

1. Does the story sound to you plausible - or are they just guessing at my (suggested) expense ?
2. If it looks like I need a new cat, does anyone know a good OEM or equivalent source ? - (car is E220CDI W210 2001 model)

:confused: I would be grateful if you can pass comment.

PS. And the best bit was !!!!! - They told me not to use Millers Diesel Plus additive as MB claims is damages the coating of the injectors and the fuel pump :eek: - and it might be the cause for my cat going south .... Hmmmm :rolleyes:
 
Might have just been my suspicious mind but when i bought the first MB i was sure the dealer was milking the signature warranty!

Regarding the CAT i purchased one recently along with the full exhaust for my C180 and fitted it myself, it came from Bosal / Exhaust Shack. Had a look for yours but either the server was down or i was picking the wrong one!
 
I have vague memories of reading somewhere about turbo oil seals failing prematurely on this model. This would certainly give smoke especially on the overrun on a warm engine.
 
Wully said:
Might have just been my suspicious mind but when i bought the first MB i was sure the dealer was milking the signature warranty!

Regarding the CAT i purchased one recently along with the full exhaust for my C180 and fitted it myself, it came from Bosal / Exhaust Shack. Had a look for yours but either the server was down or i was picking the wrong one!

Thanks Wully. I had a quick look at their website as well. It has the exhaust/catalyst, but I can get no price for it. I'll send them an email and see what they come up with price-wise.

Thanks !
 
grober said:
I have vague memories of reading somewhere about turbo oil seals failing prematurely on this model. This would certainly give smoke especially on the overrun on a warm engine.

Thanks Graeme/Grober - the blue smoke (referenced thread) proved to be a red herring - they were simply guessing (but failed to even apologise about it !) and it has been completely discounted now that I have done 2.5K miles and not a drop of oil added !

The real prolem in my head is - now that I know they are guessing - whether they are guessing about the catalyst as well !

Thanks for taking the time to respond anyway.
 
If the catalyst is rattling then it's breaking up, but if it is blocked then a pressure test upstream of the cat would tell all.
To perform the test you need to drill a hole into the exhaust downpipe and connect a pressure gauge. high pressure = blocked cat.

Cats on modern MB do seem to break up so it is possible.
 
Thanks Dieselman

As a follow-on:

Dieselman said:
If the catalyst is rattling then it's breaking up, but if it is blocked then a pressure test upstream of the cat would tell all.
To perform the test you need to drill a hole into the exhaust downpipe and connect a pressure gauge. high pressure = blocked cat..

What sort of damage might be caused if the CAT is blocked ? - The MB mechanic did not say 'blocked' he said 'breaking up around he edges'. Also, how can I tell if it's 'rattling' ? - I can't say I have heared anything 'rattly' at all.

Oh, and drilling holes I can't plug are definitely a no-no with me (never mind the lack of a pressure gauge)

My thoughts at the moment are to drive it for a bit and see if the situation improves - given that I got them to change the air filter and that in the last 400 miles the smoke seems to have reduced a bit. Maybe it gunged up a lot when the injectors were up the creek and it needs a bit of rigorous driving with the new air filter to burn it all up - nothing to lose I suppose.

Finally, do you know any good exhaust/catalyst sources (other than MB) and would I be wasting my money buying non-OEM ?
 
andreas_t said:
Also, how can I tell if it's 'rattling' ? - I can't say I have heared anything 'rattly' at all.

We had both cats replaced on the ML270 when it was about 15 months old. Now 15 months later, the symptoms are back, so it's booked in to the dealer for a quick diagnosis on Thursday.

Tell tale signs last time, and now this time are as follows - dealer did say these are classic symptoms:

(1) At the very early stages there is a very light tinny rattle at idle - often most noticeable when cold. May not be noticeable with windows closed.

(2) With a little time it will start to becom audible at light throttle. Again may not be noticeable with windows closed.

(3) Rattling sound becomes more substantial (less tinny), and coarser sounding. Becomes louder and noticeable at a variety of engine speeds and may tart to become audible with windows closed when accelerating hard.

(4) Very definite coarse rattle constantly - you really can't miss it!!

Dealer said should be OK to drive still, but to minimise use and be sympathetic. I have heard but not seen any documented evidence that aswell as being blown out through the exhaust, fragments from the catalyst can be sucked back in to the engine causing damage - not sure under which circumstances, but I'm guessing following sudden release of accelerator pedal when accelerating at full load?

In my case I could have put the first pair of cats down to a duff batch, but a second set (if that's what the diagnosis confirms) is more concerning. One would imagine that the cause lies elsewhere, and if un-fixed will haunt me again in another 15 months.

I would also be interested to hear about any aftermarket catalysts as the ML is out of warranty in September!!
 
Ive had a pair of cats on my SL changed at just 45k, another member on here Peterchurch (i think), had the cats replaced 3 times under a mb signature warranty. It is clearly an issue, and MB will have to face up to it sooner or later. Another sign of the decline in build quality.
 
Cant say as i've heard of a failing CAT making a car dish out blue smoke. Rule of thub is rings with blue smoke but that would mean oil consumption - which you dont appear to have !.

Unfortunatley even OEM CATS ( from say POWERFLOW) are about £250 a piece - i dont know about your car but my CLK has 2 :-( so there not cheap !

If your experiencing excessive fuel consumption and no oil loss - that must point to excess fuel being burnt and hence the blue smoke ? I no merc or diesel expert but have you checked all the fuel pipes ?

No smoke without fire - so id be carful - maybe your lucky its a diesel and the fuel wont ignit easily but that would be my concern ! Hope you get an answer soon - just thought id add 2p to the discussion .........

Regards

G
 
Bobby Dazzler said:
I have heard but not seen any documented evidence that aswell as being blown out through the exhaust, fragments from the catalyst can be sucked back in to the engine causing damage - not sure under which circumstances, but I'm guessing following sudden release of accelerator pedal when accelerating at full load?

This can happen on the close coupled cats. The exhaust pressure cant flow through the cat so flows around the sides and back towards the engine from behind the cat honeycomb. This can cause severe bore scoring if it happens.
 
andreas t, I own a E220 CDI and it is smoking in exactly the same manner as yours is. Sitting at a traffic light with the transmission in D is the most annoying situation. My car only has about 20000 miles however. Absolutely no oil consumption and the dealers here in Pakistan are totally nuts. I have an air mass on order since last weekend I had an utter loss of power which I felt is due to the MAF but as Dieselman suggests, I ought to take a look at the Turbo wastegate and EGR. While my car was making no power, there was no smoke!!!! So I am keeping my fingers crossed and hoping that the problem gets solved. I wonder what would removal of the Catalyst do? i.e. any change in the driveability? In Pakistan, we dont have to go for MOTs etc.
 
Removing the CAT will typically release between 10 and 20 bhp - However I dont think decat pipes are very common for mercs !

One option is to get an old CAT, Open it up, smash out all of the innards and weld shut - hey presto - a decat pipe :).

Still finding it hard to believe a CAT can case blue smoke though - It has to be burning either oil or fuel !
 
GarethM, I would reather have the CAT opened, emptied and weld shut. But, wouldn't this cause noise like an empty can???? Years ago, I had a Mazda 929 in which the CAT was blocked due to Leaded Gasoline. This caused it to blow blue smoke profusely grabbing our attention for it to be removed. I could not think of anything else besides the MAF which shall arrive in week or two that could cause mine and andreasT's cars to smoke since the oil level is the same???????????????????
 
Asif Kazani said:
andreas t, I own a E220 CDI and it is smoking in exactly the same manner as yours is. Sitting at a traffic light with the transmission in D is the most annoying situation. My car only has about 20000 miles however. Absolutely no oil consumption and the dealers here in Pakistan are totally nuts. I have an air mass on order since last weekend I had an utter loss of power which I felt is due to the MAF but as Dieselman suggests, I ought to take a look at the Turbo wastegate and EGR. While my car was making no power, there was no smoke!!!! So I am keeping my fingers crossed and hoping that the problem gets solved. I wonder what would removal of the Catalyst do? i.e. any change in the driveability? In Pakistan, we dont have to go for MOTs etc.

Asif,

It could be that by fixing one we can get both cars sorted. Yes, it is really embarrasing at traffic lights or when pulling away hard (I even have puffs of grey/brown smoke when I accelerate at motorway speeds). The MB garage has now run all the tests they could and pointed the finger at the catalyst - I am still not convinced.

I had them change the air filter and there is noticeably less smoke now - but still there. Certainly when I start it in the morning, there is very little smoke out the tail end (I used to get a smelly grey cloud). And fuel consumption has dropped slightly - it returned 41mpg on a 170 mile run yesterday between home and Reading (including 45 minutes stuck in traffic around Oxford :( ). Not as good as the 44-45mpg I would normally get for this journey, but not far off. Whether this is due to the new air filter or not, I do not know yet. It could be that when the injectors were going (and they were going for at least 2 months) a lot of gunge was accumulated in the catalyst / other part of the system and this is now gradually clearing up. Or it could be that when MB removed the catalyst to examine it, they put some compressed air down it (anything is possible).

I am waiting to hear how you get on with the MAF replacement. As I said previously, MB checked injectors, turbo, MAF, EGR, temperature and oxygen sensors and everything came spot-on. The car passed the MOT emissions test back in February when it was smoking hellishly, so problem is not yet severe if it is the catalyst (and gives me little motivation, other than the extra diesel burned, to fork out £750 for a new catalyst from MB).

Only difference to yours is that I don't have any loss of power - still goes about like a brick tied to a rocket. Removal of the catalyst is, unfortunately, not an option in the UK - I am sure my neighbours will be the first to grass me !

I'm looking forward to your next post ! - regards, Andreas.
 
Last edited:
GarethM said:
Removing the CAT will typically release between 10 and 20 bhp - However I dont think decat pipes are very common for mercs !

One option is to get an old CAT, Open it up, smash out all of the innards and weld shut - hey presto - a decat pipe :).

Still finding it hard to believe a CAT can case blue smoke though - It has to be burning either oil or fuel !

It's definitely burning fuel ! - No oil consumed and MB have now 'retracted' their 'burning oil diagnosis' :rolleyes:

Probably a colour-blind mechanic .....:devil:
 
Andreas,
I am seriously thinking of going through the CAT mod as I know that Diesel Fuel in Pakistan is amongst the worst in the world. Regarding my car loosing power, it just did so Friday morning and has been fine since then. The smoking is "exactly" the same as your car's though. The main reason why it is all mind boggling is that there is "No Oil Consumption"!!!!!! I have had the MAF ordered in Dubai, UAE and should take about a week to have it in my hands. We shall both keep in touch in case anything changes.

Regards,

Asif.
 
.........hmmm. Gets me thinking, would unburned fuel cause grey bluish smoke???
Any ideas anybody?????
 
Last edited:
Bobby Dazzler said:
We had both cats replaced on the ML270 when it was about 15 months old. Now 15 months later, the symptoms are back, so it's booked in to the dealer for a quick diagnosis on Thursday.

Wife took ML to dealer today and - phew - not the catalysts!!

Tech said they've now had a few cars in that have had new cats in recent past, and which hadn't been positioned and secured as well as they might have, and through time touch other components, giving a similar sound to a damaged cat. They adjusted and tightened and she's now sweet as a nut.

MB Walsall - have a nana :bannana:
 
Asif Kazani said:
.........hmmm. Gets me thinking, would unburned fuel cause grey bluish smoke???
Any ideas anybody?????

Can do. It's known as Quenched combustion.
 

Users who are viewing this thread

Back
Top Bottom