Choked Exhaust on a E220 CDI

[Asif Kazani]

O.K. Guys, listen up. I need all the ideas that you could help me with. As part of my ongoing quest to sort out my car's smoking problem, I had the CAT removed today and a pipe of the same diameter welded in it's place. When we pressed the accelerator to check for any leaks, it seemed like the exhaust was all choked up and the spring linkage/flange up front literally expanded to let the gas out. We then removed the whole exhaust and tried to check for choking with an air hose. Guess what, it started blowing out near the air hose area which we were trying to cover with a piece of wet cloth. I mean, I know that there is supposed to be back pressure but this just is not right. It seems like the boxes are choked with oily residue which was there in the tail pipe too. This was probably the reason why my Turbo gave up so soon. I am having the rear muffler and the small box in the middle opened from the top, cleaned out and welded back up since the system is not readily available here. Any ideas?????? Have you all seen an exhaust so choked up??? All the Mercs that I have had up till now have been direct flow and I don't know what is causing it to choke???

Asif.

Edit: Sorry, car is a 2000 E220 CDI

 

[jimmy]

Not seen it on a Merc but I have a Ford Mondeo 2.5 V6 in the workshop at the moment, it has 3 silencers on it, one of them has ruptured and all the wadding has come out and blocked the system somewhere as no gas is coming out of the back. Like your Merc the spring flange is opening allowing the engine to breathe.

Fitting a whole new sytem including CAT next week, not too bad as it only costs £150 but would be more on the Merc.

 

[silverarrow]

i think you will find possible injector leak and blow pass is occuring and the residue is building up in the exhaust system hence why turbo duff have a look at the engine underneath the rocker cover any sign of a leak or tar ???
good luck
may need whole exhaust and manifold to come off ???

 

[Asif Kazani]

No such sign anywhere silverarrow. The whole saga may be due to the high sulphur diesel here or the constant low speed and traffic we have to drive in here.

Had the system reinstalled today after a thorough clean up. Yesterday, after removing the bottle shaped canister aft of the Turbo, I was thinking that I had done away with the CAT but the center small box had the same fine mesh block as the canister upfront. This was probably the second CAT and the mesh was so blocked on the inlet side that it seemed like it had been cemented with soot. Had the ceramic mesh block removed, the box welded up and the system reinstalled and voila! Loads of torque and better throat!! I was thinking that the sound of the exhaust would be loud but the only thing I hear is the lovely Turbo song and the throat of air intake is definately louder, showing that it is breathing better. I did not mention in this post but as part of my quest to get rid of the smoking I had replaced the Turbo a couple of days ago which had reduced the smoking by 60% approximately. I had also replaced the MAF to see if it eliminates the rest of the smoke but I will be putting the old one back on. I think that the CATs probably caused the Turbo to pump oil in the air intake in the first place however it was spinning just fine. I did not notice any smoke today while out on my booting rampage. I shall monitor it for a couple of days just to make sure it is as good as I am thinking it is.

Regards and thanks to all,

Asif.

 

[glojo]

Hi Asif,
Just noticed your location, what type of diesel is going into the fuel tank?

Most of these modern CDI engines are optimised for the very latest low sulphur diesel. Is this readily available and has the car always used it?

I am NOT being racist in my comments although some folks will no doubt take my question as being just that?? (The USA are only just getting their act together on this subject)

Good luck in getting the problem resolved although it looks like numerous new parts are required.

John

 

[Asif Kazani]

John, unfortunately the diesel available here in Pakistan is very high in Sulphur. However, there is a government owned company PSO (Pakistan State Oil) the operates nationwide and sells a diesel which they claim is low emission. They call it Green XL. All the other companies here i.e. Shell, Caltex and Total have just Diesel. The difference that I could visibly notice in the former vs the latter is the absence of head/suds on top at filling up i.e. the diesel tends to settle immediately when poured. A few years ago, even at PSO, when diesel would be dispenced from the pump, it would take a while for the suds to go down vs now at PSO, it pours and settles without any suds of top. Thinking about what the company claims, it may be low in Sulphur compared to others available here but still higher vs international standards.
The irony is that my car, was an official import and not a grey import. What was DC thinking?? As for now, the car is runnning sweet and I believe that the Turbo was the only thing that took the beating upto now with that choked exhaust.

Regards,

Asif.

 

[glojo]

Hi Asif,
Thanks very much for a most informative reply. I'm sure your beautiful country would not import CDI powered vehicles unless they were happy with the quality of the fuel. I do feel however that lesser quality fuel is not doing the engine any favours.

The cricket by the way is quite exciting, Mohammad Yousuf has scored a great double century (that's if your interested in cricket)

Good luck again,
John

 

[Asif Kazani]

John,
Believe me, the sole distributors here, Shahnawaz Ltd., who have been associated with Mercedes Benz before the country came into being i.e. approximately 59 years, but unfortunately, they have not been quite active since these cars are prohibitingly expensive here. Most of these cars here are grey imports. Things have changed a little lately, but Mercds are still quite expensive here, more so if imported through Shahnawaz Ltd; I personally believe that poor fuel quality aside, they may not even keep DC updated about this for the want of service business they desperately need. The cars are so few that if they keep running right, the dealership would not be able to meet it's expenses. I checked a few weeks ago with a service advisor there about CAT replacement and he did not know much.

Regards,

John.

P.S. I definately watch cricket, I have to even when I don't want to since my son is also hooked on to it!

 

[andreas_t]

Hi guys,

Just to add my penny's worth to what Asif has already found. My CDI had the same problem as Asif's - documented in a couple of threads here. About six weeks ago I went through a manic bit of acceleration (went to overtake a bus, only to find two more cars in front of it and a BMW flying down the other way towards me !). So I booted really hard, got a HUGE puff of smoke out the back (it engulfed the double-decker bus) and voila :bannana: the next day the car is going sweet as a dream, consumption is back between 45 and 48 mpg on m-way runs and NO SMOKE !

Looks like I managed to tunnel through the block in the CAT. By the way, MB had already diagnosed new catalyst, but I was hesitant to change it due to high cost of repair and the amount of guesswork on their part up to now.

Anyway, the car is running really well now. Last week I did the front brakes and put it through an emissions test - no problems, all readings really low. In the meantime, I'm running it up and down the country and have clocked nearly 3K m-way miles.

I am going to change the CAT when I can put the £530 plus fitting together, or find someone who can do me a custom-fit for a reasonable price. In my case, the car ran with faulty injectors for 2 months, so I guess that was the source of the blockage in the CAT. It's going in for its service to MB soon and will see what they come up with this time

The motto of the story is, however, if something goes wrong with the injection system, it is the exhaust that seems to get it in the neck .... such is life.

 

[Dieselman]

Asif
I'm not surprised to read what your problem has been given the muck that you feed your car on.
I am sure you have done the right thing by removing the cats, especially the pre cat near the engine. They have a tendency to blow bits back into the engine if they bolck and the core comes loose in the housing.

Diesel cats do not work in the same way as petrol cats anyway so you aren't going to make any real difference to the emissions. Diesel cats are 2 way oxydisation cats whereas petrol cats are 3 way converters.

I bet the car sounds nice now and goes much better.

Given the fuel problems you have suffered from I would be inclined to fit some gauges to your car to monitor the health of the engine. Four gauges would be best, vacuum gauge on the fuel feed pipe, pressure gauge in the exhaust after the turbo, vacuum/boost gauge from the inlet manifold and an EGT gauge into the exhaust manifold.

In the case of your blocked exhaust you would have seen high pressure in the exhaust and very high EGT temperatures as the engine had to work much harder and couldn't pass as much cooling air.

 

[glojo]

Asif
I'm not surprised to read what your problem has been given the muck that you feed your car on.

Perhaps I was slightly more tactful?

As usual I reckon your spot on with the diagnosis and it might highlight how lucky we are to have low sulphur fuel.

There are warnings and advice about using diesel with a sulphur content exceeding 0.5% by weight (I believe this is quite high??) Changing the engine oil every 4600 miles (7,500km) Is one recommendation. Giving it a blast also helps clear the old bronchial tubes

Good luck
John

 

[Asif Kazani]

The car has had oil changes every 5000 km. However, when I switched to Mobil 1 at the last oil change, the dealer recommended that it be changed every 10000 km. This is keeping in mind the extreme conditions we drive in. As for the blocked CATs, I bet that the few cars that are here, are all suffering from this syndrome and may end up as junks after their frequent trips to the dealer till their owners figure out that the dealers are going to cost them more than their cars would fetch if sold and that they would still be doubtful if the cars would be done right. I just hope that it keeps running as sweet as it is now, especially with the Turbo singing it's sweet song full volume!!

 

[andreas_t]

Does anyone know the legal / MB implications of having the CAT cores removed in the UK ?

Also, would one remove just the pre-CAT or both ?

Given the more than significant cost of having another MB CAT fitted, I wouldn't mind just removing the existing cores and running on an empty blowpipe !

Comments /advice anyone ?

 

[glojo]

The car has had oil changes every 5000 km. However, when I switched to Mobil 1 at the last oil change, the dealer recommended that it be changed every 10000 km.

I just hope that it keeps running as sweet as it is now, especially with the Turbo singing it's sweet song full volume!!

I can see your grin of satisfaction from here. It sounds like you are very satisfied with the car and if it were mine, I think I would change the oil at the very least every 7500km. Spoil the car, it deserves it.

Happy motoring,
John

 

[Satch]

EU diesel target specification for 2005 was Sulphur content of 50 parts per million(ppm) Between 2005 and 2009 EU Directives mean that Ultra low Sulphur Diesel will have to be replaced by sulphur free diesel with 10ppm or less.

Sadly in some parts of the world (and I understand this is true in your country) diesel with a Sulphur content of 10,000 ppm or more is sold and sometimes the fuel can be of poor quality in general. Sulphur combustion products will choke catalytic converters up and prevent them from doing its job: with no access to low sulphur fuel you are better off without them.

This is why many of the old diesel engines simply could never have the ability to manage their emissions very well – they were designed for a fuel with a high sulphur content and actually depended on the SulphUr compunds in diesel to provide lubrication.

So on the positive side one thing you are unlikely to suffer from is diesel injector & pump wear!

Edit: do change the oil frequently: Mobil 1 may be a full synthetic oil with good lubrication properties, resists thermal breakdown better and is designed for extended oil changes, but only where low Sulphur fuels are used.

It will be not that much better at coping with Sulphur combustion product contamination than more conventional oils. Danger is that your engine oil becomes acidic.

Personally I would use a quality semi synthetic and stick to your 5000 km oil change routine.

 

[silverarrow]

asif use injector cleaner as well if you can get it

 

[glojo]

asif use injector cleaner as well if you can get it

What would be the best additive for Asif to use?

John

 

[Asif Kazani]

I've been using Redex Diesel Injector Cleaner, I believe it is a blue labeled bottle.

Regards,

Asif.