Exhaust problem
I have a 1991 manufactured SWB300GE petrol and a small leak on the downpipe of my exhaust. It's just before it bends to becomes horizontal before it enters the CAT. It's where one of the welds is that attached the heat shield and presumably this weld has weakened the pipe.
Question(s)
I appreciate that you can't see it but might it be possible to repair the weld thereby re-securing the heatshield and mending the leak?
Is the downpipe a part that I should definitely get from MB if the weld isn't repairable, if so does anyone know the part number
Is the part from MB pretty much the same as I would get from an exhaust centre (there's an ATS in my town)
Any suggestions much appreciated.
In order to effect a repair or a weld, the down pipe needs to be relatively sound which I expect it would be, the matter being is the hole or leak area accessible to lay down a weld alternatively patch the area up with liquid metal. I am not sure about the reference to the heat shield or is it the outer skin of the cat or exhaust you are enquiring about. I thought the heat shield was attached to the floor of the cab. The labour of the repair could tip the balance in your decision as you need to ascertain if the downpipe will be lasting and not have rot away shortly after the weld.
If you need a downpipe, this is a dealer part only and not available through the likes of ATS.
I think you meant, Rakesh.
the original heatshield was a composite fibre/aluminium foil affair that would disintegrate. the new version is dimpled. aluminised steel and quite expensive, around £100 for that part , IIRC.
It should indeed be attached to the sub-floor by a number of self-tapping screws. The down-pipes are available as dealer parts; however, I would probably get some manufactured from stainless steel, if you need to change them. The original items are of a durable steel, but not stainless and they rust away. just changed my whole exhaust system 2 years ago (all original MB parts) and the parts are again all rusty. They have not updated the design for the 300GE to stainless even though many subsequent MB cars appear to use stainless systems.
Ooops! Sorry Rakesh 
Just looking back through the paperwork that came with the car when purchased and I notice that the previous owner had the exhasut replaced with a stainless steel version but only from the CAT backwards. Is that a normal procedure? Are the downpipes particularly difficult to make in stainless?
Also, this car was actually manufactured in 1991 and I understand that this means it is not compulsory to have a CAT fitted. Is there any benefit to not having a CAT? Would it make sense to have the downpipes manufactured in Stainless and made a bit longer to delete the CAT? Not sure of the lifespan of a CAT and therefore how long it might be before the prospect of buying a new one which might be avoidable.
A proper exhaust place that makes them from scratch should be able to help you, probably needs brazing rather than welding, having same issue with my diesel downpipe, a weld given way. Think only a patch brazed on will last. Exhaust past lasts about 5 minutes before it blows out
The catalytic converter is a major restriction on that engine. You will get another 7 HP without it. The original exhaust, including down-pipes is not a quality item. The pair of downpipes are a simple design that attach to the exhaust manifold at one end and the catalytic converter at the other. Very easy to replace. There is only one O2 (Lambda) sensor before the catalytic converter and it screws into one of the down-pipes. you will need to retain that, but as it's before the cat, rather than after it, removing the cat will have no effect on the KE Jetronic fuel injection system. The catalytic converter in this arrangement is a passive device.
.
Thanks Arnie,
So, if it were you, would you have new extended downpipes made in stainless steel and get rid of the catalytic converter?
I can't remember now why I think that cars manufactured in 1991 (and presumably prior to that) do not have to have a catalytic converter. Does anyone know if that is definitely correct (before I go and get rid of it and then fail the MOT because I don't have one)?
Ouch! - I just got a quote from MB for the downpipe and it comes in at £612 plus VAT plus the various nuts, bolts, spacers, springs necessary. Now I know why that previous owner only had the exhaust from the CAT backwards replaced.
Well, mine is a 1996 version so don't have that luxury. If I were you. I would check the regulations carefully and then have a new set of stainless down-pipes made to exactly the same pattern as the originals, and in addition make another piece, which is a two-tube-into-one, to replace the existing catalytic converter. That way you keep your options open.
(what i do like on the original exhaust is the pipe-clamps with wedged seals on the catalytic converter, none of these U-shackle affairs found on replacement exhausts)
My GES300 was first registered in May 1993 on a K which means it met the cat standard of the time but having enquired from Merc as to when it was actually built it turns out to be in October 1991 and a cat though fitted was not a legal requirement. I paid Merc £25 for an embossed letter giving its build date and removed the cat, that was at least 10 years ago. Despite the removal of the cat the engine still reaches the '92 on emissions standard. I have also deleted the final exhaust box and despite this and probably because of the car's on chassis construction its still very quiet. People with K and L plate G-wagen cars should check the build date because the car was at that time an unpopular alternative to the Range Rover and it sold poorly and if mine is typical it sold slowly too
Mine the same - built in 1991 but UK registered in 1994.
But I went to a stainless steel exhaust place yesterday to see about getting the downpipes made in SS and I asked the question about deleting the CAT but the MOT man said I had to keep it even though the car was made in 1991 it is the first registration date that counts as far as CAT requirement is concerned.
So how do we find out what the definitive answer is?
Mine passes without the cat being fitted, passed its MOT on Wednesday, [CO 0.771, HC 388,] or you make a s/s exhaust box demountable in the place where the cat is fitted, if you make it a twin exhaust box you can let it exit from the right
Euro 1 emissions limits (petrol) CO: 2.72g/km HC + NOx: 0.97g/km
Here is your definitive answer
https://www.gov.uk/government/uploads/system/uploads/attachment_data/fil...
This is the literature used to MOT test.
Thanks for that David.
Must admit to not reading every word but looks to me as though as a vehicle with first use (registered) post 1992 and not listed in the Appendix that I can't delete the cat.
But more than happy to be told otherwise by anyone.
Maybe they have very accommodating MOT inspectors in Glamorgan.
Looks like it doesn't matter when manufactured. It's when first registered (used from)
(I recall BMW had to sell off quickly a number of S71-engined, V12 Models, manufactured in 1995 as after that, from 1996, they would no longer comply with new emissions standards.)
So if the car was sold after 1st Aug 1992, it needed to be compliant and therefore have the catalytic converter, even if it had been manufactured any number of years earlier.
The above MOT reference document says
'....FIRST USED FROM 1 AUGUST 1992 AND EQUIPPED WITH ADVANCED EMISSION CONTROL SYSTEMS ...'
Arnie
You are correct with that statement , but the 300ge wasn`t equipped with an advanced emission control system, it refers to closed loop lambda controlled systems , hence no 1990s UK petrol W463s are listed in the document as they were all Bosch CIS. I still get in 1995 minis with a carb and cat which are still tested at 3.5% CO,
As a tester if i was presented a 300GE with out a Cat i would test it at 3.5% CO as its not compliant to a full CAT test due to its design.
The Bosch KE Jetronic, as fitted, is a closed-loop lambda system. However, the O2 sensor is before the catalytic converter, so the emissions are not tuned in a manner requiring the catalytic converter. in fact all it will do is help burn any HC's remaining, but have little effect on anything else. and because it's located in what would be today, miles from the exhaust manifold, it takes ages to warm-up and so has little effect in reducing the smell of unburned fuel when starting then engine from cold with a rich mixture.
But, yes, i see what you mean, that this is not a closed-loop control around the cat as in a more modern system, with sensors before and after to optimise emissions with the cat.
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Thanks Arnie,
At some stage in it's life someone has welded some heat shield to the downpipe.
The heat shield that should have been attached to the bodywork isn't there.
Have tried taking a couple of pictures - not sure how revealing this one is.
Will go and see my friendly welder and see what he has to say.