Hello, I'm new here and would like to pick the communities collective brain if I may? I am the proud owner of a C320 CDI on a 58 plate. I have lately discovered a slight burning/plastic smell from the front of my car after taking it for even just a short run. I can smell it as I walk round the nose of the car and it is noticeable from both sides at the arches too. There is no smoke nor warning lights. The car has the OM642 engine and was wondering if there were any common items I should look at? Any input is gratefully appreciated.
Slight smell OM642
- Thread starter R1ley
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MrGreedy
MB Enthusiast
I have the e350 OM642. I have a bit of oily mess on the top of the back of the engine on the LHS (passenger side) near to the turbo. It's taken 85k miles to get a bit filthy, not terrible, but at some point I need to get the engine cover off, clean everything up, and then inspect it every week to see if it makes it earlier to identify.
I'm also going to try holding a fine feather around that area to see if I can see any 'puffing', or if we get a very still day, one of those smouldering insect repelling smoke sticks to see if the smoke is blown around. Good luck. Hopefully easy to find something that can be resolved.
I'm also going to try holding a fine feather around that area to see if I can see any 'puffing', or if we get a very still day, one of those smouldering insect repelling smoke sticks to see if the smoke is blown around. Good luck. Hopefully easy to find something that can be resolved.
Note that at about that mileage the oil cooler seals are prone to failure on the OM642. The oil cooler sits in the V of the engine and needs a major stripdown to get to it.
Small rubber seal but it is an immense job to get to the oil cooler and replace it / seals, hence very expensive job.
Or it could be the orange turbo seal seeping oil....that one is an easy fix.
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@MrGreedy Or, as it is the passenger side, it could also be leaking o-rings on the turbo to intercooler pipes as well as the air supply to turbo seal. Best bet is to clean everything off and then see where it is coming from. I had one split ring and when I followed the pipework I found oil mist at a couple of other joints so replaced those as well - certainly improved performance. I doubt it would have shown up using a feather, the best method is to just strip them down.
Unlikely to be oil cooler as this tends to show underneath the car rather than on top of the engine.
Unlikely to be oil cooler as this tends to show underneath the car rather than on top of the engine.
MrGreedy
MB Enthusiast
Trying to keep on topic and not wanting this to hijack the OP's thread, but I guess it's all oily mess/slight leak identification around the engine.
I don't think mine is oil cooler seals. If it was that, I would do it myself soon, and at the same time clean out the inlet manifolds of all the carbon rubbish/gunk. This is a job I'm intending to do anyway. Probably next summer (the inlet manifolds) so I'll do cooler seals at the same time for piece of mind.
Turbo seals down the back end of the engine are all pretty new. From the location, the nearest seal to the filth is the EGR/seal. I'll clean up the EGR and replace the seal anyway.
I don't think mine is oil cooler seals. If it was that, I would do it myself soon, and at the same time clean out the inlet manifolds of all the carbon rubbish/gunk. This is a job I'm intending to do anyway. Probably next summer (the inlet manifolds) so I'll do cooler seals at the same time for piece of mind.
Turbo seals down the back end of the engine are all pretty new. From the location, the nearest seal to the filth is the EGR/seal. I'll clean up the EGR and replace the seal anyway.
If you’ve had it to bits recently the green O ring that seals the aluminium boost pipe to the turbo outlet is notoriously difficult to fit without nipping it. I’d be taking a look at that first. Very common. Grease it up generously and try to keep the pipe as horizontal as possible while pushing it on
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Oil cooler seals is a big (labour) job and really only an issue on 2009 E350 (and probably C350). They changed the seals after that.
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I just noticed that you have a 2008 with a '320' engine, and I can't honestly say I know about the oil cooler seals on those models - I just know the issue was resolved by 2010. Look under the car for signs of leaks there.
If the car has had leaks in the past, it could be the residue on the engine, and then the engine gets hot and makes the smell worse.
It's most likely a turbo or fuel seal of some sort that is letting out oil or diesel in liquid or vapour form. I've had all sorts of leaks, and they've all been (relatively) easily fixed, so far.
Also, as you mentioned burning plastic - it's definitely not a DPF regen, is it?!
If the car has had leaks in the past, it could be the residue on the engine, and then the engine gets hot and makes the smell worse.
It's most likely a turbo or fuel seal of some sort that is letting out oil or diesel in liquid or vapour form. I've had all sorts of leaks, and they've all been (relatively) easily fixed, so far.
Also, as you mentioned burning plastic - it's definitely not a DPF regen, is it?!
R1ley
Member
Quick update, no oil leaks are visible however it does indeed have a slight leak on injector no2 on the right hand cylinder head. Have ordered the parts required and will be getting the job done very soon. Thank you again to everyone for all your input and advice. 
R1ley
Member
OK, its been a while since I have updated this. I got the injectors re-sealed and noticed that there was a fair amount of oil weeping from the intake/turbo join. Turns out, the intake was badly cracked and allowing the oil vapour to escape and condense into liquid dripping onto hot engine and creating the burning smell. So, I have removed the damaged part and fitted a silicone hose, also fitted a catch can to stop the turbo ingesting all the oil vapour and it clogging the inlets. I have on order several seals and gaskets and plan to strip the top of the 'V' and clean all the crud away, whilst doing this I will also replace the oil cooler seals and clean out the inlet manifolds too. Hopefully this should all allow me to enjoy my car without having to worry about anymore smells, and prevent any issues with the inlet manifolds in future too.
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Do you have a picture of your nodded air intake?
I bought a silicone seal from turbo zentrum for £30 or so, but cancelled the order when I realised that I had to dremel the current one. Mine is a bit broken but if I change the orange seal every 5-6 months, it’s fine.
I bought a silicone seal from turbo zentrum for £30 or so, but cancelled the order when I realised that I had to dremel the current one. Mine is a bit broken but if I change the orange seal every 5-6 months, it’s fine.
MrGreedy
MB Enthusiast
You might also want to change the PCV hose/pipe, which might cut down on the amount of oily vapour that is passing the valve. I've been looking at this type of general issue way too much over the past month, and the PCV pipe/valve should really be considered a 60k consumable item on the OM642.
As it turns out, when I said in post #10 mine wasn't oil cooler seals.... it turns out that a well respected independent specialist thinks it's almost certainly oil cooler seals
Oil cooler seals tend to go from minor to horrific in a short space of time. Mine is currently still a minor leak, but I'm speccing up the job at the moment, but given the time of the year I'm leaning towards paying for it.
I've got oil creeping up the intakes. I also had the 'green o-ring' not seated properly that seals the turbo outlet to the long metal pipe on the top of the engine. That has also resulted in blow-over of oily residue on the top of the engine.
I also had a conversation with someone this week who has a lot of experience with these, and they suggested that it might not be down to the seals at all, but rather due to heat cycling an inevitable micro movement of the oil cooler against the block (due to expansion and contraction) whereby tiny amounts of oil and gunk get trapped between the mating surfaces. This dries over time, and it then compounded by more tiny tiny amounts of oil and gunk finding its way in, and effectively 'jacking' the cooler away from the block very very slightly. This then causes the leak, and no amount of seal redesign will change this. The conclusion: the oil cooler seals might be a regular 60-100k issue. A lot of these cars are not going to be reaching or exceeding the 150-200k mile mark, so multiple oil cooler seal changes wouldn't register.
There's some good links here 2012 E350Cdi 100K Mile Service | Engine
Also, FCP Euro show 3rd party seal kits for this job, and list out all the Mercedes part numbers. That's a good starter if you are doing it yourself as to what seals you will need.
If you've had oil leaking down (on to or in the vicinity of the swirl flap motor), it's probably worth while replacing the swirl flap motor (£150) whilst you're in there.
The other thing to consider is getting a new oil cooler at the same time. It has been know that specialists have done this job, only to find the leak persists and it was a tiny crack in the cooler.
Good luck. Keep us updated
As it turns out, when I said in post #10 mine wasn't oil cooler seals.... it turns out that a well respected independent specialist thinks it's almost certainly oil cooler seals
Oil cooler seals tend to go from minor to horrific in a short space of time. Mine is currently still a minor leak, but I'm speccing up the job at the moment, but given the time of the year I'm leaning towards paying for it.
I've got oil creeping up the intakes. I also had the 'green o-ring' not seated properly that seals the turbo outlet to the long metal pipe on the top of the engine. That has also resulted in blow-over of oily residue on the top of the engine.
I also had a conversation with someone this week who has a lot of experience with these, and they suggested that it might not be down to the seals at all, but rather due to heat cycling an inevitable micro movement of the oil cooler against the block (due to expansion and contraction) whereby tiny amounts of oil and gunk get trapped between the mating surfaces. This dries over time, and it then compounded by more tiny tiny amounts of oil and gunk finding its way in, and effectively 'jacking' the cooler away from the block very very slightly. This then causes the leak, and no amount of seal redesign will change this. The conclusion: the oil cooler seals might be a regular 60-100k issue. A lot of these cars are not going to be reaching or exceeding the 150-200k mile mark, so multiple oil cooler seal changes wouldn't register.
There's some good links here 2012 E350Cdi 100K Mile Service | Engine
Also, FCP Euro show 3rd party seal kits for this job, and list out all the Mercedes part numbers. That's a good starter if you are doing it yourself as to what seals you will need.
If you've had oil leaking down (on to or in the vicinity of the swirl flap motor), it's probably worth while replacing the swirl flap motor (£150) whilst you're in there.
The other thing to consider is getting a new oil cooler at the same time. It has been know that specialists have done this job, only to find the leak persists and it was a tiny crack in the cooler.
Good luck. Keep us updated
