Hi All, just finished replacing the oil cooler seals on my E350 CDI. Big job, wouldn't wish it on anyone. Haha.

After the first start up it quite quickly started to leak diesel from around the back of the engine. I say "back" of engine as it seems to be dripping around the sump and coming off of there. I've taken off all the bits which block the view of the injectors and injector pipework on the top of the engine and none of that is leaking, fuel filter seems dry. Nothing is spraying out the top when it's running and the engine runs perfectly smoothly.

Also the sky started leaking water...! So I've had to stop work and not yet had a chance to go under the car to look for the leak. As it isn't leaking from the injector rail and pipework I'm struggling to think where else the leak could be coming from?

Anyone seen this before or will I just have to get under the car and search for the problem? Won't be able to do that for a couple of days due to bad weather forecast.

 

I would check the fuel connections around the high pressure pump.
Not much room back there to see anything...

 

Isn't the high pressure pump engine driven and mounted on the front of the engine?

I'm wondering if I may have misidentified the fluid and it is actually coolant and maybe coming from the mount that the turbo sits on.

 

What is your CDI engine Model?
This will help us locate your fuel pump.

 

Pretty sure the setup was the same on the old straight-6 as well. I believe mine is the OM642 - it's a 2012 E350.

 

Come on man diesel fuel and coolant is so different by smell and by touch.
Dip the tissue wiping this "fluid" in water, is diesel you can see easy shiny thingy on water surface. Coolant wont do that.

Watch this video for potential fuel leak of OM642


.

 

You make a good point. I am pretty sure it is diesel but the problems with that conclusion were two things:

1. The fluid was dripping onto a rough floor which was already contaminated with oil and coolant where those fluids had leaked during the work to replace the oil cooler seals.
2. I have checked around the top of the engine in all the places mentioned in that video and there's nothing leaking around the top.

So either it's coolant leaking from around the turbo or it is a diesel fuel leak from the supply or return hose. I'm guessing though and just reaching out to see if anybody knows of a common leak point. For instance if someone were to say there's a common plastic fitting which gets strained when you work on the system and can often break then I'd be looking straight for that. At the moment the whole top side of the engine is dry and the fluid dripping out is coming out at quite a decent rate.

I should be able to get under the car tomorrow to diagnose this properly so hopefully I can see the leak easily without having to strip too much. Luckily the undertrays are still off as I've not yet finished until this leak is dealt with and then they'll go back on before the car is back in use.

 

Diesel is not this forum strong point, being USA based forum and not European or UK where W212 diesel is popular.

I am blind on MB diesel, and I tried finding for you OM642 Introduction Sheet which usually explained a lot, but could not find it on the net.

The typical engine Intro document from MB will look like this : https://www.scribd.com/document/3536...s-0M651-Engine


This kind of Introduction booklet is one of the best to use to see "things" on the engine.
Easily found on the net is M276.9 3.5NA & M278 Intro document - 1 booklet.
Also M276.8 3.0 Turbo and M157, separate booklet.


Or you go to youtube and try to find teardown or overhaul videos
I used such video often to learn what components is actually where, aside from how to tear down properly.
Spare parts catalog is never easy to imagine components location and install.


OM642 Teardown



.
OM642 overhaul part 1 - teardown


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Part 2 - Re-assembly

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Good luck finding the leak.........

 

Here are front and rear pics of your OM642...

front end


rear end

E350 V6 Diesel pump is up-front. Trace the conduits from engine to chassis to locate your leak.



undersized oil filter ??
This better be serviced early to hold diesel soot contaminants low.

 

Unfortunately the problem turned out to be a coolant leak. When running the car over some cardboard I was able to have a better look at the fluid and it's definitely coolant. So I'm looking at doing nearly the whole job again. I'm about halfway through and I noticed that a couple of the intake manifold bolts were quite lose so it is probably leaking from there.

There is also a bridge-hose between the two manifolds and it turns out that is also a weak spot which has caused many failures under exactly these circumstances. i.e. replace oil cooler seals = get coolant leak from manifold.

Here is a thread about it: https://forums.mercedesclub.org.uk/i...k-help.186884/

 

At this age the car engine is, whatever you can access WHILE IN THERE and when they are : plastic, or rubber or seal/o-ring, they are to be renewed.
If hoses uses those one time use special clamp, you need to buy the new clamps and the special plier, don't Macgyver other plier for such job. I hate such special hose clamp

Good luck on the repair....

 

Here is the evidence. The pool on the right in particular looks like pure coolant. I put a dab on my tongue just to check and it was sweet.




It wasn't the loose manifold bolts, it was the same problem loads of other people have had.

I think what happens is when you're doing this job you look at the throttle body setup on the front of the engine and you think "oh my god no, please, god no" - so you avoid dismantling the throttle body and you take the manifolds out from above and detach them from the throttle body leaving that in place.

When you reinstall the manifolds you do the left bank first as it has the EGR system attached to it. Then you drop in the right bank manifold and the two are connected with the cross-over pipe which carries coolant. The issue is with getting the little connecting pipe to seat nicely as the two manifolds are meant to press against each other and this little pipe has no fixings, it just sits between the manifolds held in place with o-rings. There isn't really enough space to drop in the right-bank manifold when the left manifold is already in place.

So this time I thought I would go to the extra trouble of removing the throttle body, it's complicated but not so bad after you've been through it once. When you do it like that you can get both manifolds seated, then push the throttle body onto the manifolds once they've been fixed down.

The picture shows where the pipe sits between the two manifolds. In my case the o-ring on the left side of the picture was pinched out of sight at the bottom of the pipe and this is where it was leaking. I changed the o-rings before refitting.

 

Sorry, as I said I am blind on MB diesel. If M276.820, I know decently well.

Good that you show photos.....

How does MB WIS specify this teardown/process ?
Surely not the "short-cut" way ...correct ?
Often MB WIS is too extensive but it is best and safest method.

Hope the leak will be cured completely.

 

I don't have access to the WIS so not sure what they would say about it. I probably do have access as I've got the Xentry diagnostics system and it has a PDF library but I'm more of a 'have a go and see' what happens kind of guy. Read the manual later if there's a problem!

I have almost finished reassembling, waiting for the weather again. For some weird reason when it was running yesterday morning before I started trying to fix this leak it didn't occur to me to put it in the garage where I could work on it safe from the weather.

I have had to almost completely redo this job. Getting the manifolds off is the last part before you take out the engine oil cooler. The only difference would be taking off the oil cooler which is held down with around 10 torx screws to the block in the valley between the heads.

 

Get Ebay's EPC and WIS, year 2020 is good enough.
My Xentry is complete system because it is from Benz Ninja, it has all EPC + WIS and is connected or linked to Xentry automatically when needed.....but...but, I do not like working on 15" laptop screen.
I also hate laptop keyboard, on all my 3 laptops.

On my PC I have ebay's 2018 WIS/EPC and from the net I got WIS only, but 2020. These are my daily EPC/WIS.
I can only work long hours on my PC and must be minimum 27" screen and must be at least 2 screens and must use my usual keyboard. I am spoilt for muscle memory for keyboard.

I am old fashion when comes to what I like using as PC stuff. I am still on Window 7 ..LOL. I hate Windows 10 or newer one, which one of my laptop is WIndows 10.

I do not want change when oldie stuff works well to my muscle or eyes/file/location memory for my PC.

The reason I am keeping my W212 E400 to at least year 20th is because I like it.
If my health is good and parts easy to come by, keeping it to 30th year could be a possibility....but at the rate MB parts inventory are so bad since Covid,
and now MB making less money being wacked by Chinese EVs..... setting my E400 on fire as New Year 2040 fire works would be more fun when parts are no more available.

 

There are a lot of parts available supplied by aftermarket retailers. I've done a lot of work on classic cars over the years and I've found you can always get the parts. Sometimes you have to refurbish old parts but one way or another the parts are always out there.

I'm the same not liking to work on small devices like laptops and hate using mobile phones for anything serious. You need to buy a thinkpad if you want a good keyboard. Traditionally they always had really good keyboards but can imagine that may have changed like everything else that was good! haha.

 

If you live in Europe or USA, and surely a left hand drive Mercedes owner, life is much easier on parts availability.

I am a right hand drive car owner, which in itself is already a bad market segment for parts which is RHD specific, like brake master cylinder and booster.
RHD car represent probably less than 10% of the world market.

My country also prohibits importing used parts/goods, I know it is stupid, but it is a way to prevent being a dumping ground for "used" products, like clothing as a simple example.

There is a "naughty-submarine" method I can use for importing prohibited used car parts, but it gets very expensive as there is minimum charge and it has to be via Singapore.

Here is me waiting for 7+ months already from MB Indonesia : https://mbworld.org/forums/e-class-w...r-rhd-car.html