W221 S320Cdi oil leak

[PaulMason]

Hello all, my 2009 S320 has developed oil incontinence. Has started in the last week or so and appears to be from the back of the engine. As yet, I have not taken the undertray off but intend to do so this weekend. My question, to help me properly diagnose, is there anything particular I should be looking for?

From the initial research, 2 culprits being oil cooler seals and oil separator. I'll be trying to look at both, but suspect the cooler seals won't be accessible based on location. The oil sperator was changed about 2 years ago (so suspect it's not that). Any other main causes (my R171 had a similar leak but that was the expansion plugs in the back of the heads which was a doodle to fix).

Any recommendations of what to be looking out for to determine the cause. Car has been running bob on having had some injector seals replaced a few weeks ago though seems to be a bit smokier than usual at the mo

TIA

 

[Dodipops]

V6 diesel I presume?

Oil cooler most likely, there is weep holes in the block one at rear passenger side one at front.

These holes are designed to let leaking fluids out from between the V, so a good clean off and watch for the oil coming from there, if it is then it’s from with in the B and most likely cooler seals.

 

[PaulMason]

Sorry, yes , V6 diesel OM642. Thanks for the steer, I'll clean it all off and see where it comes out of. I'd maybe best start getting myself prepped for a couple of days work.....

 

[W1ghty]

When I changed my om642 fuel filter the other week (when the filter was out ) , it did look like I could see the side of the oil cooler below with a torch .

 

[PaulMason]

When I changed my om642 fuel filter the other week (when the filter was out ) , it did look like I could see the side of the oil cooler below with a torch .

Thanks W1ghty, I'll be getting the undertray off at the weekend for a place ke around. The turbo and oil separator seals are fairly fresh (c. 500 miles) the oil separator itself a couple of years old, so likely not them. Which leave the oil cooler as the most likely culprit, which is at least cheap to fix in terms of parts lol. Best get myself onto the weather app and a few days booked off work!

 

[PaulMason]

UPDATE: it is NOT engine oil. Put some cardboard underneath and there is a leak of clear, possibly golden ish, viscous, though quite thin liquid. Based on location and all levels (brake fluid etc) being fine, thinking gearbox oil. So, I'll get the cover off, check sump, gasket (though changed c. 5k miles ago) and anything else that's around (guessing cooler lines and electronic connectors). Car has almost 160k on it now so may be as simple as a porous sump

 

[BlackC55]

Could it be a diesel leak? Fuel filter pipes are very common.

 

[PaulMason]

Could it be a diesel leak? Fuel filter pipes are very common.

Hmm, now hadn't even thought of that.....now you say it, actually I kicking myself as a) the filter was changed about 500 miles ago and b) to he filter housing had a bit of diesel on top of it, so wondering if it's leaking from their and working its way down. I will check the fluid again on the cardboard but it was thinner than I expected

 

[BlackC55]

That sounds like a fuel leak.

Get new pipes and clips from MB ONLY!

 

[PaulMason]

That sounds like a fuel leak.

Get new pipes and clips from MB ONLY!

Thanks BlackC55. Just cleaned the top of the filter up and started the car and staright away, drip drip drip from the return side. Going to strip the pipe off this weekend and replace and add a jubilee clip

 

[W1ghty]

Thanks BlackC55. Just cleaned the top of the filter up and started the car and staright away, drip drip drip from the return side. Going to strip the pipe off this weekend and replace and add a jubilee clip

Don’t use a jubilee clip buddy , get a clic-r clip from MB

 

[W1ghty]

I had a diesel leak when I fitted a new fuel filter last week , I cut the last cm off the pipe , reconnected it and no leak . I’ve ordered new pipes from MB which I’ll fit next time

 

[PaulMason]

I had a diesel leak when I fitted a new fuel filter last week , I cut the last cm off the pipe , reconnected it and no leak . I’ve ordered new pipes from MB which I’ll fit next time

Thanks W1ghty. Do you by any chance have the parts no's for the pipes as just got off the phone with parts at my local MB and they weren't sure which pipes I meant (maybe "the rubber ones which connect to the inlet and return on the fuel filter" wasn't clear enough of me) so I'm heading down with the car in the morning so I can show them

 

[W1ghty]

A6420700281 high pressure line to filter
A6420781281 short hose to filter
A0069971890
A0049972090 are two different size clic-r connectors to the filter

 

[W1ghty]

Thanks W1ghty. Do you by any chance have the parts no's for the pipes as just got off the phone with parts at my local MB and they weren't sure which pipes I meant (maybe "the rubber ones which connect to the inlet and return on the fuel filter" wasn't clear enough of me) so I'm heading down with the car in the morning so I can show them

Double check these are right for your model , they should be the same as mine .

 

[PaulMason]

Double check these are right for your model , they should be the same as mine .

Parts ordered, arriving Weds so probably a job for next weekend. I got the in and out for the A6420701681 and A6420781281

 

[PaulMason]

Now have all the bits. To do the return pipe, from the filter to the pump, it looks like the intercooler pipe has to come off to get the bolt on the return pipe bracket. Undid the long bolt that doubles as a engine cover mount, did the little torx that goes onto the black plastic box at the end of the intercooler pipe and holds the large C-clamp around the alum pipe. Its loose but cannot get it off the black box. I didn't want to pry at it as its aluminium and plastic and had visions of breakages. Is there a knack? The car was warm assuming would mean the aluminium pipe expanded and made it easier to remove? Any hints and tips or do I just need to ease the end of the pipe with a flat screwdriver? Finally - do I need to take the bat wing off or is there enough clearance to get the intercooler pipe out of the way without?