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OM642 oil leak on passenger side

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Old 06-07-2020, 05:06 PM
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2012 S350 Bluetec 4MATIC; 2011 ML350; 2005 C230k;
OM642 oil leak on passenger side

I have engine oil leak on right/passenger side which I can't track. The leak is not from oil cooler. I have inspected the engine block with endoscopic camera, everything above engine mount bracket is dry. If I look from under the car, I can see the leak is coming from area between engine and front differential. Does anyone has any clue where the oil may come from?
Old 06-09-2020, 10:57 AM
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Ml350 bluetec
Might be coming from the back of the block, ie facing the firewall. There is a Oil and Air separator(PCV) that is bolted there. This is the piece if you have a newer OM642: https://www.pelicanparts.com/More_In...=0&SVSVSI=7323
Old 06-09-2020, 12:13 PM
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2012 S350 Bluetec 4MATIC; 2011 ML350; 2005 C230k;
PCV is new, I replaced it two months ago, and it is not leaking from there. I'm suspecting upper oil pan, or through the screw which is holding crankshaft bearing cap, but this is very unlikely. I want to be 100% sure because it is very intense job to remove upper oil pan. As far as I know there is no weep hole on that side of engine so the leak has to be from outside.
Old 06-09-2020, 06:01 PM
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W211 E320 Diesel OM642
Engine oil fill cap washer? I would wash the engine bay first and then get an inexpensive remote camer and see where it's coming from.
hth
Old 06-09-2020, 07:25 PM
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If it was leaking from the oil fill cap, it would be really obvious. I had an oil leak from the filler cap washer, and it left an oil stain there.

Oil cap filler cap.
Old 06-09-2020, 07:44 PM
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2005 E55 AMG - Weistec Supercharged, 1994 Nissan Skyline GTST (650whp), 2012 E350 4-Matic (Wifeys)
The timing chain tensioner is on that side. Behind the alternator, basically 10 inches under the oil cap. It’s sealed with a crush washer like any normal oil drain plug. I’ve seen them leak. Also, intake lines, boost hoses etc. Brake boost the engine with someone who knows what they’re doing looking for boost/oil leaks. Do you have pictures? Best bet is to clean it with brake clean, and I like to use leak trace powder. It’s a sprayable powder that turns white when it drys, and makes any leaks super obvious because they turn the white powder dark/wet
Old 06-09-2020, 11:37 PM
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2012 S350 Bluetec 4MATIC; 2011 ML350; 2005 C230k;
It is not from tensioner I already check that. Thanks for the sprayable powder suggestion I'll try that. I don't have photo of the leak, I'll try to take some photos this weekend. Here is photo of similar engine. Basically everything above red line seems to be dry. But if I look from under the car there is oil between engine block and front differential.

Old 06-10-2020, 10:59 AM
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Originally Posted by Etienne Lau
If it was leaking from the oil fill cap, it would be really obvious. I had an oil leak from the filler cap washer, and it left an oil stain there..
keep in mind that most of the time, you drive the car at great speeds. The car does not sit idle...
Old 06-10-2020, 11:05 AM
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Originally Posted by GoodByeHonda
keep in mind that most of the time, you drive the car at great speeds. The car does not sit idle...
Don't see how idling vs driving has anything to do with oil leak from the oil filler?
Old 06-10-2020, 11:06 AM
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Having worked on these engines since they’ve come out, I have about 50-60 oil coolers under my belt. The line you drew looks like it’s probably a boost pipe or O-ring leaking. Do like I said, clean it really well and leak trace powder the front/side. Brake boost the engine and start searching for traces of oil
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Old 08-09-2020, 06:06 PM
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Ml350 Blu tec
Hi I also have a oil leak on the passenger front area of the engine, its seems wet under the housing that the engine oil dipstick bolts to . I dont know what that thing is ?? the large black hose is also there? is this the oil cooler ? or is the boost pipe ?? Thanks in advance, Joe

Last edited by Jxp; 08-09-2020 at 06:08 PM.
Old 08-09-2020, 06:30 PM
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Pictures will help. Passenger side or driver's side? The oil dipstick in the US in on the driver's side and not on the passenger side.
Old 08-09-2020, 06:46 PM
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Ml350 Blu tec
This is a 2011 ml350 Blu tec diesel in the USA, I will get a picture later , Thank You!
Old 05-31-2023, 06:21 AM
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Hello, i had simular oil leak from my om642.826, rear of engine, rigth side behind engine and gearbox. This leak driv me nuts in two years, becauce i could not figure out. Cooler was sucpect, but i used boroscope, and it was not the cooler. Replaced turbo inlet seal (big red) but did not help. I finally find out, it was the backside of the oilcap at engine was leaking. The o-ring in the cap was hard / bad. Over time oil go backwards, and rear of the rigth sylinder head behind the rear right injector its a drain hole. This hole ends up at rigth side between engine and gerabox.
Old 09-16-2023, 10:58 PM
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2013 GLK250 Bluetec & 2014 E550 Cabriolet
I have been driving my car without the splash cover since I fixed this issue. The rainy season is about to come, I lifted my car to reinstall the cover. Interestingly the drain plug was again leaking the oil very very little (no drops on my garage floor, but around the drain plug, it was slightly wet with engine oil). I applied proper torque when fastening the drain plug (30Nm).

What could be possible reasons it leaks again? Maybe the guys who worked on engine oil applied too much torque (I don't think that they used a torque wrench) and messed up the plug?

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