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Old 02-01-2019, 09:02 PM
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Join Date: Sep 2011
Location: Minnesota (Minneapolis)
Posts: 32
2012 GL350 OM642 Oil Cooler Leak or not?

Hello All,

Looking for some advice as to where to start. I have a 2012 GL350 with a pretty bad leak. It was first diagnosed by my local mechanics as the infamous oil cooler leak (not Mercedes shop, but I've used them forever and I trust they would not intentionally steer me wrong). They indicated they were not too excited about taking that on. I have some experience turning a wrench so I spent a weekend and did the cooler seals. Only problem is that it is still leaking pretty bad. I am now starting to wonder if something else is leaking.

The leak appears to be more from the front driver side of the vehicle. From what I understand the oil cooler leak usually presents back of the engine. This leak is dripping about in line with the front tires, and slightly to the driver side of middle.

Attached are a few photos. Wondering if there is something else I should be looking into? Any help is appreciated.

Oh, and to clarify the front of the engine had been cleaned up when I did the oil cooler seals (also did timing chain at the same time). As such, the oil you see in these photos is from the last month (2000 miles).

Current Ride: 2012 GL350

Past Rides: 2004 E320, 1987 300SDL

Last edited by ccrobin; 02-01-2019 at 09:22 PM.
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Old 02-17-2019, 09:16 PM
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Join Date: May 1999
Posts: 34
don't know what's causing your leak, but just wanted to say great job to replace the oil cooler seals yourself!
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Old 02-27-2019, 12:16 PM
iwrock's Avatar
Join Date: Nov 2003
Location: Hella NorCal
Posts: 3,312
The oil cooler drips down the back of the engine - there's a drain hole at the back of the V. I had the oil cooler done at 130k miles, then at 155k had the crank case breather fail and cause failed oil cooler like symptoms.

It's hard to get a good look at the pictures (they're cropped), but am wondering if you potentially have a front main seal leak. Can you share links to the full sized images?

And hats off to you - the timing chain and oil cooler are the Achilles heel of the OM642. I'm reluctant to dig that deep into the engine, I don't have the patience to tackle a 8+ hour job anymore.

01 Honda S2000 - dogs dd
07 MB ML320 CDI - dd
16 Lexus IS250 - wifes dd

it's automatic.
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Old 07-12-2019, 01:38 PM
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Join Date: Jul 2019
Posts: 4
I have a similar leak on my 2010 GL350. I also had timing chain done a few thousand miles ago so everything else should be sealed up. It was diagnosed as the "charge air pipe" leaking just yesterday. P/N 642-090-16-37.

Just found this thread;

OM642 oil leak at front of engine

Last edited by TGcville; 07-12-2019 at 02:19 PM.
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