Help with 2012 GL350 Oil Leak but don't think it is the oil cooler
 

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 a 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. When I got into it I found the cooler already had the purple seals. I installed the new ones anyway. While I was in there I also replaced the timing chain as I was starting to get the startup slap.

Oil is still leaking pretty bad though. The leak is evident below the vehicle slightly to the driver side of the vehicle about inline with the front tires, while another lesser drip is just slightly to the passenger side of center also in line with the front tires. From what I understand the oil cooler leak usually presents back of the engine so the marks it is leaving does not seem consistent with an oil cooler leak.

Visually inspecting from the top I see a fair amount of oil on the lower rails by the front driver side. the top of the pan along the front middle of the engine has oil on it, and the alternator area on the front passenger side has evidence of oil on it. I suspect something is getting onto one of the pulleys and getting thrown around.

Attached are a few photos. The oil is not as east to make out in the photos as with the naked eye.

Wondering if there is something else I should be looking into? Any help is appreciated.

https://cimg3.ibsrv.net/gimg/www.mbw...20a773dcf2.jpg
https://cimg5.ibsrv.net/gimg/www.mbw...86c49b3aa9.jpg
https://cimg4.ibsrv.net/gimg/www.mbw...71c804e867.jpg
https://cimg7.ibsrv.net/gimg/www.mbw...1fd06322cb.jpg
https://cimg1.ibsrv.net/gimg/www.mbw...21b7013f81.jpg
https://cimg8.ibsrv.net/gimg/www.mbw...52eb0dd49b.jpg
https://cimg6.ibsrv.net/gimg/www.mbw...63304f2442.jpg
https://cimg2.ibsrv.net/gimg/www.mbw...6b91117014.jpg

That sounds all CSI, great idea. Never done anything like that. Can I get the dye from a regular auto parts store?

Could there be an oil leak here?
 

So I added some dye, cleaned everything up, and let it run a bit. While cleaning I started suspecting it may be the oil filter housing gasket, leaking onto the serpentine belt and thus being flung all over. I didn't find any glow with the uv light anywhere near that though. Also, the leak didn't seem to be dropping. I suspect all the cleaning I did it may need to run a while more. I did, however, find a glow with the UV light on top of the fuel filter. It appears there is a bit of fluid (looks like diesel) on top of it, but can figure out why the dye would be there. Is there something that could be leaking oil at this spot, or does diesel just glow under UV? See photo attached.

https://cimg2.ibsrv.net/gimg/www.mbw...b4d269ec77.jpg

Leak Location
 

I have a 2011 and have had all of the common leaks. The leak you show in your first pics is 95% likely the oil filter housing to block gasket OR the intermediary oil filter housing gasket. Mine leaked at the intermediary gasket (which is not available by itself) and dripped a little on the serpentine belt which flung it everywhere. It even caused my belt to slip.

I bought a new oil filter housing/block gasket and it fixed it for this area. I have had oil cooler leak, oil filler cap gasket leak, intercooler hoses/orings oil leak, turbo intake gasket (orange donut) leak.

I have been leak free for about 30k miles now!

Well, I think I also have the intermediary housing leak,and you answered my question as I was unable to find that gasket. Looks like I will be looking for a new housing. See attached photo.

How difficult was it to replace? I'm not finding any videos or how-tos on it.
https://cimg3.ibsrv.net/gimg/www.mbw...3a637ae842.jpg

Thats exactly where mine leaked. The housing was not difficult to replace, there is a little bracket at the top that bolts on close to injection pump that is a little tricky. Jut plan on a good clean up when you are done, you have to remove the tensioner unit and I would replace any Serpentine belt that has had oil on it.

After I had my housing off the vehicle i think you could use a really good form in place gasket maker (Toyota brand FIPG sealant is my favorite) and make it work. They do sell the housing to block gasket. Its funny how predictable the points of leakage are on these motors, but I guess thats a good thing when you own a couple of them.

Clean, degrease, replace and roll on down the road......

New Oil Filter Housing should be arriving today. I will try to ge to it this weekend and post my results.

please post your results. I am looking at possibly leak in same area.

where did you order the housing?

Shipment had been delayed and is actually on the truck for delivery today. I purchased from a popular e-commerce site named after a South American Rainforest for $108 new. Not sure if it comes with the needed gasket so I ordered one of those as well for $12.

I will definitely post the results. I sure hope this is it because I'm tired of leaving a puddle that looks like an automobile homicide every time I park. Also tired of adding a $12 quart of oil every other day. :wtf:

Update: Parts received yesterday. The filter housing did indeed come with a new gasket so it was not necessary for me to purchase one separately. Oh well, only out $12.

In case anyone else needs to order this part, it is MB part# 6421801410.

I'll get this installed in the next few days and post some photos and an update.

So the housing change was a success. It would appear my leaks are gone. The housing arrived not only had the gasket, but came with a brand new filter installed. The replacement took about 45 minutes. Contrary to what others have said I did not need to remove the tension pulley. My approach was to remove the lower left bolt wile the belt was on, then I removed the belt and was able to get the upper right bolt (note, once the belt was off the tensioner obstructed the lower left bolt). Reinstall in reverse order - install upper right bolt with belt off, the put on belt, then install lower left bolt. I changed oil at the same time as this project and with the new oil I also added 2 bottles of the Lubri Moly Oil Saver, which has received high praises for re-sealing old gaskets and seals. The combo of the new filter housing and the oil saver seems to have solved my leak issues.

Note: I drained the oil before removing the oil filter housing and figured there would not be much oil left in it. WRONG! Took almost a full bag of oil dry to clean up the mess so if you do this be sure to put down something to catch it all. See attached photo.
https://cimg1.ibsrv.net/gimg/www.mbw...8da28bedb5.jpg


Thanks to all who provided suggestions and guidance in getting this project done!

when you did your oil cooler seals, how did you get that turbo out? that heat cover has to come out I assume - any tips?

FYI, you can get both the oil filter housing seals on eBay for about $15 (they are sold as a set.) Also, if you don't trust eBay parts, you can replace the housing/block seal with a factory part and use high temperature RTV to make your own gasket for the internal filter housing seal.

Good update. I did the same job with an ebay gasket set last fall and have not had a problem since.

I bought those seals from Ebay for the filter housing and they leaked a week later. Ended up replacing the entire housing.

Could purple seals leak?
 

I’ve took my oil cooler off today and they already been replaced with purple seals.
Now question, could they leak after 80k miles?
my 350 has def deleted. Oil filter housing already replaced 6 months ago… can’t think of anything else.

Sadly could be one of a number of things. Likely valve cover leak (common at back passenger side). Any seal could leak. If yer already in - replace them. They are cheap. Oil leaves a trace. Inspect everything.