bhpplease

Hi Guys,

So I bought my S212 E350 CGI in January this year - discovering a leak on post purchase inspection. (The car has 192k miles on it).

In the summer I serviced the car, changing the oil - since then I have put 1500 miles and last week I got a note to check the oil at next refuel. Oil level is now at min point.

I want to fix this leak because the engine is very oily and a ***** to work on and well... a leak must simply just be fixed! At this point in time, I can't figure out the leak location because the entire block and all parts seem oily.. even the sump cover exterior was covered in oil when changing in summer.

So the main point of this forum is to get some guidance on the diagnostic process and finding the leak, which is the only way to really fix it.

My process shall be along the lines of:

1. Give the engine (+ sump exterior + under trays) a good thorough clean
2. Drive the car a bit (nice and spirited).
3. Observe for oil leaks
4. Replace parts that appear to be leaking

Parts known to leak:

1. Oil filler cap + seal
2. Camshaft magnet/solenoid
3. Expansion plugs (cam caps)
4. Oil breather
5. Oil separator
6. Relating breather / separator pipes
7. Oil cooler and filter associated seal
8. Rocker/Valve/Cam cover gasket (one per cylinder bank)

Some related questions I have:

1. Is there a gasket in the lower sump housing? I couldn't seem to find in WIS.
2. The sound proofing/insulation in the engine cover/air filter box has been sopping wet with oil. I have since cleaned it. It would lead me to believe that the leak is the engine breather box (photo attached) Would a leaking breather box be enough to soak the entire sound proofing?
3. My hunch is that over time, given capillary action, the oil could be sucked all through the sound proofing, and the heat could promote dripping of the oil all over the engine.
4. I could wedge a sponge between the breather box and engine cover to see if much oil comes from there after some miles - good/bad idea?
5. I'm not sure if the amount of oil lost in the leak could have all come out this way to be honest. I noticed during oil service the underbody cover was oily.. I haven't replaced after service, but this could also help me detect if the leak is from the sump.

Next steps

1. Thoroughly clean engine block
2. Clean engine oil sump under car
3. Clean engine cover
4. Clean underbody covers and replace to cars

Spazm.Xylam

A part to add for the known leaks would be the cam caps on the back side of the heads. (obviously not the source for the front side mess, but worth looking at while you are hunting down some leaks.) There are 3 plain round caps and then one box looking thing. Mercedes calls it a centrifuge and it is cam driven.

As far as lower sump gasket, no there is not. RTV seals many of the engine segments. (Oil sump, front cover, front cam covers, etc.) I would recommend the gray Permatex stuff. Looks like 82194 is permatex's part #

The components (oil cooler, oil seperator, etc.) will have o-ring/gasket type seals.

Otherwise i would say your diagnostic plan outline is a good one. Clean it up good and look for the wet spot.

bhpplease

Thanks for that - I had mentioned those parts as the "expansion plugs" above, but I have amended that point. But thank you for highlighting. I am not sure if they are still an issue as I saw a tech bulletin saying it was an issue up to 2008. That said, if warranted, I will replace. They cost very little to purchase, anyway.

I've just been around the carwash and attempted to clean the underbody covers.. they are totally caked with oil and require mechanical cleaning/steam cleaning which wasn't totally possible. I think they are in a bit of a better state and I hopefully will be able to identify any fresh oil in those areas. Later, I will get under the car, clean the sump and replace the covers.

Question: Does anybody have any opinion on leak detection solutions such as spray or UV ink that is added to the oil? I am high tech guy and like the idea of UV, but only if it works well.

Pics of underbody covers... i'm not sure how many miles of oil leaks are caked on here..

Spazm.Xylam

For UV detection, you can get little additive bottles from just about any parts store (here in the US anyway, i dont see why not elsewhere.) I have had mixed results using it though.

bhpplease

OK guys, a quick update..

I think I have isolated the leak in the engine to the "oil separator box", as shown in first pic of first post. I will be buying that. Along with the hoses and the separator that goes at the back of the engine.. Happy to do those as they are known issues.

Also... I replaced the pans under the car and cleaned up the oil sump. The sump was pretty covered in oil (pics below), which I cleaned off with brake cleaner and a cloth. It's now much cleaner so I can inspect again in a few hundred miles to see if there if the oil returns. From looking at it.. it looks like the gasket may be leaking..if you observe the collections of oil around the screws etc. And it seems to be one side of the sump only. Perhaps a new gasket is needed.

On the other hand...a second theory could be that the oil from the breather box up top (or whatever the leak is) is being sucked up into the engine cover housing foam (capillary action) then when heated by the engine drips down onto the engine...and eventually running all the way to the sump, which is the lowest point. I don't know if there is a route that would allow that. Is that possible or much more likely to have two leaks?

P.S. FWIW - The sump looked like that before I changed oil in June. I also used a new washer and torqued the drain plug to spec... even thought the slight collection/drop of oil under the drain plug looks a bit suspect. I highly doubt the drain is leaking.