Hi I have a 2012 E350 Bluetec with the OM642 Bluetec that I bought with about 115,000 miles in August. Shortly after I bought the car it started leaking oil from everywhere and I found out the timing chain was stretched. I hired an independent mechanic to replace the timing chain and he attempted to repair a lot of the leaks. He said most of the leak was coming from the power steering pump so he installed a rebuilt pump and new hose. I spent two weeks at the end of December tearing everything apart to replace the oil cooler seals. It was still leaking badly and so far I've replaced the diaphragm in the CCV (mechanic already replaced the shaft seal), oil filter housing and gasket (fixed a large leak on top of the alternator), oil filler cap, vacuum pump (used black RTV on the gasket because the head to valve cover joint isn't quite flush it leaked there when the mechanic installed it dry, I also installed a new o-ring seems dry now), replaced all the seals in the black plastic intake pipe from the intercooler hose to the intake manifold, replaced all the o-ring seals in the turbo to silencer pipe and intercooler hoses. The bottom of the alternator, rack and pinion, and some transmission lines have oil puddling on them. If I dry everything off and watch it for a few minutes I don't see any leaks. If I take it for a good 20-30 minute drive on the freeway I can see the passenger side of the rack get oily and it leaks about a spot of oil on the passenger front directly under the vacuum pump/oil filler cap/timing chain tensioner area everyday. The front mid-cover belly pan is missing. The mechanic did install a new timing chain tensioner which appears dry. I passenger rubber intercooler hose and connections appear dry. I suppose it could be residual oil from inside the alternator, but it's been about a week/200 miles since I resealed the vacuum pump, so I thought it would be dry by now. Any ideas what to replace next?

 

Tracing small oil leaks can be a nightmare, so try to be patient. I keep my engines clean, so each time leak develops, I can see it right away and wrapping the area with paper towels helps to pinpoint the location.
That said on my last OM642 I had oil filter housing leak, what was dripping on belt and splashing oil all around Took some time to pinpoint that one.
The housing has 2 unique seals on it.

 

Thanks kajtek1. I didn't want to take any risks and put in a new oil filter housing. The driver's side has been dry since. Paper towels sounds like a good idea.

 

did you change the entire housing or just the seals? Mine looks like it’s leaking. Also looks like the black box where the turbo inlet attaches too is leaking too

 

I replaced seals only. It was about 4 years ago and finding the center seal was quite a task, but lately I have seen some suppliers selling both seals in a kit.

 

I replaced the entire housing. I didn't know the seal in the center was available. Check IDParts.com. I had to replace the entire clean air duct. The old one snapped when I tried to put a new seal in it. Super brittle.

 

Not sure if the same but on my OM648, the oil line to the turbo is leaking since the o-ring is dried out (engine block side). This is difficult to change since it is rigid line and need to align properly otherwise the new o-ring will get cut.

 

Oil cooler sounds like a reasonable bet. If you said driver's side leak I would say check the oil cooler pedestal, just did that. Kind of a pain but nothing like the oil cooler.