It is a 2008 535i. It has 80k miles so far.

This has been couple months already. Recently, it got worse. I found that there is always some dirty oil building up under the engine oil filter cap. Just last weekend, after sitting in the cold weather for five days, when I started the car, the front fan started to work toward the cold engine, then it kept working all the way after I drove 30 miles. Then I found a large amount of oil near the filter and the air hose close to the filter.

Is this really an engine oil leak, or might be coolant leak? The facts: I just got water pump and thermostat replaced eight months ago, engine oil changed four months ago. The engine level shown on iDrive is okay, a little bit lower than right after oil change.

Is this common? What should I do to it? I did see some oil got in the coil below. Is it very dangerous? I wonder if the oil got in the coil messed up the fan switch...

Thank you very much for any information! On weekend, I will try to take more pics. It looks really messy from the bottom.

 

Definitely oil. Maybe the o-ring on the oil filter housing is cracked/missing...

 

Thanks. Can I change the o-rings myself?

 

My guess from looking at the third pic is its either gasket number #4 or #5 in the link. The part isn't listed but I know the filter comes with an O-ring...

It doesn't look too difficult just messy.

http://www.realoem.com/bmw/showparts...71&hg=11&fg=30

 

Thanks for the database! It seems to have everything. But I still have difficulties locate the required gaskets. In the 3rd picture, the two hose are come the part 9 in your link, (http://www.realoem.com/bmw/showparts...g=30&lang=enUS). Is part 9 the thermostat? What are the two hose called?

I did get the thermostat replaced recently, (if that part is thermostat) maybe the leaking is caused by the replacement?

 

i had a leak like that in picture #3 and it turned out to be oil filter housing gasket

part number 5 on the above link ^^^

 

Here are the what the hoses are called.
http://www.realoem.com/bmw/showparts...g=05&lang=enUS

My guess is that you had these two cooling system components replaced since its more common. They are located on the passenger side near the bottom of the engine. At least on my N52 engine they are.
http://www.realoem.com/bmw/showparts...l=16&lang=enUS

I doubt they replaced part #9, the thermostat housing, but if they did maybe they'll fix it. To get to those gaskets you'd have to remove part #9.

 

Got one more picture:

It seems that there are leaking on all the joint of the three hoses in front of the engine....are they just wear-out or what?

 

Aren't those oil coolers hoses? I believe only coolant runs through those hoses not oil.
Maybe some of the oil from the top leak got on them...
If the joints are leaking whatever they have in, oil/coolant, them my guess the only repair would be to swap out the hoses completely.

 

I would clean the entire area with brake parts cleaner and keep an eye... for source of the leak.

My guess is that the oil leaked from oil filter housing gasket is causing all of that mess.