Oil inside air filter housing

[DariusPri]

There's oil inside air filter housing (although oil level seems to be normal). Are there any other solutions apart from having entire engine rebuilt?

[gadget73]

make sure the line from the oil seperator on the valve cover to the oil pan is clear, and make sure the oil sep is not clogged up inside too.

[DariusPri]

Is it the tube marked in the picture as number 1?

[gadget73]

"1" is the oil separator. "9" is the drain tube. Both need to be clear. Also worth making sure 5 is not clogged up. Thats one of the oil drains for the head, and if it doesn't get the oil drained out properly you'll get extra oil in the separator.

[DariusPri]

So I took the oil separator off, got it clean and tubes too. Was a bit of doughy oily stuff inside, but not too much.
Maybe oil gets to the air filter housing from that big tube that goes to the turbo? (turbo itself I got checked a couple of weeks ago, and it had no issues)
I guess I'm out of simple fixes

[a]

When I bought my first 528e , Gas version of your diesel. It had 150 K miles on it. It leaked a qt of oil every 1.5K miles and condensed crankcase fumes in the air filter box, It was not performance affecting . I drove the car another 200 K miles. If your situation is not hurting performance, just keep ahead of consumption.
PS. I did switch to a cheap 20 w 50 oil as well.

[gadget73]

Mine gets a bit of oil through the breather tube, and it gets a little more out of the turbo seals. The turbo has no play but I get oil in the crossover pipe. I'm not going to worry about it, it runs fine and doesn't actually need oil between changes.