Sci-fi_Wasabi

I had an oil change done on my 09 A8L at an independent mechanic, and 3 days later noted a puddle of oil on the ground. I took it back and they said that the oil pan drain bolt is fine with no signs of leakage, so it was not that it was not on tight. They did note that the OIL SEPARATOR had a crack in, and did not find any source of a leak big enough to make a puddle after putting dye in the oil and idling it. They said that the OIL Separator commonly fails as it is a plastic piece, but i have not seen this on the forum here.
I was just wondering if a crack in the OIL SEPARATOR would actually produce enough of an oil leak to make a puddle on the ground, looked like more than 1/2 a cup maybe. I don't think that oil actively flows through it, i thought it just keeps oil and air from intermingling in the manifold.
The oil was at the full level after the change so maybe this exacerbates things and more pours out or something.
Just wanted some thought from others as to if a crack in the housing of this part could produce that much oil and if oil actively flows through it, before the $660 repair.
Thanks

mishar

What year is your A8?

Sci-fi_Wasabi

It is a 2009 A8L 4.2 L FSI engine (sorry should have mentioned engine type), thanks

mishar

Cracked oil separator and oil overfill might cause some oil leak, but as oil separator is on top of your engine, close to the windshield everything would be oily before you get that much oil on the floor.

Mister Bally

Mishar, you meant to type OIL SEPARATOR.

Sci-fi_Wasabi

Thanks Mishar,
I did not mean to yell with the caps, I was merely highlighting the subject of the topic for those who skim posts in the future on oil leaks. Hopefully that is the only source of the leak.

MP4.2+6.0

and that is having owned a 2000 A6 4.2 that had oil issues over the years. On that motor, I think of the first level oil separator as being down in the valley under the gasketed, bolted down metal cover and under the intake manifold--as in, no way oil was getting out of there. Then there was the Y suction valve--aka suck valve which is still on my W12 in a T shape instead of a Y--which when it failed badly could suck oil into the motor and out the exhaust big time. And finally, the world's most expensive ridiculously over engineered PCV valve, which i guess is still on the D3 4.2's but went away on my W12 in favor of some twinned components.

Anyway, I don't have a D3 4.2, but am at bit of a loss wondering what this is about; the principal thing I used to see that physically was prone to leaking oil was the usual valve cover gasket suspect, typically toward a back corner.

mishar

OIL SEPARATOR is #5. So, again, if 1/2 cup of oil is on the floor there would be another two cups all over the engine.

Sci-fi_Wasabi

Yep that's it Mishar, I've seen some websites call it a breather valve and some just refer to it as the PCV valve...
I did ask to drive my car to give the dye some more time to work its way through while under real life conditions, since they saw no other leaks. I do see oil right where number #7 oil return pipe goes in to the #5 OIL SEPARATOR, and on the engine directly below. I'm not sure if that explains the larger loss of oil, nor do i see any upwards splash on to the windshield or underside of the hood. Perhaps pressure on it did increase with slight overfill of oil or something.
I'm contemplating doing this myself, but seem that I need to remove the throttle body, which is not bad, but those #15 hose clamps are some kind of single use pinch clamps that get crimped. Not sure if I can remove it in such a tight space, nor am I sure if i can replace it in such a tight space. Overall very limited space to ratchet.

EHLO

More specifically it's the Fine Oil Separator (5), and my S8 has one in the same location.
The function is to separate vaporized oil out of the crankcase from the tube (1) between the cylinder heads, before the mix gets sucked into the intake manifold.
Doing so reduces intake valve carbon buildup.
It's unlikely that that much oil would flow out of a crack in that amount of time, even if the return valve (7) to the crankcase was stuck shut.
I had a pinhole leak in the tube, and it slowly coated the right cylinder head with oil.