Oil coming out of crank case vent?

[Erik Dettloff]

I have a 1970 911T with K&N air filters. So I have the crank case vent hose running straight out with a little K&N filter on the end of the hose. The other day I ran the car pretty hard (high rpm's) and when I got home I noticed that the vent had (was) leaking oil. Why would oil come out of the vent? Is this from excessive crank case pressure? Thanks for your advice.
Erik

[GIBSON]

Erik
High rpms combined with oil levels on the full side can allow oil to use the built-in escape method, the breather system. Porsche included it just for drives like you had the other day.
While you can't rule out something else causing excessive crankcase pressure, it's likely you just got some normal overflow from the tank caused by the higher rpms and high oil level.
If you don't normally have the problem at lower rpms I doubt it's a problem. I would worry if I suddenly noticed higher oil pressures and or oil out the breather without the above circumstances.

[911pcars]

Our engines will blow out a small amount of blowby and oil mist. On a stock engine, this goes to the air filter housing where it's recirculated back into the engine. With any aftermarket air filter setup with MFI or Webers, I'd suggest installing a catch tank to collect whatever oil happens to be pushed out before venting back to the engine (preferred) or to atmosphere (2nd choice).

If this is something that suddenly happened (all else being the same), I might suspect additional blowby which increases pressure in the crankcase/oil tank.

Hopefully it's just a case of the oil level being too correct as Gibson pointed out. For peace of mind, you could do a compression test and compare with your last set of readings.

Sherwood Lee
http://members.rennlist.org/911pcars
www.seinesystems.com

[Erik Dettloff]

Thanks guys. It did just happen and normally dosn't and has stopped since. I'll do a compression test to check things out, but I think I'll be ok. Thanks again.
Erik