Oil in Air fliter housing??

vichang4 · 12-01-2004, 06:19 PM

I read a recent post about oil collecting in the air filter housing and leaking out on/around the engine.
I have an 87 911 turbo that I just rebuilt the engine on. Full rebuild, reconditioned RUF 3.4 L pistons and cylinders, full head work. The engine runs great and had no leaks untill I took it to a DE. At the end of the first session I noticed a leak on the front right side of the engine near the oil cooler. I traced the leak to the air cleaner housing! There was a pool of oil inside of the housing upstream of the air cleaner. See arrow on photo.

The oil level in the tank was below the halfway mark on the dipstick.

How is this oil getting in the air filter housing?
Could this be a result of valve or piston blow by?
What should I check?

I'm going to do a compression and leakdown test as soon as possible. I've been driving the car on the street without any problems??
Thanks for any help.
Victor Toce

relkceb · 12-01-2004, 06:52 PM

The reason their is oil in the filter housing is probably becasue before the driving school the oil level was to high. At the driving school your car gets alot hotter than it ever would on the street. The oil filler vents into the air filter housing, so if the oil level is to high the pressure forces it out into the air filter housing. I had this problem once before. To check your oil level make sure the car is nice and hot the temp guage should be around half way. When you check the oil level the oil should just barely show on the stick. This is what I was told by a club racer and I have never had a problem since.

relkceb · 12-01-2004, 07:00 PM

Hey Victor what color blue is your car?

cowtown · 07:03 PM

I had exactly the same problem with my '77 930 engine on the track (only).

Have you seen my thread: Turbo vent is dumping oil into the airbox (on the track only)

I believe this to be a problem with the Turbo engines only. The vent for the turbo oil collection tank is plumbed into the air intake. On the track, one of two things happens:
1) A lot of vacuum in the airbox pulls oil up from the turbo's oil collection tank into the intake
2) The high revs and oil pressures on the track cause the turbo oil tank to fill all the way up and overwhelm the scavenge pump. The oil has nowhere to go but up into the airbox.

I solved this problem by installing a Moroso oil catch tank on my 930 engine and getting rid of the stock airbox. The turbo's oil collection tank vent is plumbed back into the oil tank, and the catch tank gets all the vapor and overflow.

vichang4 · 12-01-2004, 07:04 PM

I never had this problem before the rebuild? When I first found the oil I checked the oil level while the engine was HOT, 120 C . It was approximately 1/3 up from the bottom mark on the dipstick. I have run higher oil levels at previous DE's, before the rebuild, without the oil problem??

Could anything else be causing this problem?

The engine does run a little hotter so this would cause more expansion?? Also, I installed 22mm and 30mm torsion bars, so the car is running quicker lap times, more G forces??

mede8er · mede8er's Garage

I'd say more/better vacuum after the rebuild......

vichang4 · 12-01-2004, 07:42 PM

Quote:

Originally posted by hobieboy

A couple of thoughts...
a) Make sure that you have that little ball (4mm I think) in the oil pressure switch where the turbo oil supply line is hooked up to. This ball is used to limit amount of oil going into the turbo.

My car is an 87 911 turbo. Does it have this ball ??
I don't remember it. The factory manual has a nice diagram of the switch and ball, but it states "for turbocharger with oil pressure switch". Do just the pre 79 cars have this? I need to do a little detective work on my car.

vichang4 · 12-01-2004, 07:50 PM

Quote:

Originally posted by cowtown

2) The high revs and oil pressures on the track cause the turbo oil tank to fill all the way up and overwhelm the scavenge pump. The oil has nowhere to go but up into the airbox.

One more thought. I installed the modified oil fittings on the oil lines near the valve covers that Wayne reccomends in his rebuild book. This has raised the oil pressure in other parts of the engine including the oil going to the turbo. Maybe this "fix" is causing too much oil to the turbo.

PSRacing · 12-01-2004, 08:01 PM

Yes you must use the ball under the oil pressure switch to control the volume, the part number is 900 108 022 00. The other things to check are the engine breather hoses. Make sure that none of them have been kinked or are pinched off. Also check the oil return line from the turbo to the tank. Did you change your exhaust to headers; I have had problems with the aftermarket turbo reservoir being too small.

Doug