Oil in the Air Intake Manifold

[JJ 911SC]

I’m sucking oil into the AIM through the 90 degrees rubber boot/throttle body via the Main Vent.

The oil level is at half way, line has a restrictor at the oil thank side and the rev goes down when the oil cap is removed.

I tested the restrictor and I was able to have air flow through the hose both way. While there is a small hole on the restrictor (pointing toward the tank) I did not feel any more resistance going from the tank to the boot.

Also, not necessary related but could be, when I turn the car off, it give a long depressurizing gasp...

Thanks

JJ

[JJ 911SC]

Not really... Half way or below.

Maybe the restrict or is shut. I could not feel a pressure difference between one way (90 degree rubber boot to oil tank) or the reverse.

[86 911 Targa]

If your oil level is 1/2 full.

This may be what you need.



Or this.

[JJ 911SC]

Originally Posted by 86 911 Targa

... Or this.

I got this one in the hose but I think its shut...

[Steve@Rennsport]

I would recommend doing a leakdown test to eliminate any chance of a mechanical problem causing this issue.

If that checks out normal, I'd review your tank vent plumbing and dipstick calibration (assuming its always at the halfway level when the engine is HOT).

[JJ 911SC]

Steve

What would be the mechanical relationship?

More info (as usual)...

I had the engine out and every thing was clean when I put it back.

Unrelated, my VR when kaput 2 weeks later.

Since the damper bracket (Cabrio) would not let me do the easy swap, I end up removing the air intake, and access the back of the alternator after lifting the engine shroud (a real PITA, 5 hours to get there, 10 minutes to replace the VR and so on...)

I notice at that time that I had a line of oil coming down the Main Vent line on the 90 degrees boot. When I did a blow/suck on the line fitted with the restrict or, I did not notice any pressure change thus my leaning toward the restrict or being shut.

I triple check the vent pluming and never ran the tank above the mechanical half way point, with match the guage.

Cheers

JJ

[mytoy]

Yes, Steve, I also would like to know what mechanical problem could cause oil to go through the oil vent line into the air intake? I have the same problem and would like to know what to look for.

[Steve@Rennsport]

Gentlemen,

Mechanical issues that will push oil into the intake system through the vent line are broken rings and/or piston issues.

This allows cylinder pressure past the rings and pressurizes the engine case & oil tank.

Leakdown testing allows one to see if thats the case by noting leak percentages on the guage and noting where its coming from.

[JJ 911SC]

Originally Posted by Steve@Rennsport

Gentlemen,

Mechanical issues that will push oil into the intake system through the vent line are broken rings and/or piston issues.

This allows cylinder pressure past the rings and pressurizes the engine case & oil tank.

Leakdown testing allows one to see if thats the case by noting leak percentages on the guage and noting where its coming from.

Thanks.

In my case I got a very well define line dripping from the boot as oppose to splashing.

[T77911S]

Originally Posted by Steve@Rennsport

Gentlemen,

Mechanical issues that will push oil into the intake system through the vent line are broken rings and/or piston issues.

This allows cylinder pressure past the rings and pressurizes the engine case & oil tank.

Leakdown testing allows one to see if thats the case by noting leak percentages on the guage and noting where its coming from.

this along with just plain ol worn out rings, like my car has.

are you checking the oil level hot?

[JJ 911SC]

Originally Posted by T77911S

this along with just plain ol worn out rings, like my car has.

are you checking the oil level hot?

Yes, on level ground after a minute at idling. Half way on the stick and on the guage.

Its not coming from the engine as I can follow the oil trace from the back of the boot down the throttle assembly.

I'll be changing the in-hose restrictor as the air flow through the hose is the same either way.