Turbo - Oil in airbox. Need help!

I'm having a VERY annoying problem with my 930. When I'm out on the track, I am getting QUARTS of oil being blown into my airbox throught the oil resevoir breather tube. The tube does appear to have a return line with some sort of collector on it back to the bottom of the resevoir, but apparently it doesn't work. I've run the car 2-3 quarts low and I STILL get this. I checked the leak-down and compression thinking a broken ring was over-pressurizing the crankcase, but they show fine.
Is there an update or solution to this? I set up a resevoir for the breather to dump into, but I am still losing oil into that instead of returning to the main oil resevoir.

Please help! Thanks

Whew!!! Took a bit of detective work looking at your previous post about your low oil pressure problem! Does it still have lower than spec oil pressure at 5000 rpm? I think you have much more SERIOUS PROBLEM than an 'annoying' problem on your hands!!! And, I am very certain the problem IS DIRECTLY related to the pressure relief valves, because your engine has the 'mod' described by Bruce Anderson as the 'bypass circuit mod' !!! If a spring is weak, or if a valve gets stuck or 'cocked' in its' bore you have essentially a continuous loop from the outlet of the pressure pump around to the inlet of the pressure pump ... hence, LOW OIL PRESSURE, AND less oil being used from the tank, though the scavenge pump is working normally, keeping the sump mostly 'dry' ... so your tank is pushing the excess scavenge oil into your airbox!!!

I strongly suggest you stop driving your car IMMEDIATELY, and disassemble both pressure relief valves and springs, and purchase new springs and valve plungers! You have been STARVING that engine of it's oil supply, for how long? I suspect rod bearing damage already has been done, and maybe other valve gear problems as well!

Email Bruce Anderson for a confirmation, if you wish, but there is NO other explanation possible!!!

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Warren Hall
1973 911S Targa

EXCUSE ME, but you were told what the problem was on February 6!!! Those springs are supposed to measure 70.0 mm, and nothing less is acceptable!

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Warren Hall
1973 911S Targa

If I didn't know better, I'd think I was about to be sent to the principals office! *grin*

For some reason, I was not notified of your response Warren. However....

Several months ago, I did replace both of the pressure relief valves in the system... The pressure is still a tad low (perhaps 10% off factory spec) but I would assume this is from normal wear (in 18 years ) of the rod bearings. What do you think? It had not occured to me that both problems might be related, but I whacked myself on the head after reading your response, makes a lot of sense.

I haven't been out on the track since this happened, but presumably with the new springs in the car (since, ohh, december) I shouldn't have this problem?!

Thanks for the insight. I was a bit more panicked the first time because I was given the Carrera oil pressure spec first by a dealer (oops) which is a bit higher than the Turbo. Turns out that I'm not that far off.

Thanks again for doing the legwork on my previous response. I REALLY appreciate it. (So will the oil-dry guy at the track)

Chris

BTW, I was told by the factory manuals that the thermostat could not really be re-built and should not be disasembled, so I replaced it at that time. Gave my oil-coolers a good clean and flush too.

The car has been in the paint shop since January though, so no time to test all these fixes yet.

Thanks again.

Chris

Warren,

I talked with Andial and my mechanic and they weren't so sure that this is really my problem. Here's why:

Let's assume that there is 10 quarts of oil in the whole system when I'm on the track. (Porsche recommended running at the bottom of the dipstick range) The resevoir itself should hold at least 8 (conservatively). The various oil coolers and lines running to the front will hold at least two more. Since I have always had OK oil pressure, there must also be some in the pressure pump side of the system.

If there are 10 quarts of oil in the system, and two are in the coolers, 1 in the pressure side, that only leaves 7 quarts to be held in the resevoir. THis does not seem enough to blow 2 quarts into the airbox simply by overfilling of the resevoir... (It would have to be full because the vent is at the TOP of the filler neck).

Make sense? (THis is ignoring the g-forces of hard left turns of course)

Chris

I am going to have to say I don't quite understand the thinking of your mechanic or Andial contact, either! And, I am going to point out a typographical error in Bruce Anderson's 'Handbook' that happened between the 2st and 2nd editions and a slight 'oversight' that occured not 'tying together' all of the aspects of the 'oil bypass mod'!!!

On p. 58 of the 2nd ed. 'Handbook' is an 'engine oiling diagram' that was labeled with the text of the label from the p.57 diagram, but it contains an 'omission' in that it SHOULD have had added: 'for all engines up to the 1976 bypass mod'! There is NO diagram depicting the post-bypass mod engines in either ed. of the 'Handbook'!!! I am going to scan that diagram later, and attempt to 'edit' it with PhotoShop to 'add' the bypass mod and its' importance to your oil-airbox problem.

Is there ANY possibility the 'early-type' plunger shown on the right side of the photograph on p. 63 of the 2nd ed. 'Handbook' was inadvertently placed in the pressure relief valve position on the right crankcase-half vertical plunger location? Has your car always had the 'slightly low' oil pressure readings since you owned it, or is this a recent, NEW phenomenon? Also, is there some question as to the correct quantity of oil to be put back in the engine after an oil change? My recollection is that all cars with external, front fender coolers had a capacity of 13 liters of oil, from the 1974 spec. book. By my calculator, that works out to 13.74 qts of oil! Are you telling us that you have been running with 10 or 11 qts of oil in the system and the airbox STILL ends up with 1 or 2 qts of oil in it?

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Warren Hall
1973 911S Targa

I seem to have the first edition, as my page numbers and diagrams do not match up. The plungers I received were identical for both the vertical and horizontally mounted positions. They also were identical in style to the old ones I removed. The pistons DO NOT have the holes in them, they have the inscribed ring. I think this is what you mean?

The car always had low oil pressure. The new springs did bring it up slightly, but not enough to even say it wasn't "wishful thinking". I am running 7psi lower than factory spec.

As far as oil levels go. I usually add 8-9 quarts after an oil change, let the car get to operating temp, then continue to add untill it shows about the upper 1/3 on the hi-low marks on the dipstick. Usually this is around 11-12 quarts or so. (I THINK, it's been a few months.)

I think I need to gain bend my mind around the whole system for a while, as you are at just about the far reaches of my knowledge as yet.

Interestingly, Dieter (the DI in Andial) suggested that it might have something to do with the oil separator. A piece that I have yet to find in a diagrams.

Well, there is no doubt that Dieter has a lot more experience with these engines than I do, and he doesn't suffer from the lack of documentation us 'regular' owner/mechanics do. I just have to believe there is a 'simple' explanation, rather than a 'complex' one, though I am beginning to wonder about 18-year old seals for the oil pumps, say the pressure outlet on its' way to the thermostat and engine-mounted cooler???

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Warren Hall
1973 911S Targa

Agreed. Most likely candidate, no matter the mechanics of it, is some sort of overpressurization of the crankcase. We also speculated on worn or possibly a broken ring, but a compression and leakdown test really didn't lend any clues, they were within reasonable parameters...

I'm probably going to do a complete "down to the bottom" rebuild next year anyway, so if I can make it through this years track days and trips it will be enough. If not, well, we'll have our answer sooner

I really don't know what else it could be, but maybe you could put in an 'auxillary catch tank' of at least 1 gal. capacity, located as high as possible under the fender, with a 'drain' line back into the main oil tank at the same point as the oil filler neck, an inlet from the 'breather' hose that would normally go to the airbox at the 'mid' level of the 'new auxillary tank, and a vent at its' highest point back to the airbox.

On a lighter note, your engine is beginning to sound like a variation on the classic 'perpetual motion machine' ... except in this case, it is a 'perpetual petroleum factory' that turns 9 qts. of oil into 12 or 13 in all the wrong places!!! I am hoping 'we' find out what is happening before it makes any 'expensive' noises at the track!

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Warren Hall
1973 911S Targa