Crankcase filling with oil

[rbutts]

I have a 79 911sc that puffs a lot of oil every time I start it, and it is oil. When I drain the oil there is more oil in the case than there is in the oil bag. So I did an experiment by draining one to two quarts of oil out of the crank case then starting it and to my amazement absolutely no smoke on start up. I've repeated this three times and no smoke . Also let the car sit and not bleed off oil and start it and it puffs quite a bit of oil each time and eventually clears up.Is there any way to fix this with out tearing down the engine and rebuilding the oil pumps.

Thanx in advance
Rob Butler

[4sd911]

Do you have the updated oil sump screen?
http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=930-107-314-00-M253&catalog_description=Engine%20Oil%20Sump%20Screen%2 C%20%39%31%31%20%28%31%39%36%35%2D%38%33%29%2C%20% 39%31%31%20Turbo%20%28%31%39%37%36%2D%37%37%29%20

[rbutts]

Yes I have the updated oil screen. I also have carbs so my oil tank has a filter/breather on it instead of routing breather back to the carbs. It started to over fill the case with oil after carb installation and having an open breather. Seems odd ?
Rbutts

[Flat6pac]

Run low on your dipstick, the oil will balance between the tank and the engine when you set for the night. The level will be above the exhaust valve from sitting. If you run a quart or 2 low, you wont soak the exhaust valves any more.
Bruce

[john walker's workshop]

has the engine been apart? if one of the big red o-rings on the oil pump was displaced, they don't scavenge well.

[Eagledriver]

Does the oil drain from the tank when the car sits or is the oil not scavenging from the bottom of the engine while it's running. If it's draining when the car sits (oil level drops in tank over time), then that is normal (or at least common) and I wouldn't worry about it. If the engine is not scavenging then you have a problem you need to address. Symptoms of lack of scavenging include: overheating, smoking, and loss of power. Some SC's had this problem but it seemed to only show up on the track.

-Andy

[ischmitz]

Rob,

It would be interesting to check how much if any oil you can drain out of the engine sump right after you shut it down.

My guess is that your pump is scavenging properly but oil creeps through the scavenge line back into the engine sump when the car sits over night. If that is the case you'd have to pull the oil pump and that is a complete engine case split. As others said, as long as the pump scacenges fine I wouldn't worry about it. Look on the bright side: It's a good indicator you still have enough oil. When it stops smoking during startup you know you are low.....

Ingo

[TVRLOTUSTR3]

My 2.4 also puffs a bit at start-up. I blame it on the Deeves rings that I used in the rebuild.

What does this oil screen update do to help this?

[ahdoman]

My 77 2.7CIS does this as well. What causes the oil to drain from the tank when it sits? Is that a repair that needs to be done at the oil pump? If so, what?

[rbutts]

Thanks for all the replies. Here's whast I've concluded after a few more experiments I noticed more oil smoke on start up after the new Pmo carbs were installed.If I rev the engine a little bit on start up it starts billowing oil.If when I start it ,I keep the revs bellow 1000rpm no oil smoke.I let it run for about a minute ,rev it up no smoke. My conclusion is that the excess oil in the case scavenges out better at idle, thus let it idle at start up.

Rbutts

[Bob Goding]

I know that better minds than mine will hasten to correct me if i'm wrong --but heres is my take on this problem. The scavenge pump returns the case oil to the oiltank,and feeds it in at the top of the tank. Therefore the only oil that can run back thru the scavenge pump is whatever is in the line--above the pump --certainly not 2 quarts----but the pressure pump gets its supply from the bottom of the tank along that fat s-pipe that goes into the engine thru the pipe under the cooler.
Thus the pressure pump has the head of oil in the tank when the engine is stopped.
So the oil gets into the case thru the pressure pump? How about a shutoff valve in that fat hose-operated by the ignition key. Hate to think of the consequences when the valve malfunctions due to a stone hit or something!--But just think Airbus!

[Eagledriver]

While Bob's solution certainly should work, it is solving a problem that doesn't need to be solved. My oil tank drains almost completly into the engine if the car sits for more than a few days. Once started the scavenge pump returns the oil to the tank in about 10 seconds or so. While there is a lack of oil pressure for a few seconds after starting, I don't feel this is a problem.

-Andy

[T77911S]

Originally Posted by john walker's workshop

has the engine been apart? if one of the big red o-rings on the oil pump was displaced, they don't scavenge well.

mine has done this ever since i bought it, more than 5 years ago. i always assumed it was normal for the oil to drain back into the engine when it sits. i figured the oil either seeped past the rings or the valve stem seals, which is why when he drained the oil, it was not high enough in the case to do this.

when my car is cold, the oil level gage( i have checked mine and it is consistant with the level in the tank) reads in the red, but when warm and idling, it shows the correct level. but, if i rev the motor, the oil level goes low in the oil tank.
i always thought this was becuase porsche made the scavange side smaller and the pressure side of the oil pump bigger.

[P911sjp]

HI just had exactly this happen on a newly rebuilt engine with all new and expensive parts.
The engine is ok from cold but then there is a build up of smoke. Its a mechanical injector model 2.4E. (pressure is fine).
We've completely restripped the engine and cannot find anything else wrong can't be valve seals as its occurring on all cylinders. Seems to be flooding from underneath. Suggestions on the scavenging side is all that seems to be coming up but as the engine is all apart is there a solution?
We're checking all pipes for blockages at the moment. There are some pipes within the tank itself so maybe thats where it is.!

[matt demaria]

A couple of items here.
First it is normal for the engine oil level to rise after a period of time. The oil tank and the engine sump will seek the same level. When the engine sump level rises it usually will rise above the level of the exhaust guide seals and seep into the ports and lay in the bottom of the heat exchanger. If the guides are worn the seals will usually leak oil faster into the heater box. This causes a lot of oil smoke in the starting mode. A quick check for this is to jack up one side of the car so the car is leaning over about 5 degrees. After an hour start the car to see how much oil comes out the exhaust.
The second problem here is that the PMO's are porous. They usually will drain the bowls overnight into the intake ports and then into the cylinders. Eventually this will dilute the oil supply. So make sure you aren't misdiagnosing a brief overrich condition from the PMO's.

[rcaradimos]

Originally Posted by rbutts

I have a 79 911sc that puffs a lot of oil every time I start it, and it is oil. When I drain the oil there is more oil in the case than there is in the oil bag. So I did an experiment by draining one to two quarts of oil out of the crank case then starting it and to my amazement absolutely no smoke on start up. I've repeated this three times and no smoke . Also let the car sit and not bleed off oil and start it and it puffs quite a bit of oil each time and eventually clears up.Is there any way to fix this with out tearing down the engine and rebuilding the oil pumps.

Thanx in advance
Rob Butler

Did you find the fix? Was it valve stem seals on the exhaust, oil seeping in the exhaust manifolds when the crank fills up with oil?