911 SC 83 white smoke like hell after hot. I am not James Bond

[HKZ Bob]

911 SC 83 white smoke like hell after hot. I am not James Bond


Dear All,
there is some strange behavior on my friends 911SC 83 which he is rebuilding.
After we were driving around, suddenly a huge cloud of white smokes comes out of the exhaust.
Some seconds later it is gone.
We checked the oil level on the running engine an reduced it to minimum level. We could not find the root cause yet. We smoked some bikers and than towed the car back.
Then we reduced the oil fill by 2 liters but the smoke still comes out in pushes like in a 007 movie. You canīt imagine how bad the white smoke is.


Any ID what could be the root cause of this problem?

BR
Bob

[tom1394racing]

Bob

If you overfilled it, you likely filled the muffler with oil that will take some driving to burn out completely.

[HKZ Bob]

Originally Posted by tom1394racing

Bob

If you overfilled it, you likely filled the muffler with oil that will take some driving to burn out completely.

That what we thought too,

but it comes not constantly at start. It starts when the engine is heated up.

BR
Bob

[tom1394racing]

Bob

It makes sense that the muffler will need to heat up before it starts burning off the oil.

Make sure the level in the tank stays constant while you smoke out muffler.

[JFairman]

I've seen a car that had a brake master cylinder that was leaking brake fluid into the brake booster which is hooked up to intake manifold vacuum.
The brakes really sucked on that car because the owner just kept adding brake fluid and the vacuum brake booster filled up with it so it wasn't working anymore.

The motor eventually started sucking brake fluid into the intake manifold and emitting weird smelling smoke from the exhaust.
It would take alot of brake fluid on a 911 to do that so it's probably not the problem on yours.

The most impressive smoke cloud from the exhaust I've seen is if you do a seafoam into a manifold vacuum line treatment at idle.
You can go to you tube and search "seafoam" and watch videos of kids doing that.

[HKZ Bob]

Originally Posted by JFairman

I've seen a car that had a brake master cylinder that was leaking brake fluid into the brake booster which is hooked up to intake manifold vacuum.
The brakes really sucked on that car because the owner just kept adding brake fluid and the vacuum brake booster filled up with it so it wasn't working anymore.

The motor eventually started sucking brake fluid into the intake manifold and emitting weird smelling smoke from the exhaust.
It would take alot of brake fluid on a 911 to do that so it's probably not the problem on yours.

The most impressive smoke cloud from the exhaust I've seen is if you do a seafoam into a manifold vacuum line treatment at idle.
You can go to you tube and search "seafoam" and watch videos of kids doing that.

That is an option with the brake master cylinder, if we exclude oil

Ouestion:
The smoke we have seen was fully white. How does oil smoke looks like ?
BR
Bob

[cstreit]

Oil expands when hot. Engine gets hot, oil expands and overflows.

There are only a few fluids in that car. Oil, washer, brake, and gas. Simpleest answer is oil. If it were gas, the car would burn down, brake fluid, he'd drive into a tree. Washer? I doubt it. Must be oil.

Check the oil level when hot and level.

[E Sully]

Is the restrictor in the oil tank vent tube? 930-107-289-00-M260

[john930]

If it has CIS, if the diaphrgam in the WUR ruptures doesnt the fuel exit into the aircleaner via a small pipe??

This could explain smoking only when it has warmed up?????

[boyt911sc]

Originally Posted by john930

If it has CIS, if the diaphrgam in the WUR ruptures doesnt the fuel exit into the aircleaner via a small pipe??

This could explain smoking only when it has warmed up?????

John,

Could you elaborate on your above statement? Are you talking about a CIS in a 911? I'm totally lost and couldn't follow the logic. Thanks.

Tony

[JFairman]

He said white smoke in the first post.
It it's blueish white thats oil burning.

Too much fuel would make black smoke, and if the WUR metering diaphram ruptured then hydraulic control pressure would drop from the control pressure fuel leak letting the control plunger raise higher in it's cylinder uncovering more of the fuel metering slits and the motor would go wayyy rich.

Add the fuel going into the air cleaner housing from the WUR vent hose and it would probably become so rich it would hardly run while misfiring and pumping out black smoke.

[Henry Schmidt]

83 911 SC engines are high compression lean burn engines.
It is not uncommon for these engines to detonate and break a piston.
Seen too many to count.

[HKZ Bob]

Originally Posted by E Sully

Is the restrictor in the oil tank vent tube? 930-107-289-00-M260

What is the restrictor in the oil tank doing and where is the location?

BR
bob

[Flat6pac]

Its located in the oil line from the tank to the throttle body. If it s not installed there is a tenancy for the engine to stumble to stall when the oil cap is removed. If its there the engine stumbles some when you read the dipstick because of unmeasured air into the throttle body.
Bruce

[E Sully]

The restrictor limits the amount of air flow from the oil tank to the intake, but I believe it would also help prevent oil from the tank from reaching the throttle body.

[HKZ Bob]

Originally Posted by Flat6pac

Its located in the oil line from the tank to the throttle body. If it s not installed there is a tenancy for the engine to stumble to stall when the oil cap is removed. If its there the engine stumbles some when you read the dipstick because of unmeasured air into the throttle body.
Bruce

Thank you Bruce & Sully.
The engine does not stumble when you remove the oil cap.

I could read the oil fill at idle with no probem.

BR
Bob

[Kemo]

does the smoke come consistently after hot or only during a deceleration event? like running your engine up to 6K then letting the engine drag down the speed.

I have heard that could indicate that the heads need to be looked at. Hopefully somebody here with more experience can confirm or deny this.

[James Brown]

Take the valve covers off and look for a shifted rocker shaft. If they do that, oil will dump right into the heat exchangers making, well, white smoke! Any oil or wet stuff inside the exhaust pipe?

[t2002v]

Gents: I also feel like James Bond!

Details: 1981 911 SC, 36,000 miles-engine always runs great and smog's easily within the confines of Calif rules.
I don't drive the vehicle very often and I let it sit for approx 3-4 wks, upon starting which took a few cranks the engine fired and drove just fine. I was smoking out the place, I stopped the car and pushed it back to my garage. Since then I have re-started the car, it pushes "White" smoke from light off, clears after approx 30secs and then proceeds to billow a smoke screen. I have not been brave enough to run it for any period of time, no clatter, revs great and other than the "White" smoke, operating like usual. The oil level was perfect-no overfill issues. I thought this issue was a function of either the Aux Air Valve/Aux Air Regulator, someone know if one of these are malfunctioning and producing the "White" smoke? Note: the smoke has 0 order and is pure white...no blue tint and does not smell or look like oil is being combusted in the cyl's. Thanks...sorry for the long post!

[nikke911]

I had this issue on my -79 SC. The engine collected oil in the crankcase and smoked like hell.Iīve since read about this matter in some book or magazine,and it had something to do with the oil pick-up tube missing the mesh-sump which was added later.Can not remember exactly what the teory was why it collected oil,but this could be the problem..