Blue oil smoke at start up

[avorkinn]

If I shut off the engine when it's cold (e.g. just take it out of the garage) and leave it for some time, next time I starts it a big cloud of blue oil smoke appear from the exaustpipe.
If the engine is hot at shutdown no smoke at all at next start up, even if it stands for days.
What can cause this, can there be a check valve that don't close properly, e.g. in the scavange pump, when engine is cold letting the oil to drain into the sump and further into the cylinders, or is it caused by something else?
There is no evidence of smoke during normal driving and even after 7000 km no drop on the dipstick can be seen.
The car is a 86, 911, 3,2l

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Arild

[APKhaos]

It's the 911's way of saying 'Please don't run me unless there is time for all my fluids to reach full operating temperature'. Short runs with cold shutdown = high wear rates.

That said, the 3.2l is renowned for leakage in the valve guides. Nothing to worry about as long as your oil consumption is less than 1Qt/800 miles. Mine has 145,000 miles, and ocassionally puffs on startup. Its a quirk.
Tony K
85 Carrera

[Early_S_Man]

Arild,

I doubt if this is an indication of any serious problem.

There is no check valve in the oil pump. The two relief valves are external to the pump, ome in either side of the crankcase, but only the lateral one on the left side can dump into the sump.

When cold and oil pressure is at its' highest, the piston squirters may be the culprit ... leaving a large quantity of oil on the lower quadrant of the cylinder bore and under the piston crowns, which the oil-control rings have a hard time coping with on the next startup. Is there any unevenness to one side or the other where the car is parked, such that one bank of cylinders might 'catch' and retain a large amount of oil under the piston crowns ... if that side was tilted 'downhill' -- so to speak?

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler