White smoke on start-up

[Peter Aston]

Hi Everyone,

An old chestnut this I know but: I rebuilt my 1987 930 engine last winter for broken studs hoping that the more often than usual white smoke on start up might be cured with the new rings, guides and seals but no it still does it - maybe a little less.

So, as I hadn't rebuilt the turbo, no apparent need, no spindle end float, perfect blades, but I have noticed an oil film in the intercooler so suspected the turbocharger oil seals, so rebuild the turbo.

Today I've asked a respected turbo rebuilder who has said he's loathe to take my money to rebuild it because it probably won't cure the problem, our turbos have a metal to metal oil seal and a little leakage is unavoidable so save your money and live with it!

What's everyone's experience with their cars?

Thanks,
Peter

 

[vic cohen]

1986 car,very similar ,i.e. head studs and loads of stuff at the same time ..car had done GENUINE 19500 miles ...........similar conversation re turbo , have NOT rebuilt ........still smokes !
now reached 41 000 miles ,uses very little oil , no visible leaks...............goes like stink !
sorry think one has to live with it
have had 3 0 turbo and 2 993 gt2 s all smoked a little

 

[james.cookson]

1975 3.0 - For a long time I had the problem of white smoke on start up. In my case we eventually diagnosed it as a pressure difference between oil coming into the turbo, and oil being scavenged out via the scavenge pump back into the oil system
On start up the cold oil was flowing around the engine area and was being supplied at a higher pressure and volume than the scavenge pump could deal with. The oil therefore flowed through the point of least resistance, which was the turbo bearing. This surplus oil would then flow out of the exhaust side of the turbo where the warm gasses would vaporize it into the white smoke. Some would also flow into the inlet side and be partly burnt off in the engine but this was being masked by the copious quantities of white smoke.
Once the engine warmed up a combination of warm thinner oil and the oil thermostat opening offering more space to dissipate the oil in would result in the white smoke stopping, usually after about 5 mins of running. The white smoke is from vaporization of oil, not from oil burning (this would be blue).

I changed the scavenge pump and checked all the oil paths were clear back from the catchment tank below the turbo. The other thing is when I start mine I am very careful not to rev it during the first few minutes. I watch the oil pressure gauge like a hawk and try to keep it below 100.

Keeping the revs down is not easy but as I garage the car I can let it 'settle' for a few minutes on start up using the hand throttle to just keep the revs above 1,200 rpm.

I have had my car for 10 years and spent the first four years with the white smoke problem. Since I have done the above I have not had any issues with white smoke.

Should I forget to be gentle on start up, and rev it then I can re-produce white smoke and must then wait for the engine to warm while it looks like I have a very poorly Porsche rapidly killing the planet with its awful fumes!

I was staggered at how "wet" the system got when the white smoke occurred.

I hope this helps.