About a year ago I notice a large cloud of white smoke during start up of my 2002 Carrera. This didn't happen very often and everything I read said not to worry. I knew it wasn't oil smoke as the smoke was white and had a sweet smell to it.
In the last month I seem to notice the white smoke more often but never noticed a drop in coolant level.
Two weeks ago I notice that I had a major leak in my expansion tank and had it replaced. Since the replacement, there has not been any white smoke at start up! Coincidence? Maybe.
I now believe that the white smoke that many of us have witnessed in the past has something to do with coolant leaking.

Today, I replace a water hose (small curved hose) at bottom of the engine and had coolant all over the place. Once I started the car, there was that cloud of white smoke, until it burned off my engine. I will let you know if I see any additional smoke.

 

At least you have the history of it and keeping an eye on it.... how long does the white smoke lasts? How does your oil changes look?

 

A bit of brief oil smoke -- which will have a rather light color (grey/white with possibly a very light bluish cast to it) at start up is nothing to worry about.

Any color of smoke (though if coolant the color will be that of mainly water vapor which which have a pretty white color to it) that has a sweet smell is almost certainly coolant. This is something to worry about.

It could possibly be the coolant tank leak was allowing coolant to leak onto the hot engine/exhaust and the smoke (vapor if you believe it arose from coolant from being passed through the engine) may not have come from the engine but outside of the engine.

If you have any reason to believe coolant is getting into the engine a draining of the oil from the crankcase/engine sump and if the filter housing not upside down removing the housing and carefully dumping its oil into a clean drain pan and then looking for any signs of coolant/water is called for.

There should be none. An even more telling check is to send an oil sample out and have the oil analyzed for any signs of anti-freeze chemicals in the oil.

Yet another check is to examine the spark plug tips. If any water is getting into the combustion chambers those affected will have their plugs clean (steam clean).

If you find any water/coolant present in the oil or any signs of combustion chamber water presence...

Coincidence, I'm almost 100% sure. The overwhelming number of 'smoke' at startup is just oil residual oil that arises from a less than 100% efficient AOS mainly, with the lesser possibly some oil is coming in past the rings as the engine sits after being run. (An engine that is shut off before it gets up to temp leaves a considerable amount of oil clinging to surfaces/parts that will have this oil ending up collecting on the bottom of the cylnders.)

What keeps my confidence level from being 100% is I'm not sure what role -- if any -- a bad AOS can play in putting coolant in the engine. My 02 Boxster's AOS has no coolant lines but IIRC the 996 engine's AOS does.

If so a going bad AOS can put some coolant in the crankcase and if so this coolant in the crankcase is available to create a bit of water vapor at the exhaust as the oil heats up and this water vapor of course gets routed to the intake manifold (because the AOS is likely at first to be bad only intermittently and it will work good enough sometimes) which of course is 'burned' in the engine and comes out the exhaust as a cloud of white smoke (really of course water vapor).

Sincerely,

Macster.

 

The cloud last 2-4 mins. and once it's over it's over. The oil is fine, as I regularly change it every 5k miles with Mobile 1, 0-40. There is no water in the oil.

 

Just changed my AOS on my 2002 C2 Cab. This summer got a couple of clouds of smoke after startup. Looks good so far.

 

2-4 min each start up?..... that seems like a long time. How long does it sit betwee start up? days, weeks, months?

Try letting it idle for a few minutes before shutting it down.... see if that helps.

 

My normal thinking is smoke from oil at start up has leaking valve stem seals at the top of the list. Engine is turned off and hot thin oil is allowed to drip into a cylinder or more. As far as coolant I'd diagnose quick to eliminate or verify that one. Or you are blowing a little oil all the time into the exhaust but not racing the engine enough during normal use so that oil soaks back over to the engine exhaust side ready to be burned on first start up. Of course I'd believe one of the typical problems.

Doing a cylunder pressure check would help diagnose to eliminate sources. Checking plugs also. Checking exhaust with a piece of paper to absord the smoke. All of these get you half way there. A wet plug at extraction when cold or hot, blah blah blah.

 

Hi friends. İ am new user. I am from Turkey.I have a 2003 996 Carrera Cabriolet 4.
and i see white smoke at start up 4 or 5 times. ı asked porsche services.
he said this is oil burning or like something.this is make when the engine is cold.i dont
know but it isnt normal. first time i am afraid very much i think i will burn but i am not afraid of me i afraid of my car . sorry about my english. i cant understand your writings very good and i cant write very good. . good days.