2001SaxsterS

Ok, I know this topic has been done to death, but the answers are so far across the board I thought I'd post my specifics.

My car is an 01' S model with 108,000 on the odometer, but only 50,000 on a replacement engine. Noticed some whitieish smoke (or steam, I really don't know which) coming from the tail pipe today on startup. It also seemed to be running rough. Both of these problems went away after maybe 30 seconds max (probably less actually) and it drove fine after that with no warning lights coming on. The smoke wasn't a massive amount. I'm familiar with the "cloud of death" as that is what happened that required me to replace the original engine. This was nothing like that and it didn't smoke when I was driving. Probably wouldn't have noticed it in fact if I didn't have to get out of my car to close the garage door.

Couple other things to mention...car hasn't been driven much for about three days. Actually, I picked up a nail in my tire on Friday and found it flat on Saturday. I've read about oil or moisture burn off that can occur at startup and that it seems to be worse when the car hasn't been started or has only been moved a short distance. Does that sound like it could be the case. Prior to this smoke all I did since Friday was to back it in and out of the garage to make sure the spare was working well. Also, I saw someone say that they thought the angle it is parked (ie on an incline) could contribute to this problem. Mine wasn't on an incline, but I obviously had to jack it up for the tire which I suppose could produce the same affect.

Any thoughts on what this could be? Hopefully nothing, but having spent $12,000 a few years back to replace the first engine my mind is jumping to the worst possible conclusion.

2001SaxsterS

Oh, forgot to mention. Oil level is good. Coolant level is good and it looks clean. When my last engine went it looked like a milkshake so I checked that right away.

Dendrobium

Sounds like the oil burn off at startup. Other than that, if it were alot of smoke it would be the oil separator - usually costs anywhere in the six to seven hundred dollar range to replace.

2001SaxsterS

I definitely wouldn't say it was a lot of smoke. When my first engine bit the dust it looked like the space shuttle blasting off. Just a massive cloud. This was just a little bit wafting out of the pipes. I wouldn't have noticed it just from looking in the mirrors, but I had to get out of the car to close the garage door. That previous experience has made me very wary though.

Macster

Given the circumstances of the event, the smoking I believe is nothing to worry about. Sometimes when my 02 smokes the engine does run a bit rougher than usual at startup and shortly thereafter. Nothing gruesome. Only noticable because the engine's otherwise quite smooth at startup.

If the smoking persists after startup, is a frequent or every start event, if the engine keeps running rough, a check engine light comes on, then you can start to worry.

Sincerely,

Macster.

Dale_K

Fairly often I have a small cloud of oil smoke on start up, too. Maybe about 1/3rd of cold starts but never on a warm motor restart. It doesn't worry me much but I'd like to know what's going on so my question is; what is the source of the oil?

Seem like only 3 possibilites.

1 - accumulation in the intake tract. You'd think it would be more consistent if this was the case and you'd also see it on a warm start.

2 - oil getting past the valve stem seals. Unlikely to be the exhaust valves since they point down.

3 - oil getting past the rings. My old BMW motorcycle (horizontallly opposed engine) would do this but only on the low side cylinder when the bike was on the side stand. The Boxster sits dead level in the garage and I can't visualize how the oil could pool against the ring.

Anybody know for sure why we get the cold start smoke?

2001SaxsterS

Below is some info I had found on http://www.986faq.com/10-0/problems.asp#013 that sounds like what both of us have experienced...

White Smoke From the Engine
Diagnostic: White smoke comes from tailpipe when the engine is started.

Cause: Oil residue under the pistons heads.

Details: The Boxster engine uses a flat six cylinder design. Because of this construction, oil residue remains under the piston heads and burns off at every start up. This can produce a white puff of smoke. It should only lasts a few seconds. This is normal, and no correction is necessary.

Time in Shop: None.

Repair Instructions: None.

Notes: None.


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2001SaxsterS

Well, I think I'm in the clear. Have logged over 100 miles since that incident now with no more smoke, warning lights, or other problems.

Macster

My belief is the oil which causes the smoking comes into the engine via the intake and this oil comes in past the AOS (air/oil separator).

The short reason is the AOS sucks sucks in that it simply under some situations can't remove enough of the oil vapor that is a normal component of crankcase fumes.

As a result the crankcase fumes routed to the intake manifold contains oil vapor and when this oil vapor contacts the intake walls -- cool I might add -- the oil vapor turns back into fluid.

If the engine is warm and likely being driven down the road it would take a keen eye to spot a bit of smoke.

But if the engine, even if warm, was shut down soon after the AOS passed along a bunch of crankcase fumes laden with oil vapor, then this oil vapor would turn to fluid and gravity would have it in a combustion chamber or two or at least puddled on top of the closed intake valves available to incomplete combustion the next time the engine was started.

Now if the engine was relatively warm at the next start the oil might not result in much smoke because the hot engine internals would help combustion. Then the hot converters would further process this hydrocarbon.

The AOS's performance can be made worse if the engine is overfilled with oil, the oil is heavily contaminated with water and unburned fuel (normal by-products of combustion) or possibly the wrong oil, type or viscosity.

If the oil was coming in past the rings the engine would smoke every cold start since at least one cylinder would be positioned just right -- whatever that is and I won't take the time to detail what I think this is -- upon every cold start.

The valves are not submerged in oil and they lay almost horizontally so it would take some pretty active oil to seep past the seal, along the valve stem/between the stem and the guide, and make its way into the combustion chamber. And I note that if the seal/valve stem/guide combination would allow oil past it at a standstill when the engine was running and under a low pressure condition like at idle the engine would emit a oil cloud all the time.

I have spoken with senior Porsche techs some about this smoking upon startup. They see it quite frequently since cars on the lot, new Porsches and used Porsches, get started often but run for only brief periods of time.

The techs follow the quidelines that as long as the smoking is at cold start, is brief, and not accompanied by any other untoward engine behavior, check engine light, it is normal.

I note when I checked out what would prove to be my new 02 Boxster in Jan. of 02 upon cold start the exhaust smoked a bit. I noted this. We took the car out and put around 15 miles on the car and of course the car ran beautifully.

Back at the dealership though we were unable to reach a mutually agreeable price and I left.

But I came back later and asked the engine be started again. It was. No smoking. And I adjusted me offer to cover the flooring cost the dealer had in the car and I bought the car (at about $5K under list).

That was in Jan of 02 and here it is Oct '11 and that engine has covered nearly 250K miles. It still smokes upon cold start once in a great while. The engine is original of course, but I'm on my 3rd (or is it my 4th?) AOS.

Sincerely,

Macster.

Dale_K

I don't understand that link that says "oil under the piston heads". If they mean below the piston the only way it could get to the combustion chamber would be past the rings. That could be a possibility and remain a semi-random event if it got past the ring end gap. Only occassionally would the ring gap line up at the bottom of the bore and permit oil to flow past. I believe horizontal Honda motorcycle engines, like my old Valkyrie, have the piston rings pinned so that they can't freely rotate in the piston ring groove. The end gap is never at the bottom of the bore and my Valkyrie never smoked even though it leaned on a sidestand whenever it was parked.

I like the intake tract theory but admit I really don't know. I've tried a little experiment where I run the engine to redline once during a drive at full throttle and so far I've never seen an oil puff on the subsequent cold start but I haven't done the experiment enough to be conclusive. It's nice to run the engine to 7,000 "for science", lol. My theory is the high velocity throught the intake would sweep up any oil laying around and thus be smoke free the next start.

dallison28

You shouldn't have any real issues, just drive it.

logray

You could try installing the larger motorsports AOS for the Boxster, however this would only address purple/blue smoke at higher RPMs during track use and high g-forces.

http://www.planet-9.com/reviews/caym...seperator.html

If you want to test your crank case vacuum to see if your AOS has failed and is causing excessive vacuum (and hence excessive draw/oil burn off), here is an inexpensive and easy way to do that:

http://www.renntech.org/forums/tutor...for-a-bad-aos/

cretinx

I'm going to be honest - I've owned 2 boxsters and when I let them sit a long time they give a nice puff on startup and then run clean - seems to be pretty standard.

Macster

The techs I talk with tell me that almost every car that comes in and for which they have reason to have access to the intake manifold the manifold's interior surfaces have an oil film. Often the engine is overfilled with oil which doesn't help.

The oil vapor that I suspect is ultimately responsible for the occasional cold start smoking is not a red line thing. Drivers of these cars seldom hit redliine -- there are of course always the exceptions -- so it is the more mundane, everyday usage that creates the oil vapor load the AOS is unable to deal with.

Almost always the engine runs at low rpms and even idles some before it is shut down. It is during this time the oil vapor is produced. The air flow through the intake tract is not that violent and thus would not sweep all of this oil into the engine before the engine was shut off.

Since the oil and engine is hot and the intake gets hot from the heat soaking from the hotter parts of the engine this warms the intake tract and thus this oil from the vapor now can find its way down into one or more combustion chambers to be available next time the engine is started.

The pistons - the underside of the piston's crown -- is drenched in oil courtesy of an oil jet that sprays a considerable amount of oil at the underside of the piston to help cool it. (Porsche claims this oil jet lowers the temp of the piston by 50C.) When the engine is shut off this oil of course will run down and some will flow over the holes that lead from the oil control ring groove.

But the oil control ring presents with the engine not running a pretty good labyrinth seal, not to mention the two compression rings.

IIRC the rings of the Porsche are not pinned and theoretically can rotate and it is possible in doing so one or more rings end up with their ring gap at the bottom of the cylinder. But the cylinder finish is not condusive to the ring rotation so the rings I would hazard a guess rotate very little if at all once the rings are seated and they seat very quickly after the engine is first started up.

It really matters not though where the oil comes from. What matters is these engines smoke upon cold start once in a while. It is normal.

It is normal and nothing to really fret over as long as the smoking is not accompanied by *real* engine misbehavior.

I might point out that at least in my experience when the engine does exhibit some misbehavior along with some smoking the problem proved to be the then current AOS.

Sincerely,

Macster.

cretinx

I don't know if that's a shame that so many namby pambys pick these cars up just for the status, or if its a good thing because that means there are plenty of used examples for a vulture like me to scavenge?