AOS or cracked head?

I have searched quite a bit, but so far, nothing conclusive and was wondering if any here can point me in the right direction. 2002 C4S 28K miles. When I got the car, never saw it smoke upon startup. It was not until approximately two weeks ago that I turned the car on (after resting overnight) and I got a HUGE (size of a small SUV) plume of white smoke coming from the passenger side muffler only. After 10 seconds of idling, no more smoke. I did drive it like it was meant to be driven the night before. Fast forward a few days and in some instances, again, cold startup, I have gotten white smoke, but only about the size of two shoe boxes, from the passenger side muffler. Not necessarily redlining it the night before. Once the car has warmed up, or used a couple of times during the day, no white smoke, it is just the first startup of the day that yields the white smoke. So, my doubts are: AOS or cracked head? What exactly does an AOS failure cause? Can I use my car until it finally totally breaks down (assuming its a failing AOS)? How can I properly diagnose that it is a cracked head instead? Thanks in advance for your replies and observations.

Another tale of woe. We set off from Cheshire to France early the other morning, cold but lovely sunny day and not too much traffic. Imagine my surprise when after paying the M6 toll, the drivers window gave out a loud crack and wouldn't go back up. Cue a 530 mile trip with the window stuck down. Is that a record I wonder! Thank goodness for the heated seats and steering wheel. The day after arriving in France I took the door panel off, followed by the inner panel. I found that one of the plastic window regulator wheels had cracked and buckled causing the cable to dismount and that another cable had bunched up and become jammed. That would be an expensive fix via the Bentley route, £333 UK approx plus delivery. So, I have taken a chance and ordered a cable repair kit and a new regulator for a VW Passat. The Passat part will donate a single pulley wheel which will replace the broken one. It's a bit of messing about but a lot cheaper if it works. Total cost for both parts is £46. Wish me luck. Also, on this topic, I found from an Audi forum that window regulator failure is a common problem and one which has been acknowledged by Audi to the extent that some folk have had them fixed for free. The Bentley/VW/Audi regulators all look very similar in construction and only vary in shape by the look of it. So why is the Bentley part so expensive? Yeah, I know, I'm paying for the name. I will update you all soon.

Check your coolant to ensure there's no innermix. Sounds like a AOS though or condensation. Make sure your not over filled. Do you have oil consumption? Some Porsche blow smoke every start-up, it's the way the oil settles. If it's just a puf when starting it could be normal, but my best guess AOS. White smoke = water Blue smoke = oil Black smoke = gas

Welcome to France!! Les good luck with your window, it happens to me once in the Maserati. It was a real PITA to fix!! I just don't understand why they don't replace that little plastic piece, the same in the Maserati, by a strong metal piece! so much for our , so called, ''luxury cars''

cheap/quick test to check for bad AOS: try to remove oil filler cap while engine is running. If cap is hard to remove + car's idle gets rough while cap is off = most likely bad AOS.

Hi Ulstrup. I did actually think about getting a wheel made up in metal but the cost of the complete VW regulator is so low as to make it not worthwhile. I just hope my plan works out. Regards. Les.

I heard about the filler cap removal, but it is my understanding that there should always be a vacuum there, so to proper determine this, I would need some sort of special tool to accurately measure how much vacuum pressure there is. I just turned the car on (been off for nearly 24 hours, did redline it twice 5 minutes before parking it) and no puff of anything on startup. The smoke is random, it is not every time that I turn the car on. If the car is warm, then definitely no smoke at all. On the occasion that it does smoke, it's just on initial startup after it sits for a while.

Well that didn't work. The cable was so chewed up at one end that it was impossible to measure correctly and that's very important with these systems. So, I have had to bite the bullet and order a complete new regulator from Flying Spares. OUCH! Les.

Take it to have it looked at a different place. Before it explodes.

My passenger side front window regulator went with a loud crunching on the way back through France to Eurotunnel. A similar event to yours in the plastic wheel cracked, the spring tensioner also broke and the wire tied itself in a knot: It really is a dreadful design for such a heavy door glass. The cruciform metal arms used by many other manufacturers would be a more robust solution. Graham

IMHO...neither. Porsche flat 6 engines often eject a bit of white (oil) smoke upon cold start, after sitting overnight. With the flat 6 engine any oil film in the cylinders has no place to drain out (i.e. can't drain back into the crankcase), so when you start your car you get a puff of smoke when the oil burns off. If you had a cracked head you would get intermix--oil in water, water in oil. You can easily check for this by inspecting the condition of the coolant in the reservoir. If it's green or pink--you're fine. If it looks like a chocolate milkshake--intermix. Most often a bad AOS results in continuous oil smoke, particularly during high RPMs. Not a small puff on startup. If you're really worried have your mechanic check it out. From what you've told us, I think what you're seeing is normal.

....truly horrible ...designed to save pennies...the engineers know better but boss says do it cheap...how have things gone since then...JimB

I was late for a meeting this morning, so I did not have a chance to look for intermix, but will do so later today. I did notice that this morning, as well as yesterday morning, that no smoke came out at all. Will check for intermix later and report back. Just find it odd that in one case, there was a huge amount of smoke, few days later, not so much, then once in a while, just a bit of smoke.

Quotes source post: 3844710

Just curious, did you happen to get a wiff of the smoke? What did it smell like? Quote:

I did. The smell was not as "sweet" as coolant, but not as "pungent" as raw fuel. It was not as if no cats were on the car either. My meeting got pushed, so I am off to check for intermix now.

OK, took a few minutes and went downstairs to check this out. When I turned on the car, no smoke (just like earlier this morning and yesterday morning). Observations: 1- with the car idling, I removed the oil filler cap and even before lifting, I could clearly hear a air "intake/sucking" noise. The cap was very easy to remove. The car seemed to change idle, but ever so slightly, definitely not rough idling nor want to die out. So, removing the oil cap requires not much effort and just makes noise. 2- removed the coolant cap (sucker was on TIGHT!) and looked at it. Not really sure what to make of it. Does seem a very light, even, tan/dirtygreen color, but definitely no oil residue or drops on top of the water. I know oil and water don't mix, so i would have expected to see some sort of oily film and that was definitely not there. I would assume that if there is intermix, it would at least look like when you pour gasoline on top of water (think refilling your boat and you get overspill). The color is definitely not pink, nor "vivid" green, but perhaps it is a pink/green that has not been changed in a while, thus the color seen? I don't have the service records of the vehicle (dealer has it and wont release them to me as someone else paid for those services) so I am unsure as to when it was the last time a coolant flush was done. Like they say, a picture paints a thousand words. See below.

I hate to say this, but it looks like the first sign of intermix. Is it thick? And if so, it might not ba a cracked head, it could be a bad head gasget, or the cooling system.

Will stick my finger in it later when it's cooler. Seemed to me that it was very thin and not thick/cloudy at all. How can I precisely determine what is going on? Unfortunately for me, the local dealer lacks trained professionals and it has been multiple instances where I have had to tell them exactly what the problem is and how to fix it. There are no other local dealers in the country, so I am stuck between a rock and a hard place, hence me asking for advice elsewhere. Regarding cooling system, I am actually amazed as to how cold this car runs compared to my previous 3.4 C2. This one takes a good 15 minutes to reach ±176º (since my car is Euro, it is labeled as 80ºC) and this driving in stop and go traffic in 90º+ weather. Only in really extreme hot days (100º+) have I seen the needle barely pass the "0" in the 80º marker.

Quotes source post: 3844915

I'll look at mine when I get home. One sign of intermix is there will be a oil film on the inside of the cap, look at it. Also, for grins go to an auto parts store and get the strips to test the coolant, it should be 50/50 and perhaps the previous owner mixed it too strong or it's too old. Quote:

I had the same symptoms on a 2001 C4 with 55K on the clock, Did a leak down test found one cly out of spec. it had a stuck oil ring.

Well, I looked at mine and the coolant is yellow and clear. You know, it may be all you need is a radiator flush and new coolant. The smoke may be normal wear and tear.

Quotes source post: 3846076

Mine looks similar to the original poster's and so does the jug of Porsche Antifreeze sitting in my garage. Quote:

I haven't been able to sleep well for the last 2 days just thinking about this. The coolant used in Panama (Porsche label) is pink in color, so I am HOPING that what has happened is that the OP used some other coolant somewhere else. Tomorrow should yield the definitive answer when it goes into the dealer for a complete coolant flush and pressure/vacuum test of the cooling system. Let's hope that it is nothing after all. For the record, the car has not puffed any kind of smoke since I started this thread. Weird..

Quotes source post: 3847364

Good to get the cooling system flushed. You know, you may have gotten some gas that had water in it and that's what caused to smoke. FYI, never fill you car with gas when there is a delivery truck filling the tanks. Quote:

Hi fellas: car is currently on a lift having the coolant taken out. Tomorrow morning they will flush it a couple of times as well as pressure test it. Once that is done, new "pink" coolant will be put (hope they get it right!). Told them that the test should last at least an hour to make sure. Here is to another sleepless night!

Quotes source post: 3848276

Good luck, I hope this works out well for you. Quote:

Just a few things.. -If the car is warm, it is normal for the cap to be on real tight. -AOS can cause oil blow by on startup. Basically oil doesn't go back into the sump, instead goes into the intake. Hence the burn up. Just seems to accumlate and not be burnt until startup. I have fixed this problem multiple times with replacing the entire AOS system. -Coolant turning yellowish sometimes happens when the wrong coolant is used to top off the system. Ex: a person blows the expansion tank and has to resort into using something green on the road. It turns into the color shown. At 28k miles I do an engine out service. IMS bearing, plugs, clutch disk, coolant flush, all fluids, and the AOS system. I also make sure the line is clean under the AOS..use a wire to clean it out. This makes sure the AOS can drain properly. Otherwise it'll just plug up again. I don't argue the IMS bearing, I have my opinion and experiences and that's all I can share. Sometimes after a hard day on the track, we can see some burnt oil on startup. While this is rare, and as long as it isn't consistant, it's normal.

Well, I just picked the car up from the dealer and it is full of fresh Porsche pink coolant. Let's hope it stays that way forever! They claim that the "coolant" that was in there before my flush was not really coolant, but instead, 95% water and the color seems to be just from dirty passages. They refilled it and took all the air out of the system and now are confident that I have no intermix problem (they did a vacuum test and no leaks found in over an hour). They claim that the smoke I used to see was from their overfill. Truth be told, I have not seen smoke in weeks and each time it got progressively less. I am going to stop worrying (for now!) and just drive the heck out of it and enjoy it as much as possible. Too bad the rainy weather finally arrived, but as soon as there is a dry moment, watch out!

Quotes source post: 3852979

I'm happy your problem has been solved, enjoy the ride. Quote:

Well, my joy didn't last too long... Today I took the car for a very spirited drive (80-120mph, maybe 10 times revving all the way until it automatically shifted, ±30 minutes) and then I drove for about 10 minutes at a very conservative 40-50mph to "cool things off". Parked it for about 6 hours. Just went to run an errand and when I started the car up, smoke out of the right muffler. Because my car is parked in a dark spot I could not tell if the color was white or blueish. It was not much, but there was definitely smoke upon startup. Going to wait for the car to cool off completely so I can open up the expansion tank. IF I have intermix, would the color of the coolant change immediately or does it take days for it to turn from pink to brown? Perhaps this is the normal smoke after spirited drive? What concerns me is that it only comes from one side (right). Never a dull moment with this car... Now my window microswitches on the driver's door are acting up. What's next?!

Well, car cooled off for ±5 hours and I decided to start it to check for smoke. On the first try, no smoke! It idled for about 1 minute then I shut it down as I wanted to check the coolant. Opened the expansion tank up and looks like it did three days ago when it left the dealership after its flush. Ten minutes later, I started the car again and once again, no smoke. I am hoping that the small amount of smoke I saw earlier today is directly related to the "Italian Tune Up" I performed earlier this morning Last night, I had the opportunity to talk to the son of the original owner of the car and he told me that the person who owned the car before me (I am the third owner) used to drive short distances and never really used it as it was designed. Perhaps all these little things are largely due to the fact that I do use my car as it was designed for Coolant pics:

It is not uncommon after a hard flog, cornering to have a puff on start up. Sometimes the AOS cannot deal with the excess and due to engine design oil can tend to enter into the cylinders and cause this. My car has done it once and will do it on track days. My indy, a well know P - Car guy, said it is normal to have a puff. I don't like it but I don't see it on day to day driving. I would monitor oil and coolant levels and enjoy the car, a little puff on start up seems to be ok. What is the oil fill level like on the dipstick? I usually run in the middle of the dip stick and 1-2 bars down on the electronic guage.

The other day, after the "tune up", when I measured on the electronic gauge, it read 1 above the minimum level (3 bars total out of the 8 lit). Today, after normal driving, it read an additional 2 bars (about half way between the two marks). In both instances, the car was fully warmed up and on a level ground. Yes, I know the dipstick is the best way, its just that I never got around to do it. Today I had the opportunity to use the car on 3 separate occasions and it never spitted out smoke on all 3 start ups. Tomorrow I leave on a 8 day trip and we shall see how it starts up after sitting for a while.

GOB...a small puff of oil smoke on cold start is COMPLETELY NORMAL for the Porsche flat 6 engine. Not only has that been concluded by us amateurs in this and other Porsche forums many times, but such was also published in Porsche Panorama (PCA's official publication) in its "Tech Questions" section several months ago--that time in reference to a 997. Set your worries aside and enjoy the car.