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    997C2S exhaust, 1 side more "contaminated" see pic

    Hi, I have a 997 C2S, production date june 2007, bought it new in November.

    It currently has 1300 miles on it, and I added 0.5ltr of Mobil1 at around 600 miles, since then no oil consumption according to the oil level indicator....

    When I look to the rear of the car, and look at both sets of exhaust pipes, there is a difference in "coloring" between the two sides.

    The Left side is a lot more black, and the right side, a lot more gray-ish.....

    Should I conclude that the right side cylinder bank (which I believe corresponds with the left set pipes) "spits" out more oil or other contamination...??

    Anybody else seen this before??

    Thanks a lot, Pete

    Re: 997C2S exhaust, 1 side more "contaminated" see pic

    SOV, take your car to the dealer as soon as possible. It could be a faulty sparkplug, or as it happened to me, cylinder 6 was sccored and had to replace the engine (the whole ordeal took about 2 months). I hope you only have to replace a sparkplug.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Here's what PCA tech expert sez in a Q&A from 2005:


    I'm getting heavy black soot on the right exhaust only. It's bad enough to coat that area of the body near the right exhaust pipes. I'm not noticing any smoke. I've broken the car in carefully. Oil consumption is exactly 1 QT/1000 miles. I've added 3.5 QTs in 3500 miles. Any recommendations or thoughts as to the cause?

    You might be using oil only in maybe one cylinder on the right bank and that is giving you the black soot on the exhaust. Wait until you have about 6000 miles on the engine and see if the soot goes away after the engine breaks in. If is doesn't, I would do a cyl leakage check on the right side. There might be a ring problem there

    Peter Smith - PCA WebSite - 8/8/2005


    Here's another PCA Q&A on soot AND an important link to another thread on this disturbing symptom.

    Sorry to hear of this demoralizing problem again. Good luck! Keep us posted:


    Re: 997C2S exhaust, 1 side more "contaminated" see

    1,300 mi in 4-5 months?

    Lots of short trips I suspect...
    Do your car a favor..... go out and do some long haul drives!!

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Hi, thanks to all for the replies and advice.

    Just to give some more info:

    I live in Boise, Idaho, and I took delivery of the car in early December, since then we have had snow on the ground (or very cold conditions with sandy roads) for almost entire December January and February.

    I was able to take the car out 1 time in December, and as of the last 2 weeks, a little more frequent. They have started to sweep the roads.

    I never drive less then 20minutes, make sure the car is warm on both water and oil, and if this is the case, I do get on it.

    I did not go above 4100rpm till after ~650miles, and then in about ~250miles I started moving up in rpm's (again if the car was both warm on water and oil).

    Currently I am at ~1300miles and have started to redline (running through the gears) it occasionally when the car is hot.

    I would be interested to hear if I need to do anything else (driving wise), or what is considered as a longer haul or trip.

    I always used Chevron fuel, recently started using Shell V-power, but am thinking that I will switch back to Chevron, as I just noticed that Shell here uses 10% Ethanol in their V-power.

    Thanks again, Pete

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Sounds like you're doing everything fine. AFAIK, As long as it has been driven a long enough time for water and contaminants to be dispelled the car can sit parked for weeks without detriment.

    IMO, it's impossible that what's going on with your car has something to do with your driving habits. It's a problem for Porsche to solve; and probably a PITA for you while they solve it.

    I think a long haul trip this way. When the OIL reaches the boiling point of water, how long would it take for a _possible_ 1/2 cup of water in the crankcase to boil off? Twenty minutes of more-or-less steady driving at operating temp of the oil seems long enough for me.

    BTW, under ideal conditions like a lab beaker on a bunsen burner, when the oil goes beyond the BP of water you have to assume all the water is gone. Last time I checked our oil temp typically goes well beyond the BP of water.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    I just got back from the dealer. Our mechanic (yes we have 1 dedicated for Porsche at our local dealer), looked at it, and says he has seen it before.

    Given the fact that I hardly have any oil usage, he suggested to clean it, do a few 3-4 hour drives instead of my 30-45 minute drives, and see if it makes a difference.

    Here at the dealer, they have seen it very few times, but on 1 occasion, it led to mechanical damage (scraped cylinder wall do to ring failure), and an engine was swapped out. The mechanic did mention that this was done under warranty, even though the data logger showed that there were some rpm 'spikes' that could indicate faulty downshifts (over-revving).

    I will clean it in the next couple of days, and try to go for some longer trips.....

    Will update if anything changes, Thanks again, Pete

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Sounds like a pretty slick response to me.

    If you did any bad downshifts I think you'd remember them. Chances are you'd have to be driving your brand new car like a crazy man to do it.

    If there's zero chance of you having done the bad downshifts He's talking trash to make you nervous.

    We all know Porsche has seen this "uneven soot" problem _many_ times in the past. They're hoping they can put you off as long as possible, hope you'll "go away," and only do the engine switch if they absolutely have to because it's the ony way to fix it AND you demand it.

    IOW, since they have seen his problem many times, in a perfect world they would take your car in, do the exact necessary tests to deduce that it IS the bad cylinder (or whatever they discovered as the cause) and then order you a new engine if that's the only way to fix it.

    I'm guessing that in an "Excellent" world they could easily determine the cause and order a new engine if necessary all in one day.

    You can clean the tips all you want and drive differently but I personally know the chances are "excellent" they will get just as unevenly dirty time and time again... .

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Update 1:

    Cleaned the exhaust pipes with 1405 miles on the odometer. This was actually more difficult then I thought, lots of hard sticky dirt on them (in the beginning it felt like the stuff had eaten in the pipes).

    Drove one straight trip of 177miles, got a nice speeding ticket, but it was a great ride.

    Came home, and took a picture of the exhausts.

    The white stuff in there is "MOTHERS" mag & aluminum polish that I must have rubbed in the cracks, and then later during the drive got liquid due to the heat.

    The pipes were completely dry.

    There is still a little difference in color, but I believe that to be there from the earlier discoloration. The general color of the pipes looked exactly like they did after cleaning.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Update 2

    -Cleaned the pipes (to remove the "Mothers" polish residue), drove another straight trip.

    This time 182miles, no speeding ticket....

    Let her run (till ~7000rpm) on numerous occasions (50+ at least).

    Came home and took some pictures of the exhausts.

    I don't know if it has to do with the real longer trips (instead of 30-45 minute trips), but it definitely does not seem to hurt, as both pipes were again completely dry, and the coloring of the pipes is the same as ~360miles ago after the first clean....

    Thanks for all your tips and advice, if something strange happens in the next 2000miles or so, I'll give another update.

    Last but not least, during the last two trips (~360miles) of long and mostly sporty driving, their has not been any oil usage according to the electronic indicator. The car now has ~1800 miles on the odometer, and I have only added 0.5liters of oil at ~600miles, since then the level is stable.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    close up left pipes at ~1800miles

    Re: 997C2S exhaust, 1 side more "contaminated" see

    close up right pipes at ~1800miles

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Got my fingers crossed for you soV. I had the "same" problem with my 997C2S. Cleaned and compared several times but problem never went away until I traded in the car. Hopefully your outcome will be nominal.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    right exhaust might have leaks.. check the bolts on the right exhaust(the area between the cats and exhaust/2 bolts)

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Hi MMD,

    Thanks for your reply. Can you say a little more about your oil consumption when you had your 997 C2S (with the similar issue).

    What did your dealer/mechanic have to say about it?

    Was it the same discoloration, and at what intervals did it seem to come back?

    Thanks so much, Pete

    Re: 997C2S exhaust, 1 side more "contaminated" see

    Thanks yellow997s,

    I will try to check if I can see if anything is not ok. I assume you mean the connection between the end of the right cylinder Cat and the muffler of that cylinder side...?

    Which would be more on the left side of the car (looking at the back)?

    Thanks, Pete

    Re: 997C2S exhaust, 1 side more "contaminated" see

    As I recall, there are two catalytic converters --one for each side of the engine. Each converter has an O2 sensor located at its inlet and also at its outlet. The Motronic then adjusts the fuel mixture according to the signals received from these sensors. Since the driver's side exhaust is a little sooty, it is the passenger side cylinders that are running a little rich (the exhaust pipes cross-over underneath the car). Since the MIL light is not being set, I have to think one or the other of the passenger side O2 sensors is operational, but misbehaving. The wires to them might even be swapped so the Motronic is making its calculations thinking the outlet temperature is really the inlet temperature and vice-versa! I wonder if such a thing is possible?

    Re: 997C2S exhaust, 1 side more "contaminated" see

    soV said:
    Hi MMD,

    Thanks for your reply. Can you say a little more about your oil consumption when you had your 997 C2S (with the similar issue).

    What did your dealer/mechanic have to say about it?

    Was it the same discoloration, and at what intervals did it seem to come back?

    Thanks so much, Pete

    No problem Buddy, here goes:

    According to my accurate notes, oil consumption was exactly (LOL) one quart per 1100 miles for the first 3000 miles on the new car.

    I noticed the problem weeks after delivery of car. About a month later I brought it in whereafter the dealer service mechanics seemed slightly freaked out and hush hush. Didn't want to say anything, said they did not know what it was. Eventually told me to just drive the car and get back to them at next service which I took to be fked up BS (sorry for swearing). Mine was a 2006 unit early in the production run of the S engine (oct 2005?).

    Quickness of discoloration recurrence was unlike yours apparently, I'd clean them, drive 150 miles, and they'd be messed up again.

    BTW, verrrry upsetting to me to think Porsche would let something like this uneven soot happen and leave me hanging. Especially after my two year old BoxsterS got an RMS leak a few months before all this started with the brand new 997s.


    Re: 997C2S exhaust, 1 side more "contaminated" see

    Most 911s do consume oil. It is not unusual to see 1 quart every 800 miles...
    Some cars do not consume oil. Mine never did. Is it the way people drive? is it the luck of the draw? or both?

    Different burning on one bank vs the other bank is a different question. As previous replies state it can be an exhaust cat/sensor issue or worse.

    Re: 997C2S exhaust, 1 side more "contaminated" see

    MMD, thanks again for the reply...

    Hmmmm, after reading most comments, I feel that it is probably Porsche Strategy to declare this to be not abnormal....

    I am also surprised by the 'spread' of differences in the findings, meaning "Yes soot, No soot", and "Yes oil use, No oil use" and almost anything in between. I would have guessed Porsche would have built their engines within tighter production tolerances (or is driving/breaking in, such a big factor?).

    In the end of the day, I am not only a little surprised by this, but also a little disappointed, and I for sure understand your comments about Porsche who left you hanging.

    I have to say though, that until now, every time I drive the car, I have not been able to wipe the smile of my face for hours.......

    well, I'll keep monitoring, and if anything changes, I'll update.

    Thanks, Pete



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