Oil dripping out of exhaust pipe after AOS replacement?

Here is one I haven�t seen in my searching. backstory and video. 2001 3.4 103k miles Belt tensioner let go while on highway 2 months ago. Had it towed to shop, tensioner was replaced, belt replaced, transmission mount replaced, AOS replaced all at the same time while there. They did not drop the engine to replace the AOS and the part was not in a box or bag because it came with the car when I got it. Shop had the car for a little over a week. After it left the shop, I took it straight to the detailer for a full paint correction and a few other things. It sat there for 5 weeks total getting a cosmetic restoration and I just picked it up this week. I drove it properly to make sure it�s fully warmed up. Had some smoke out of the left tailpipe on startup but that has been pretty normal. Always had a bit of noise from the engine as well. Going down a longer hill at 45mph in third gear and letting the engine slow me down until I have to make a turn is where this starts. I made the turn and rolled into the throttle and had a large visible blue cloud behind my left flank. came home, parked it a few hours then made a video that I have to figure out how to upload. I�m seeing a small puddle of oil under the left tailpipe and the engine makes a distinct ticking noise. Any insight on what may cause that much oil to come out an exhaust pipe? My thoughts are faulty replacement AOS that is stuck open, bore score, valve seals or a combo thereof.

check your oil level first, it may be overfilled...

Yikes! The fact that your car was at two different shops for a long time is suspect. Who took it for a test drive?

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I was going to ask if he happened to check the mileage before and after the 5 weeks at the detailer.

How long have you had the car (miles drive ) before you had the belt tensioner replaced and AOS??

The belt tensioner was bound to break so that was no issue nor did I particularly care that it did. it had less than .2 miles added on those 5 weeks. For note, this detailer has been my guy for years and does impeccable work. He had to start it a few times to move it around within the shop.

How long have you owned this car? This does not sound good. I mean, I actually don�t know what it sounds like - I don�t see the video? But I mean a ticking sound and oil inside a tailpipe with smoke. Something is leaking oil into the combustion chamber. Check oil level, cold, after car sat for 8 hours or more, on a flat surface. If that�s good (not above full mark), you�ll have to start investigating. Most 996 engines that tick have bore scoring, a loose spark plug, a loose exhaust header, a bad cat, or a bad injector, or a coolant hose that�s smacking the body. I don�t think any of those relate to oil out the tailpipe except bore scoring or a faulty AOS. I would also check your coolant to make sure there�s no oil in there. Also, how long did the engine run after the belt came off? If it was a few mins, heat could have caused damage to the engine. If you pulled over immediately, shut off the engine, and had it towed, you are probably fine.

The oil leaking could be the engine mount and not related to the smoke. Maybe not likely but worth checking.

From what you say, your smoking most likely indicates a problem with your aos. But I question oil actually dripping out of the exhaust tips? It would have long since burned as flames and a cloud of smoke out the tailpipe. But anything could happen. If you are not mechanically inclined, I would get the car into a good Indy shop so they can fully investigate and address the issue. Regardless of what the issue actually is, and since the shop will be playing around with your AOS anyway, you may want to consider splurging for a UAOS set-up for the long-term and get rid of the crappy and frail Oem aos. Did I say crappy and frail? Yeah I did. It was the first "factory" part that I got rid of on my car after failure in 2006. Why, because flames, smoke clouds and ultimately engine failure can and will occur. Your Indy can figure out what the problem is. Just get one that specializes in P-cars.

Do a vacuum test on the oil filler to be sure the AOS is okay as a first step. Easy and quick to do.

I spoke with my mechanic and have an update. He is a p-car mechanic, as this is my second Porsche. I normally just drop it off at the dealer and have them figure it out and I might do that with this issue if it�s not solved here in a few days. To answer the other questions, I�ve had this car a while. It gets driven all the time ~10,000 miles per year. None of the oil analysis samples have shown any metal or silicone. When the tensioner went, I was able to pull it off the road, turn it off, and waited for the tow straight to the shop. The temperature gauge never went above 180-190. The mechanic filled the oil after the work was done and may have over filled it. Additionally, he said the �oil� out of the tailpipe may just be condensation coupled with carbon in the exhaust and he would have to check it again. He agreed to do a bore scope to confirm his suspicions that it�s just overfilled and not actually an issue. I�m going to check the oil level here in a few minutes because it�s been sitting for a couple days on level ground while the snow comes.

If the so-called oil out the tailpipe is black, then I agree, it�s not oil, since oil was just changed. Fresh oil isn�t black.

Checked oil level. Within normal range. I�ll be taking the car back to the mechanic this week

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Good to hear you are on top of it and your Indy will get to the bottom of it! please let us know what you find. We can all learn from it!

Is there a way to attach a 140 second long video to this thread? Every time I try, it says the file is too big. Even my photos are too big as they can only be 10mb.

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I had to create a YouTube account and then link video. that doesn�t look right. Only drivers side? maybe as mentioned, it�s just condensation�.

It�s only on the drivers side yes.

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A couple of thoughts.. Why was the AOS replaced in the first place? Was there some symptoms ie. smoke coming from both tailpipes. Because considering what was done it's not a "while in there" type of job. It's a major operation when the engine is in place. Another thing - is the new AOS itself a genuine Porsche part or some el cheapo aftermarket thing - I've seen both and there could be a night and day difference in quality even the price is not that far apart - aftermarket AOSs are here in EU between 80-160 euros and genuine Porsche 190. There are also reports that some of those are broken out of the box so that is a real possibility. Unfortunately sounds probably a potential bore scoring if that had been pretty normal previously - along with noise from the engine. One of the problems with failing AOS is that it can mask other issues - esp. bore scoring because when AOS is broken you'll usually get excessive amount of smoke coming from both tailpipes. That conveniently masks of course bore scoring which is pushing at the same time only from the left that cannot be seen behind that AOS smoke. Another thing is that failing AOS is pushing a lot of oil to the exhaust and it may take a while before all that is burned from the muffler etc. Bore scoring + head gasket btw. did you check that AOS to crankcase breather vent valve that is on the bank 2. Mine was really dirty after failed AOS - not sure what would happen if that were completely blocked? Could it cause some oil/smoke from the left tail pipe in that case?

Excellent questions! I had the AOS replaced because there was more smoke from the exhaust than I wanted. Figured it would be a smart choice as the Boxster I had before this was an issue and always threw codes. So it was a bit preventative. Genuine part though. After it gets borescoped this week I will update this thread. I�ve already begun looking into the resleeve and upping the displacement but if I can avoid that, I�d be happier.

Have you checked you vacuum level of the engine to verify that the new AOS is working properly? I installed a new AOS on mine to fine the new part was faulty. I don't think that is probable but it does happen.

I may have jumped the gun here. I allowed it to warm up to full temp today before moving it. Only water out of the tailpipe. Will check again when I get home.

I was going to say, that picture of the �oil� didn�t look like oil. Yea!

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That's more like it - if it were dripping that much oil it would be smoking like a WW2 dogfight victim.

Dave, A failed AOS could be your issue. Have a manometer test done. Take the throttle body off and look for oil in the right side intake runners. Oil can pool up and when you turn left it gets down into the head and smokes out the left side tail pipe.

Update, Not oil from tailpipe. I do, however, have piston slap. Options are; - regular rebuild - rebuild and upgrade to more displacement - swap engine with one already done really not sure which way I will go.

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Dave, sorry to hear the news. You have plenty of choices. Comes down to if the car is a keeper, what you are going to use it for (street or track), and obviously financial timing. Imho, you can't get a better 911 than the 996. To me it's a keeper. But what I think doesn't matter. Assuming you can find a swap engine that's already been rebuilt, or you go with one of your two other options listed above, you will be starting with a brand new engine, which means that with all we know now about preventing bore score and improving overall engine durability thru the proper servicing and parts, seems to me that you will have another couple decades of worry free fun.

A fourth option is to live with bore scoring until you made a decision. How bad is it? Did you have the cylinder bores scoped top to bottom?

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I will revive this for a proper update. bore scoring confirmed. new motor gets installed in two weeks. Right in time for spring top down season!

Bummer news on your engine, but you sound positive about the whole ordeal so good on you!

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Dave which engine is the one going in? Where you got it, and would you mind telling is the cost of the engine? Glad that you will be able to drive in a few weeks. My car has been at the mechanic for the soul headers install (6 broken header bolts) almost 2 weeks and I have been missing it, since I try to drive it twice a week.

So, the �mechanic� said and did nothing until he was asked/told by the customer to scope the cylinders�??? Now he�s replacing the engine?😳� WOW!

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I couldn�t agree with you more. I sold motor oil, gear oil, coolants, to garages and car dealers all over the world, it�s crazy what they would do. On my personal cars I had two bad experiences charging me for replaced parts that were never installed. Anyway when I got into this Porsche world I visited 5 shops and I also got all of them to quote me the difficult AOS replacement. Two of the shops higher in cost than Porsche dealer. Two other shops I didn�t felt safe leaving my car with them, and one of them never quoted the job. Last one best quote and it also included replacing the serpentine belt. Anyway then I found my mechanic thru Tex squirrel 🐿, I trust this guy, will be willing to become a financial partner with him and no worries leaving my car there. We understand each other. Anyway he works three days a week for the best of the 5 shops I visited. When I need something done if it can be accomplished in a day, I just go there to his house and back, I just want to know learn as much as possible about these cars. He doesn�t mind if I provide the parts but I give him a chance if he can get them at a reasonable price so that he continues to build his accounts. I�m turning 54, he�s 33 so I feel good supporting, helping someone that will be the future, I could wrench some but I want him to succeed and prosper.

Maybe he�ll let you pay him in brisket & ribs! 😜

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yes everyday I�m out there I make sure everyone eats good. Got some 6 ounce Wagyu chuck brisket burgers and some jhonsonville beddar cheddar sausages for the menu on Monday. I may get a slight discount but I still pay. Need to get the Houston area guys to get together, we could go out there on a Sunday and have a cool get together with food and drinks, he kinda of live out there but he has land. My house lot is only 65 by 150, he probably has at least 1.5 acres.

Getting �new� motor out of a wrecked car that has been checked out and refurbished. Has half the miles of my car. $12,000 plus core and install costs. I�ll have it back in two weeks with a new motor and new convertible top. It is a new mechanic. The company I am buying the motor from will be doing the install as a full cradle swap at my request. It�s the same 3.4 motor that is in my car.

^^^Good luck with �er ! 👍