White smoke / metallic smell

I think I have a major problem. About a mile from home I was under full acceleration, not near redline and looked behind me to see a nice white cloud of smoke. I immediately backed off and basically idled it back home. It stopped smoking unless I accelerated. There is a new metallic smell I am noticing. No fluids on ground under car or loss of oil. Don't want to start in case it makes it worse. Anything to check, or should I just get it towed to the shop. #FML, just got it back the other day.

A little more back story. The shop disassembled the left bank (1-3) to diagnose a misfire issue last week. Could this be a problem with the work they did? I worry that even if they diagnose the problem and they caused it that they will make something up to cover their ***'s. Yeah, I'm paranoid, but been screwed before.... Any words of advice here is appreciated.

Flatbed your car to a DIFFERENT SHOP. Best of luck. P.S. Hope it's just a bad AOS

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+1 I lost faith in that shop over 10 years ago. Have you tried these guys? Outside of Chris Schuh, O'reilly has a good rep too. http://www.oreillymotors.com/porsche/

Oreilly is on the short list, but in Madison and I am near Milwaukee. As for the problem, since the smoking stopped I am leading towards a clutch disc disintegrating. I've blown engines before and this smell more reminded me of clutch material. Maybe the front differential exploded? Cars at the shop... Prob be a few days before I hear from them.

Can you tell which exhaust pipe(s) the smoke came out of? Could be just a blown AOS.

Could just be overfilled oil, too. Check the oil level.

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To start with if the smoking is from something the shop did or didn't do you won't help your position by taking it another shop. The 1st shop will argue you should have brought the car back to give it the opportunity to address something it might have done. 'course, if you don't trust the 1st shop possibly having to pay for its mistake out of your pocket at another shop could be the lesser of two evils. Depends upon how bad the situation is. I don't think the smoking is from the clutch or a blown front diff. One possible explanation is the AOS failed. Another possible explanation is -- since the head was off -- this opens up the possibility the camshaft cover on that head having sprung a leak. I am ignoring a possible head gasket leak as there is no CEL. The camshaft cover leaks -- if it leaks at all -- under hard acceleration as the crankcase pressure builds and thus forces the oil out between the cover and the head or out around a bolt. There are a number of spark plug tubes that could leak too. Even though the engine is not manifesting any abnormal behavior, other than the smoking, my advice is to err on the side of caution and have the car flat bedded to your shop of choice to have the source of this smoking ID'd and addressed.

Car was flat bedded to Mraz yesterday afternoon. Hoping to hear something today. Fingers crossed!

So, why was 1-3 disassembled? What was the issue?

It was random misfires only on bank 1, diagnosed as bad cam solenoid seal (didn't say whether it's the timing one or the variocam one). Bank 1 cam cover was removed and resealed, valve train checked. https://rennlist.com/forums/996-foru...p302-p303.html

Ok, bare with me. Engine still runs. Shop bore scoped all cylinders looking for scoring or d-chunk. No physical signs of either. However, there was a small amount of oil and liquid in cylinders 2, 5 and 6. They pressurized the system overnight and found some liquid on the outside of block. Not really sure if it's a head gasket or possibly the crankcase pcv system. I know its called something else, but can't remember. Also, didn't see any cracks on the block/cylinder or anything. If you have something constructive to share with the shop please share. Should here more tomorrow.

The external leakage does sound like a head gasket to me. I have seen only two head gaskets fail and both had external leakage. Approach with great care.

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While I might be willing to blame a head gasket if the fluids were all limited to one bank and to the bank recently opened up, unless both gaskets have failed and in several places my opinion is the AOS is the culprit. Its failure can have not only oil but coolant in the engine, and in more than just one or two cylinders. Regardless, avoid running the engine any and get the car flat bedded to a shop that can ID the true source of the symptoms.

Its not adding up, the more I think about it... I smell an underlying condition.

What is the best route to detect a head gasket failure? Can we pressurize from the spark plug tube and watch for bubbling in the coolant expansion tank? What would this prove or could I be getting false results being this could be a cracked cylinder. Reason I'm asking is the tech pressurized the system again and only found coolant in cylinder 4. Appears the problem is near. Next step should be removing the engine And inspecting head gasket right? I have the shop putting together estimates before yanking the motor on possible outcomes.

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If you have the right shop the shop should tell you what the next step is. If a bad head gasket is suspected a leak down test of at least the suspected cylinder and probably the cylinder on either side is what is called for if not all 6 cylinders. You don't want to assume a head gasket leak will cause bubbles in the coolant tank. That's a long way away from the head gasket. I would be inclined to drain the cooling system before leak down test. If there is leak in the gasket between the cooling system and the cylinder/head I want the air in the cylinder to leak out with as little interference or resistance so the pressure in the bad cylinder drops and clearly signals there is a leak. With the cooling system empty then you can listen at the coolant tank for any sounds of escaping air.

Update! Well, the shop wanted to drop the engine and disassemble and look at the block. I asked them to hold off since I wasn't comfortable they were on the right path. After speaking with Jake and a few other AWESOME shops about a possible rebuild they mostly thought that this had something to do with the AOS. So, I advised my shop to take the intake off and look for oil, but instead they ran another pressure test and found that pressure was being allowed back into the crankcase. They ran the same test on another 996 in the shop and it didn't leak at all. This lead them to the diagnosis that the AOS is bad. So, I dropped my new AOS, thermostat and water pump off and said install them...crossing my fingers in hopes it all ends here.

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You asked the shop to remove the intake and check for oil and instead it did another pressure test? And then you are relying on this shop to further work on the car? I'd seriously consider finding another shop. While I hope the problem is AOS related I'm having a hard time coming up with a way that pressure in the cylinders can make it into the crankcase via a bad AOS. The AOS is connected to the crankcase and the intake. It has no responsibility for maintaining pressure in the cylinders. Certainly if there is a pressure leak in one or more cylinders air flow/sounds might be at the AOS as this is the only path for air inside the crankcase to make it to atmosphere as the air flows through the AOS to the intake manifold. To put it another way: If one or cylinders are pressurized and pressure drops there is a leak in the cylinder, or head, or around the valves, or past/through a compromised head gasket. If the engine was just overreved I'd guess bent valves but in this case I'm more inclined to believe a cracked head is the culprit. As it has been reported here and backed up by the distinct lack of posts on this failure mode head gasket failure is a rare event. But the AOS/water pump/T-stat job is already underway I guess. Let's see how this works out.

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Macster, I wish I knew. While I understand this reasoning I am an amateur at best. The shop is doing all this work for a few hours, so the bill is low. Replacing the AOS will eliminate at least one possible cause. Once the old AOS is removed is there a way to inspect it or test to see if it was bad?

Alright, glory is mine at last. My baby is back in the garage running like a champ. Turned out only to be a bad AOS. All this confusion mostly to do with my mechanic not be familiar enough with the m96. Seriously, I asked about the AOS a long time ago and he was set on d-chunking or cracked cylinder. So another grand to install the new AOS and I'm back in the road with a little less cash, better than a new engine. When I picked it up it blew very little smoke and since then no more. Idles perfectly and sounds great. I'm in love again! Thank you everyone!

Glad you are up and running. The shop knew exactly what they were doing...now is the time to find a new mechanic.

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Goes without saying, right?! I ran into two other 996 owners the first day back on the road and it was odd, but both recommended a Porsche master tech at Reina Auto in Milwaukee. I test drove a 40th Anniversary with them a while back and they were great to work with. Might give them a shot.

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Had a similar experience at Mraz when I took my C2 in for the IMS and RMS. They kept pushing this "d-chunking" phenomenon I had never heard of instead of all the common issues I'd read about on this forum. That being said, they did a great job on the work. Glad to hear you're back up and running, it's definitely been a hard luck summer for you. And I'm jealous you got to drive that 40th anniversary at Reina, it didn't last long. I'd been meaning to go take a peek at that violet chroma flair paint and before I knew it, it was gone.

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Reina on Capital Drive in Brookfield. I have a few cars from them in the past. That's where I got the BMW 2002 from. Joe Reina is a decent guy. I actually grew about a mile away. A little bit of irony......Mraz and Reina used to share space at that building before Mraz went to Pewaukee. Good luck!

Might take the 996 to Reina now. It's been about 500 miles since I had the AOS replaced and this morning KITT decided to lay down a smoke screen. I was under hard acceleration taking a long sweeping turn through an industrial park at about 40-60mph. Which tells me it's nothing major, likely leftover oil from AOS swap and a ****ty job cleaning my intake out...maybe. Engine sounded fine and everything else checked out. I think there may be a larger issue or possibly a little leftover oil sitting in the engine went into the intake. My only reservation is that when this problem came up prior to the new AOS it exhibited the same behavior, to a "T." Now this could be a number of other items. Thoughts?

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How's the oil level and do you have a manometer to check the AOS? Even a btand new unit can fail out of the box....ask me how I know.

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I think I'll pick one up today from the science store and see what I get. thanks!

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Ok, if you're getting those U-shape tube ones filled with liquid, I suggest filling it with engine oil instead and multiply your reading by 0.9 to get the reading in inch H2O (should be around 5" H2O)....in case you engine sucks the liquid into it due to excessive vacuum.

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Either get the same one as Ahsai or I(Pyle digital manometer) or you can just make your own. No need to go buy a liquid version.

Yeah, funny you mention this. I will make one with some spare tubing, etc... However, if I make my own how do I know what a baseline reading is vs a high reading? I may just go to my buddies shop and use his digital one.

Already told you in post #29 "should be around 5" H2O" When they fail, you'll see 10" H2O or higher.

I looked in the intake and it was glistening with oil. FML, either a bad AOS or the shady shop didn't even replace it. Once I pull it out I will know for sure. It was a genuine Porsche part too. Anyways, see attached pic. I'll also make a manometer tonight and check it out. #996moneypit2016

The oil can also be from the OLD AOS that the shop didn't take the time to clean out. The intake manifold could hold quite a puddle, especially at where it branches off to the three cylinders. My guess is your new AOS is fine and the oil is just left over that needs to be cleaned up. But yea, best to use a manometer to confirm that.

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Right on, I'll give it a try. Thank you!

Here are some readings with my homemade manometer Basline Each line is .5 inches

Looks very close to 5" H2O (The distance between the two water levels assuming that's what the liquid is). Perfect! I suspect it's just residual oil puddle in the intake from the old failed AOS. Maybe just clean it up and keep driving and monitoring it?

Judging from the small increase in pressure and reading other AOS threads this is a "normal" reading? Wish I took a baseline before I had the AOS replaced. Fresh oil in intake, new AOS and normal pressure...what's next.

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Heading out of town for a bit, but I'll Remove the intake and clean it out good along with some good pics. Thanks!

See the deep dish design of the manifold? Could easily hold a quart of oil image.jpeg

So, I took the plenum off and inspected both intake manifolds. There was no oil in the manifold with the exception of a little oil residue and a small puddle right off the plenum. I did notice a lot of oil build up around the outside of the plenum and gasket on the left. I did confirm the AOS was the new one judging by how clean it was in comparison to the rest of the engine. Cleaned and wiped everything down so if I get new oil I know something else is going on. Crossing fingers.