Cause of oil in cylinder 1

I am trying to determine the cause of a small amount of oil resting in the bottom of cylinder 1. Background: Car- 2000 991.1 c4 cab. 6-spd manual with 77,000 miles. I have owned the car for about 7 months and have not driven it much. The prior owner had the car for 2 years and drove it daily, and frequently changed the oil (Liquid Moly 5w-40). I had planned to do an engine-out maintenance in the near future but I did a cam deviation test (Bank 1 = -9.39, Bank 2 = -4.13) and since it was out of spec I decided to drop the engine now and replace the vairo cam chain guide rails, as well as do the IMS, RMS, etc. With the engine out and the plugs removed I checked each cylinder with a endoscope. I found cylinder 1 to have a small amount of oil and traces of dark particles (They matched the ones I found in the oil filter that I assumed was from the chain guides wearing). I also noticed a dark line on the cylinder on the bottom near the oil puddle (scoring ?) I also saw a similar line at the top of cylinder 6. There was no oil in any other cylinders. The other thing I saw wen removing the engine was some oil on the inside of the right side of the plastic intake air plenum behind the metal throttle body. There was also a puddle of oil directly beneath this area on the top of the engine. Ca anyone explain wha t's going on? Can I provide any more information?

I would test the AOS and most importantly Test the engine health/blow-by https://rennlist.com/forums/996-foru...hlight=blow-by Oil can only get tin the cylinders through the intake/AOS , from the valve guides ( not likely since the engine lays flat), or seep past the rings which is very likely due to several reasons.. 1;; the engine lays flat and the rings are modern low tension. 2 the rings don't seal well when just sitting, the compression in operation actally helps the rings seal.. 3 the cylinders tend to go oval over time which may or may not effect the ring seal ( blow-by test to verify the degree of health)...

Change your AOS (air oil separator) in the next 250 miles. I am speaking from experience and am sure it is your air oil separator on its way out. If you wait, it will fail completely and suck more oil into your cylinders and you will hydrolock it with oil. The aos was designed for environmental reasons. Its purpose is to collect residual gasses/vapors from the crankcase and reroute them back through the intake manifold. The gasses are then burnt off in the combustion chamber as a result, making tree huggers happy. When the diaphram fails, oil makes its way into the intake manifold thru that hose on the 10 o'clock position on your throttle body. It gets worse and worse obviously and I've found there is much misinformation on the "leading up to" faults with the aos. If you are a diy guy, I promise you it is an easy job and people complicate it more than ever. The key is to look just above the alternator under bank 1's intake manifold, while you take a pair of pliers and literally snap off the coolant hose connectors to the current aos. You will see how it works and you will always be able to pull the snapped ends out of the hoses, as they almost always break in the same place and leave enough to pull out with pliers. The first time I did mine, it took me 2 and a half hours. A shop will quote you $1.5-2k and 8 hours of work. I am telling you it can be done in under 3 and that's being generous. The hardest part is getting the frontmost intake plenum back in without removing either intake manifold. Hope this helps, best of luck. Oh and people say buy the genuine aos, but the reality is Vaico makes the genuine aos, so just buy the Vaico unit if you want to save some money. To each their own.

Vaico doesn't make the OEM AOS...Mann+ Hummel does...your other statements have assumptions also..

Quotes source post: 19718997

pt just because I don�t promote your uaos in every post I make doesn�t mean I�m wrong. I am correct, and I am correct because he mentioned oil in the intake manifold as well.

How certain are you that Vaico is the OE manufacturer of the AOS? I don�t think they are OEM for anything.

Quotes source post: 19719032

I don't know why you don't , you know it is the best solution to a 20 year problem that has been plaguing the M96 since it was built..and you know that a failed one can lead to catastrofic damage, you have even said so your self on many AOS/smoking threads...and you know how often they fail.. But you probably don't know the many other benifits of the UAOS System.. But I know you won't promote it, and thats ok, and I know why, you don't like Porsche Dealerships, or even Indys, or Professional Porsche Techs... But like I said Vaico doesn't make the OEM Porsche AOS....Mann+Hummel does......

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I was informed that Vaico makes the oe aos directly from the owner of flat edge autoworks in Bluffton, SC. Admittedly I have done no research of my own on it, I just took him for his word. I�m sure you would too. He�s well respected in the community. pt- stop nitpicking everything I post on these boards. You are not the master of all here. I get defensive because the amount of misinformation ya�ll spew out of your mouths. It is utterly insane. Your uaos is a great product�there�happy dude? Op if you�re a diy guy and want to save a couple hundred dollars, replace it with a stock aos using my tips above and you�ll be good - most likely - for another 50-100k miles. Do as you please.

I let a lot of the BS slide on the Internet,... because , well it's the internet and everyone has an opinion but sometimes just have to straighten something out... PS :: Oh, I forgot to pic on you in the last post...

Are you still driving the car with those cam deviation numbers? If so I wouldn't recommend it. Mine is in now for chain guide replacement (I had reading of 4 on the left & 6 on the right) and was told I was living on the edge with those numbers. by several different shops.....

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This is actually more accurate than you know. I replaced a brand new AOS for someone and it only had 50 miles on it when it failed. It had been replaced by the owner with a Porsche AOS. It was warrantied by FCP, but the owner didn't want to go through the work a second time.

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I highly doubt this to be true. You probably didn�t seat the bellows tube correctly. It doesn�t fail in 50 miles.

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Lol and yes I did feel like that because I did it in a way that no one has ever documented, and in a way that will save people lots of time and money.

Quotes source posts: 19720312, 19720409, 19720427

Exactly !! And many many more cases the same or even worse...... You can doubt it all you want with your anedoctal opinion , but the fact is there is many many documented cases right here in this forum of AOS's failing right out of the box, and some cases of people having failures in consecutive years ( like 3 years and 3 AOS failures) ... The Factory design is frail, and even more so people don't realize how the deficiencies effect many othe things on the engines ..... The AOS is the most failure prone part on the M96/7 engines ...... There is a Thread here you can post your procedure if it is all that great and wonderfull.. https://rennlist.com/forums/996-foru...+tricks..There is many Tips and Tricks and proceedues here and many that have not been posted, but IMHO the install is very straightforward and should not be difficult if you are mechanically inclined and handy with a wrench...

Ug. I just have to comment. Sorry op for the mess this has become. The AOS isn't thin and frail. I know because I murdered one with a hammer and a flathead to see what was inside. What part of the rubber, or the spring inside the diaphragm is thin and frail? It is still my humble opinion that the AOS fails because the rubber bellows tube cracks, causing a leak. And before anyone knows it, the AOS goes along with it. That is why you see oil dripping from that area - it's coming out of your cracked bellows tube. Oh and the crack usually develops on the part that is most flexed, which is on the side that you cannot see from under the car. My procedure is great and wonderful and it is a great and wonderful alternative to your piece of **** product that I will never put on my car.

Quotes source post: 19721786

You just don't know what you don't know...... I'll only entertain you for a little longer...I know you are just after attention and not spewing all this misinformation on purpose... The diaphragm on the AOS is 95% the cause of AOS failure and has failed in Tens OF Thousands of M96/7 engines....!!! The thickness of the AOS is measured and shown here www.ultimateaos.com on the FAQ page .. along with the twice as thick UAOS diaphragm ... Yes there has been "Tens of Thousands" of AOS failures and only 1k of the UAOS's installed in the last 3 years , but is growing every day despite people like you who deny the issue...But that's ok, I have abandoned visions of grandeur of saving them all and am satisfied with just saving the ones I can from this failure, and upgrading for increased performance and durability...I'm old and Retired and not really interested in the work of saving them all......The ones like you who are ok with the risk because they drive around like a Grandmaw will be ok without the UAOS System .and just replacing it every so often.....

Quotes source post: 19721786

I bet you are a great and wonderful guy as well. But stop with the drama. You are an emotional basket case. Get yourself under control and learn to have a reasonable discussion.

Quotes source post: 19719081

I don't think a (independent) shop owner per se is a reliable source for the knowledge which company supplies an OEM with parts. Vaico is a brand of Vierol AG. On their homepage Vierol states We are a specialist in international independent parts trade. Says it all, really . Source: https://www.vierol.de/en/automotive-division-2/ On another note, I believe the two of you agree on more aspects of the AOS than you disagree on. Perhaps it's worthwhile to consider that and give each other some space to rate the design of the AOS differently whilst avoiding to take dismissal of arguments put forward as a doubt of one's experience and knowledge. Bloody hard with only written text, I know but worth it.

UPDATE - First, thank you all for your informative comments. I have learned much from them and from other posts on this subject. I now believe that I may have been the cause of this problem by over filling the oil. Earlier this year, a few months after purchasing the car, I added a quart of oil. In the following months i rechecked the oil level and discovered I had added about a half quart too much. During this time I had driven the car about 400 to 450 miles. Upon discovering this I removed the extra oil. I have driven the car about 50 miles since then and now have the engine removed. With the engine out I have noticed a lot of oil residue covering the AOS as well as the area where the tube from the AOS enters the engine over cylinder 4. In any case I plan the replace the AOS as part of my engine out maintenance project. Comments?

I would (and did) install the UAOS. At the very least, if the diaphram fails, it is easy to change on the UAOS. The rest of the parts don�t fail, except for old pipes. I have 10k miles on mine now with no issues running the sump over full (9qts).

Quotes source post: 19722476

Glad you figured it out. Yeah, you just described the most frustrating shortcoming of the factory AOS,which is its inability to process oil effectively if you (1) accidentally over fill it, (2) park it on a hill, (3) decide to drive the car on some fun rolling and curvey roads. It will smoke, even if it hasn't failed. Replace it with the UAOS Track, even if you dont track your car because yiu can overfill the oil by 1-2 quarts without worry. Further, you can park it on a hill as well as find any twisty road you want and it can handle it. Not to mention by design that the UAOS eliminates coolant lines going thru the AOS so you mitigate the risk of intermix. In addition, the diaphram is 2x the thickness of the oem AOS and Motorsports AOS which adds to its durability. Lastly, the diaphram sits right on top and in front of the engine, which means you can replace it in under 5 min in case it fails. No need to lower the engine or perform acrobatics again behind the engine to change it. Kinda a no brainer for those that think it thru.

Quotes source post: 19721970

Look man I get you have this business and you make money from a product you've designed and sold. But I'm not going to sit here and get told that what I'm bringing to the table is invalid. The reality is: - an AOS costs $100 or $150 depending on if you go Vaico or OE > your systems cost either $710 + $30 shipping or $1,050 + $30 shipping. This does not include your other add-on's like fittings or the auto drains (which seem to be great add-on's). - my procedure for replacing an AOS takes 2-3 hours, because I have figured out a way to do it and am documenting that. Once you get good at it, it will take you and hour and a half, maybe 2 tops. > Let's say you go Vaico - that's a $100 investment in your car, and you get to know your car a little more by doing the work yourself. - your fear-mongering about the AOS being faulty as-is is simply incorrect. > the problem lies in the misinformation getting spewn around about how to tell when the AOS is going bad in the early stages. > the truth is, if you catch it early enough and you know the signs (spoiler alert - the oil cap thing is about the dumbest way to diagnose a faulty AOS - you are well gone if you're there) none of this becomes an issue.

Quotes source post: 19722476

Yes that is your bellows tube (though I'm a little lost when you say cylinder 4) and it is almost impossible to replace without pulling the AOS as a unit. I did it once but only with hose clamps and learned 20 miles later that hose clamps aren't what you want. You can try...Just buy the snap rings that are pre-set with the blue clamps. If you search, I believe Jeeper has posted the part number on an AOS thread somewhere. If you have any questions about the removal, PM me. Edit - though again want to be clear that you need to change your AOS now. Whether you go with PT's unit or a regular unit is up to you.

Quotes source post: 19722065

Relax pal. Just because I bring a differing view to this issue and have done more wrenching on my car than you've ever thought about doing, doesn't mean I'm "out of control" - the fear-mongering on these boards is what's out of control. I am the first person to say these are great cars and the two biggest issues that plague the 996 are nothing other than fear-mongering and misdiagnosis. That said I will be the first to admit when I'm wrong (as I've already done with the Vaico claim earlier - I will ask Patrick about that (the owner)), and be the first to admit that I don't know what caused the crack on my car's bank 1 head. I have read about the AOS causing intermix and I find it unlikely to be the cause of mine (I have written about it and chalked it up to owner negligence prior to mine). If the AOS is really that bad I simply don't understand why Porsche wouldn't have issued a recall, the same way BMW issued a recall on their rod bearings for e46 M3's pre 2003.5, for example. Or maybe the evidence there is in the different AOS design on the early 2000's cars, but I don't know anything about that or why it's different (serious) so won't comment. I know it's a 3.6 obviously but haven't researched anything on it. edit- and yes, I clapped back at PT because he was being a condescending d*uche, and seems to do that whenever someone else offers an alternative to his aos. If you notice he doesn't comment on anything else I posted (if you read my first post I give you the tips that will cut AOS install in half). It is very simple and there are no "acrobatics" that are performed in the removal or install, as you have just stated above. Again, spreading more misinformation and fear-mongering about the DIY aos job as-is.

Look Man, you are way out in left field......to prove to yourself just do an advanced search in the 996 forum for "AOS Failure" and you will see about 5000 full threads of this subject....This is the 996 Community crying for help, it is not me "fear mongering" it is from the 996 Community.. Then do the same search except on any other model , you will find zero or maybe less than a dozen on some models... It is not me "just trying to make a buck" or 'fear mongering"....and it really pisses me off to hear someone say this.......The Community cried for help, and I answered the call to develop a product that fixes the issue and also adds dependability to the engine to stave off oil starvation, along with saving money in repairs.. Most owners don't DIY and would have to pay up to 10 hours shop labor to replace the AOS . I recomend the charge be 4 hours but I have no control over what these shop owners charge... How much does Patrick at Edge Motorworks charge for AOS replacement on 996? Replacing the AOS every few years would get expensive for most owners and the UAOS eliminates this ( with many other benifits)... Maybe you should go to work for Partick installing AOS's and help the Community that way...because your advice is detrimental.. And again, you and Partrick are wrong on the Vieco being the OEM maker of Porsche AOS.s It is Mann+Hummel, they also make the Porsche Motorsports AOS and it uses the same frail diaphragm in the same hard to access location..( and has a very detrimental design flaw that holds over 1/2 qt oil that is needed in the Sump)) The UAOs is Superior design and performance and durability and cost savings.....there is no downside that can be argued....

The only comment I'll take back is calling your uaos a piece of sh*t, because the reality is I don't think that, and I think what you've done for the community is awesome. And you know that. I've said it before. But you decide to chirp me and expect nothing in response other than "oh yeah, go with his uaos"...you completely dsiregard any and all input I have to offer that is entirely based on my own experience with my aos troubles. I figured out a way to install an aos in a very simple way. One that does not require any removal of the alternator, bank 1 intake manifold, or lowering of the motor. To be honest I have been lazy about making a formal writeup and part of me doesn't feel like dealing with the backlash I'll most likely get from people who just want to slam the uaos down other people's throats. I do not believe in the horror of the AOS being faulty by design, because there are countless people who have replaced their aos with a stock unit and been fine. That's the reality. I come along and say hey it can be done in a short amount of time and everything you thought you knew about the difficulties of doing the job yourself are essentially wrong, and I get the book thrown at me. And I've already commented on what I said about the Vaico unit. Read.

And these are the key takeaways from that DIY that I have yet to make (this diy does not include replacement of hard tubes that go to AOS): - unhook battery because you'll be near the starter. - remove everything from the airbox back to the frontmost intake plenum. - the only coolant hose you have to remove is the top one that goes to the coolant exp tank, because you'll see it hooks to the AOS and you need the room to feed your left arm/hand back there. - with the plenums out, crouch down and feed your right arm behind the intake manifold, while looking just above the alternator / under the intake manifold to get a clear view of coolant port #1. Take a pair of pliers and just snap that thing off. use fingers to pinch and pull hard tube #1 off. - do the same with coolant port #2 that sits atop the aos. Feed your left arm over the top of the manifold to get to this one. You will not have a view but it doesn't matter because you're going to snap that one off too. - pull hoses out and remove snapped ends. - get under car and undo variocam solenoid clip/push connector out of the way, remove bottom of bellows tube clamp, and undo the two 10mm bolts that bolt the aos to the block. use fingers to undo hard tube #2 - this will be a b*tch but it can be done. - feed AOS out from the top of the car thru the intake plenum area. install in reverse. To sum this charade up - these are the facts: - if you want to spend the money, go with pt's unit. It will more than likely save you - in my opinion - the *small* risk of the stock aos doing catastrophic damage to your car if the stock aos goes bad (think hydrolocking (PT's unit does not have coolant running thru AOS) or intermix caused by the stock aos (uaos diaphragm is more durable)). - if you don't want to spend the money, you will likely be fine replacing a bad aos with a new, genuine porsche aos unit. There are many cases of people having success with replacing a bad unit with a stock one. Yes it will probably fail again in 50-100K miles, but it is a $150 part. - if you want to try and replace it yourself and save the $1.5-2k you'll spend at a shop quoting you 8 hours of work, I have found a way to do it in under 2 hours. Dare I say an hour once you've done it before. The biggest time save is because you snap the coolant ports off with the hoses still attached, instead of trying to undo the clamps with needle nose pliars. Just break the ports off the thing - you're putting a new aos in anyway. Install is reverse. use hose clamps for the coolant lines and install the hose that goes to the exp tank to the top port of the aos before you feed the new aos back there. The biggest pain is getting the frontmost intake plenum back in the car because you'll deal with the starter getting in the way and the intake manifolds are still bolted in. Persist and you will succeed.

Quotes source post: 19722912

Originally Posted by GC996 I bet you are a great and wonderful guy as well. But stop with the drama. You are an emotional basket case. Get yourself under control and learn to have a reasonable discussion. Well said, GC996. I could not agree with you more. To his credit, Porschetech3 has offered considerable sound and respected advice for many years on this forum. To be called a d**che and other childish names is uncalled for. If hkovalcik were a fifth grader, he would be sent to the principal's office, ordered to sit in the corner with a bar of soap in his mouth. By the way, I use more foul language than anyone, but I do not call a guy a d**che without risking a fist in my face. No matter how effective hkovalcik's AOS replacement procedure might be, he has discredited himself on this forum.

Did you do the search for "AOS Failure" like I suggested ? IF SO there is no way you can accuse me of "fear mongering" and " just trying to shove UAOS down you throat"...All that 5000 Threads came from 996 owners and is only a small portion of the total 996 owners in the world... The anecdotal opinion of a few people do not mean anything in the big picture In reality these are $80K to $100k cars if they were built today or in pristine condition. Sure you can reduce them to 4 wheels and a running engine that goes from point A to point B, or anything in between.....And if that is your primary objective just say so,.......... but the UAOS System is far Superior and yes the Factory style AOS would be considered a "flawed design" and should not be used on any 996 that is cared for.. Again, there is no argument against the UAOS System that holds water, but there is plenty against using the factory style AOS... If you some great Tips &Tricks or a full procedure post it here https://rennlist.com/forums/996-foru...ht=tips+tricks it may help someone, the UAOS install is the same only 2 more screws 2 caps with clamps more than standard AOS install...

FFS. What a comical thread (and subforum) this is. I'm outta here

Wow! Ya can�t make this sh*t up! Skip makes some really good and useful products� You can use them or not - totally up to you.

Quotes source post: 19723271

Yea, I suppose a little dust up can't be avoided on a Technical Forum, but True Technology always Wins ...

Deleting everything I wrote in this post. If you're subscribed to it, you'll see it. Best of luck with everything PT and goodluck with the business.

See there !! I don't have to do any "fear mongering" , you are doing it !!!......and the 5000 owners who have done the same.... lol .. I just give Technical Info/facts. .... I really wish my bottom line was as good as you think it.....lol......I think you just put that out there in hopes people would be pissed at me for making "TONS of $$$" ...lol .......You would feel sorry for me if you saw my bank account....... The only real potential value in your diatribe is that you may be able to convince some people to DIY.. something I have been doing in this Forum for years.... See ya !!

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Can�t resist being a d*ck can you bro. You know what, I wish I kept up what I wrote. Tried to take the high ground but now I just think you�re an idiot.

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Oh DUDe....you should have left it !!!! . You said it !!!! BTW;; You were the first to be a D*ck...I just punch back......

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Quotes source post: 19720409

It was a 996.2, so no bellows tube. The owner installed it properly. It was faulty from the factory.

Quotes source post: 19723706

Ok, Ok you're right your install method is good and no problem for a DIY'er. However the downside to a failed AOS at speed is severe, so if there is a way to stop that from happening, for a resonable amount, why wouldn't you?

Quotes source post: 19724809

Agree with you Tex. I had two fail back to back in the mid 2000s. I was so PO'ed about the lack of durability and functionality that I went to the Porsche Motorsports AOS which at the time was the only available solution. But my Porsche Motorosports AOS failed a couple of years ago, and after studying the design and functionality of the UAOS and the development of the Track Drain and its benefits on both the street and track, it was a no brainer to upgrade to the UAOS. We are all trying to save money, but its important not to confuse how cheap the factory AOS is with the true overall cost associated with using it. As an owner of the same 996.2 for 22 years, I am well aware of the decision tree we all go thru and the cost/benefit of each decision over the long term. Been there, done that.

Quotes source post: 19724825

Fair point- if you are tracking your car, yes, go with the uaos. Porsche designing the motorsports aos is proof of this. The reality is the majority of stock genuine units aren’t bad out of the box. The reality is many people have replaced their faulty aos with a genuine unit and been fine. The reality is if you diy, you now have a way to do it in under 2 hours. The reality is if you catch the symptoms early - oil on ground, loud hiss in engine bay, and hovering idle around 1,000rpms or above - none of this becomes an issue for a daily driver, which mine was. The whole white smoke thing and oil cap thing only comes after it has completely failed and you are too far gone - two symptoms that people say you should look for on these boards. Incorrect and misinformed. You get to that point you are screwed. it is not the imsb (4% of single rows failed, 1% of dual rows - imo because of owner negligence around oil changes). It is not bore scoring (true bore scoring is rare). It is not the bits of plastic you find in your sump. It isn’t even the metal shavings you find in your oil filter. It isn’t your dumb oil analysis. It is not anything else other than your aos going bad that will have you looking at a 2-12k repair bill depending on if you source a used head or buy a used engine. I am spreading info on the facts - the facts on how to catch it early (because remember folks, these cars didn’t come with a Motorosports aos installed, so there is value in educating others appropriately), and how to change it yourself, and yes, with a genuine unit. Because again the majority of units are fine, and fine for everyday use. That is the truth. In 2021 I bought my car with 96k on it. In 2023 I drove it across the country from Philly > Bluffton, SC > Hemorsa Beach, CA. Stock AOS. PO owned it for 7 years prior and never changed AOS. Oil changes and a few other things, but that was it. I hit redline numerous times, everyday on that trip. I hit 140+ several times on I-10. 50,000 miles later, the AOS failed at 146k. I drove the car for maybe ~500 miles with a weird vacuum leak, but that was it. There is no performance decrease in the initial stages of a failing AOS, and masks itself as a normal vacuum leak (my RPMs would dip and hover around 1,000+). Oil on ground came next - bellows tube tear had gotten bad enough to leak oil, or it was teared long enough to finally drip oil. White smoke came next and I had it towed home because it wouldn't start (hydrolocked). When replacing AOS I found a lot of oil in the intake manifolds. Shortly after, bank 1 suffered a cracked head, which I believe was influenced by the prior hydrolock and only developed over time, but honestly I am not sure on that. There are other things I have speculation on that contributed to it. And no I don't buy into the "these heads just crack" thing. Car is now getting a used head and will be back on the road next month. Has been out of commission since July when I found the intermix. edit- before I get flamed again please take first part of 2nd paragraph with a grain of salt or apply some degree of common sense. There are other things that will contribute to a catastrophic failure.

Quotes source post: 19724974

This is not accurate at all. The factory AOS does not have to fail for the smoke to occur. In fact, the AOS can be in fine shape without any broken parts and you can see puffs of smoke when (1) you over fill the oil, (2) park on a hill, (3) during spirited driving. The reason is that the factory AOS cannot process the oil. This is why the factory came out with the TSB back in the mid 2000s to tell everyone to run half a quart less oil. Which is why many of us decided to go to the Porsche Motorsports AOS which could process "full" oil levels. But the PMS AOS CANNOT process more than full oil levels. However, the UAOS is designed to be able to process 1-2 quarts of oil over full depending on the condition of your engine as measured by a blow by test. Plus it can process the extra 2qts of oil sitting in your deep sump. I am currently running 12qts of oil in my 3.6 not counting what didn't drain out from the oil change. Think about that for a second. 2 quarts is from the 2qt deep sump, 1.5 quarts is from the UAOS and 8.5 is from normal factory engine level. I think it's great that you developed a very quick process to replace the oem AOS. But it's a poorly designed part that is suboptimal any way you want to slice and dice it. Quite frankly, it doesnt matter if you figure out how to replace it in 5 minutes and Porsche gives it away for free. Why would you want it on your M96 if it can't even process "full" levels of engine oil on a flat road in the midwest, let alone park it on a hill or decide to take a twisty or two. It's gonna smoke like a chimney WITHOUT EVEN FAILING. But I would argue in this situation, the AOS isn't failing, but it sure has failed to properly process oil.

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Have you had a water pump failure,,, or replaced the water pump..?

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come on man…look at this and think about it. dont overfill your car with oil. I thought that was common sense but I guess not. Of course what you described will happen. I am not talking about white puffs gc. I’m talking - like - if you hooked up a smoke machine to the back of your car. That’s what it’s like, and it comes from oil being burned in the combustion chambers. allcool - Good guess and good ask because I thought about this. I did replace my water pump - with a new gasket - and when I removed it, I thought I nicked one of the blades on the motor support bracket (because I didn’t remove it - you can I loosen the bolts enough to pull the support back and slide the pump out, eliminating several steps and saving time). I later read about the blade theory where it gets stuck in one of the passageways and thus gives you an improper temp reading on the car. I am hesitant to say this is what caused it, but I’m not ruling it out. Just seems far fetched. Coolant would still flow around the blade, albeit not as effectively. unless you had something else in mind? edit- and sorry yes want to clarify that when I removed w/p there was a blade missing.

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Check out Len Hoffmans site. He is the m96 head expert and has successfully/economically fixed cracked m96 heads by the dozens. He claims most all m96 996.1 cracked heads can be traced back to a water pump blade failure. The blade or small pieces of the blade lodge in 996.1 small very thin coolant passage ways. These too thin jacketed coolant walls, coolant passages, crack easy when subjected to lack of coolant flow, causing very hot spots that crack thru. Was your intermix oil in the coolant..? or coolant in the oil..? or both...? IIRR Len, or maybe it was someone else, claimed a 996.1 water pump failure after about 9 months always ends up with a cracked head. And most all these cracks happen in the same spots. When Len flushes the heads out, pieces of impeller blade always come flying out, so he says. If its not to late in your engine repair, check with him for a permanent head fix... Read his site and make up your own mind... In my mind, he is the MAN to have all m96 head work done. btw, lighten up on ole PT3, us old guys don't need all the BS. He is in the handful of guys that really help out around here. Hope I was of some help to ya... jmo

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1) it is interesting to note the crack happened near spark plug hole #3, near the w/p. I don't know enough about the actual structure/routing of the passageways, but the crack was next to spark plug hole 3. 2) It first started as oil in the coolant, then progressed to coolant in oil and dipstick milkshaked. Oil was clean at first, exp tank was milkshaked. Car only misfired once warm. That's when I knew it was a cracked head, though had hopes it was potentially the oil cooler. It was not. 3) I know... look @Porschetech3 I'm sorry man...Just feels like sometimes my input is quickly discarded and brushed aside, when I speak from firsthand experience and feel I have value to bring to the table that will save future owners the headache I am going through now. I will work on conveying myself in a way that is less offensive and more openly received. Want to make it clear that I am also trying to help out around here. And btw pt, I am the first person u want on ur side in a fight.....was sucker punched at Fado bar (center city philly) my senior year at drexel and was wired shut for 4 weeks. you always want someone on your side that really knows what it's like to get punched in the face.....my closest friends are the ones I've fought with (not always physically, but yes verbally).... 4) you were thanks brother.

@hkovalcik is your car a 2000 model?

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negative 01/98 - stock

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Please !

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Sorry about the off topic here guys, just thought a obviously distressed member with an engine failure needs a little help and insight... From Hoffmans blog. Note about half way thru the below quote I've highlighted in green the crack location Len finds on early 3.4 m96. "WHY DO 996 911 PORSCHE CYLINDER HEADS CRACK? October 20, 2016 gasketscraper Porsche 2 comments Click to see video of a 996 3.4 M96 head being pressure tested, revealing a microscopic crack that was not visible to the naked eye. This particular head was a prime example that a head can not be judged to be crack free without being pressure tested. We know where to look, but we couldn’t find this leak point until we subjected the head to 60PSI air pressure. Click here to read an article about our high-tech crack repair process. Anytime an engine overheats it’s no big surprise when it leads to a cracked head. But in many cases overheating was not reported. Indeed I often hear, “My engine did not overheat, so why did I end up with a cracked head?” I can not give a definitive answer, but I have some ideas. –I have flushed water pump impeller blade(s) from many -but not all- of the cracked heads I’ve repaired. Even if the pump has shed just one blade, if that blade makes its way to one of the very narrow internal head passages that feeds coolant to a specific area, that area will see a severe spike in surface temp. And if that area is one of those discussed in the Crack Repair article as having a thin cross section a crack is very likely, if not certain to appear. In this case the overall coolant temp would be within the normal operating range, but localized overheating will occur. A guage would be of no help in warning of this sort of overheating. If the head failure occured after the replacement of a water pump that shed one or more blades, I believe there is a high likelyhood that we can pin it on a blade lodging in a critical passage. It’s hard to justify pulling the heads after a water pump failure when the engine did not overheat. But these pieces floating through my engine would worry me. Seems like something of a crap-shoot. I would expect that the water pump was replaced because of some sort of overheating scenario. I believe it is pretty likely that the blades from these pumps don’t all break off at the same time; meaning at least one has probably been lodged somewhere in a head for some time. Even a brief, minor overheating event that was caught quickly by the driver can be harmful if one or more passages in a head is already clogged from pump blades. Crack propagation can occur over time and may begin with one major event, like a pump failure, blown coolant hose, etc, but take some period of time to spread from the water jacket to the surface. – On engines that did not suffer a pump failure or overheating event, but still managed to crack a head a potential explanation could be that the thin areas that typically crack are gathering points for casting stress. With the head mounted to a precision fixture on a mill, dial indicator mapping of the machined surface upon which the follower housing sits reveals that this surface warps, much like the deck of a head will. E very crack I’ve seen walked across this surface. On the M96 3.4 heads – which comprise over 90% of the cracked M96 heads I’ve seen- I routinely measure .002″-.005″ variance from twisting and sagging of the surfaces. These variances are evidence of stress. The act of cracking serves as a form of stress relief for any casting. These stresses are very much like earthquake fault lines. When the stress reaches threshold a crack will appear. Of course thermal shock increases the stress on these areas. The sort of stress caused by rapid warm-up of a cold engine could be enough to push the stress level past the threshold point. Heavily loading a cold engine greatly accelerates the rate of heating- and therefore expansion- of the cylinder heads. That significantly elevates the stress throughout the casting and could certainly lead to or hasten the formation of a crack. This condition would be magnified in winter months. And I have seen plenty of cracked heads in the winter months. "996 CYLINDER HEAD CRACK REPAIR October 20, 2016 Hoffman Home , Porsche 2 comments We have seen cylinderhead cracks in all models of M96 engines used in 986 Boxsters and 996 911’s up to and including model year 2001, but the 3.4 996 cylinderheads are far and away the worst offenders. Some of the cracks are very large and easily spotted, others are less obvious, and some are down right microscopic. Click here to see a video of one of these tiny cracks discovered during pressure testing. Visual inspection is not adequate for detecting leaking cylinder head cracks, as some are no larger than a pin head at the surface, as was the case with the head in the video. We had no idea where the leak was till we hit it with 60psi air pressure. Yet when we milled away the tiny leak point, we found a fair size crack beneath the surface. It is very common for small surface cracks to be atop a much larger crack, especially in the floor of the oil galley, where the leak in the video happened to be. Every crack has been in one of five areas beneath the follower housing.Never in a combustion chamber or deck area. Early 3.4 heads and some 3.2 heads had just two (instead of 3) coolant expansion plugs beneath the lifter housing. These heads have two locations that are subject to cracks. I have never seen a head that had more than one crack, but over time among the two & three plug heads I have observed 5 specific crack locations Each crack has it’s own unique fault line and a crack in any given position will follow pretty much the same path from head to head. Some radiate from one of the coolant expansion plugs over toward the nearest spark plug well. Others migrate from a valve guide bore across the machined spring well and end at the nearest spark plug well. Most cracks occur on the outer cylinder positions, but on occasion the center cylinder produce a crack that runs from a spark plug well across an exhaust spring well and end in a valve guide bore. Occasionally the plug well to spring well crack will continue from the spring well on to the nearest head bolt bore. These are the worst examples, but we can repair them too. Most of the cracks that gravitate toward a valve guide bore head toward an exhaust guide. However, the 3.4 heads that have just 2 coolant expansion plugs beneath the lifter housing will sometimes crack from a spark plug well to an intake guide bore. I have not yet seen this on a 3 expansion plug head. With over 25 years of cast aluminum crack repair to draw upon I have developed routine repairs for every type of crack that we see with these heads. The type that run into a guide bore are much more involved than the type that don’t and are therefore more expensive to repair. Crack repair requires a very specific series of processes to end up with a reliable repair. And the cracks that run through the valve guide area are the most demanding. Even shops that say they can repair cracks will often shy away from these challenging repairs, or worse do a poor “repair” that will get through the warranty period but fail down the road. Our repairs aren’t just a patch, they actually strengthen the casting. Every crack that we have seen with these heads has been to one of several specific areas I have identified as being skimpy in aluminum. When excavating the crack for welding we have a specific pattern that we cut in one of our mills to expose the entire weak area, not just the crack. As a result the finished repair has more material in the cracked area than it did previously. This is done using advanced welding techniques that involve the use of our custom built casting oven. Pre & post heating temp and cycle times are very precisely controlled. Duration of the welding process is closely monitored to ensure the casting is not overheated. We adhere to minimum weld cycle times divided by a specific period of time in the oven between weld cycles. This technique prevents the welding operation from introducing new stresses to the casting. When the weld work and intensive pneumatic peening of the weld is completed the casting stresses in that area will be long gone. What’s left is a much stronger casting. Next up, a pressure test. Once we have confirmed the integrity of the weld work it’s CNC machined with proprietary custom carbide tooling, then pressure tested again for added confidence in the finished repair. We have yet to have a single failure of a repaired head, and we know that some have been stressed hard on high-performance and even competition engines. It’s worth noting that as of 11-23-16 we have repaired 3 heads that went into service and later cracked in a different location. At least one of them was a dedicated track/race car. That’s 3 out of nearly 125 heads, so the odds are pretty favorable. In all three cases the new failure point was repaired and the heads put back in service. We have no practical way to predict these future failures and therefore can not guarantee that the repaired casting will not crack elsewhere at a later time. We can only guarantee our work, and that the head passed multiple pressure tests before leaving our shop. The large crack in the photos above is the most common crack we see with these heads. A lot of people think it’s a death sentence. And for good reason. I liken this repair to open heart surgery. It requires very specific skills, tools, knowledge and techique, in this case a major excavation of material and extensive welding and cold peening followed by a series of complex, precision machine-operations. The overwhelming majority of shops out there are not equipped to perform this surgery, but it’s routine for us. Our patients go on to live full throttle lives."

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No way?

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yeah man it�s brutal. Can�t tell if you�re being sarcastic haha, but yeah you�ll smoke out your entire neighborhood - I�m not even exaggerating.

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Hah. Just having some fun with you. Yeah I have had every type of AOS failure multiple times over the past 22 years on the track and street. Which I why I will never run the factory AOS ever again on the car. Nor can I recommend it. It's a problem waiting to happen.

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lol wait- just want to make it crystal clear there�s no �distress� because of my car and what I�m going thru with it. Has everything to do with the board and what ya�ll spread around here. I�ve made that clear. Still stand by everything I wrote, please don�t misunderstand that. I apologized to pt because it was the right thing to do, not because I agree with him. Don�t make me apologize and then tell people I�m crying because of my broken car like you�re doing here lol like wtf 😂😂😂 I can�t win- alright rant over. Said it before but I swear I�ll f*ck off now. Good luck with your cars all. Keep drinking the koolaid.

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if you are tracking your car, yes it is.

The Carrera M96/7 has a reputation as a "flawed design" ,and that has been deserved.....the AOS is a major part of that reputation with failures by now in the hundreds of thousands as evident in the 5000 full Threads just here in Rennlist on the subject and that is a small portion of the cars worldwide, most owners do not frequent Rennlist.. Th other design issues like IMS,RMS, cylinder issues have all been identified with solutions available... Everyone wants GT3/Mezger reliability..from the M96... The Factory AOS is a major cause of the bad reptutaion not only in in the vaccum leaks, smoking, Hydrolocking, cracking cylinders, but also in spun rod bearings , things that can/will cause catastrophic damage...and the resulting bad reputation... Even the second attempt of Porsche with the design of the Motorsport AOS doesn't help because it has the exact same diaphram from Mann+Hummel in the same location, but it also makes spun rod bearing worse by holding 1/2qt oil in the AOS body...it only helps to keep from smoking/ getting oil in the intake but at cost of oil in the Sump.... Your Apology is tentatively accepted at face value... I don't know yet what that is....at my age I don't get over things easily and with all the personal insults I don't think I should.......I don't know who you are and is like accepting an apology from a Ghost who just attacked/insulted you in every way possible.....and the accusations of "fear mongering" " spreading false information" are just unfounded... and totally **** me off ... If you want to be on my side, you will not be advocating for a flawed design, but rather help educating.on the benefits of a Superior Design... As far as your Procedure to install the AOS on a 996.1 in 2 hours, that is nothing new, Chris Murphy ( a regular Joe and not a professional) has been doing this for years on 996.1 cars in 2-3 hours and has installed the UAOS on all the 996 cars at a local track in the Northeast....If you had really kept up with this you would know that ....It has been mentioned here many times..( Note :: 996.2 cars and Tiptronic cars are much more time consuming ) I have no problem "agreeing to disagree" with anyone if we can drill down to the core......but I don't approve of long winded novels/diatribes that just expand the issues and conflate them...The only way to drill down to the core is to get to the point as quickly and concise as possible and leave all the unnecessary rhetoric out of it... My stance is the Factory style AOS System ( and even the Motorsport AOS System) is the major cause of the bad reputation of the M96 and consequential engine failures...and the UAOS System is the cure...The other design issues are less frequent but still important but there are cures for them also..