Engine failures

I keep reading a tremendous of unscientific nonsense when it comes to engine failures. That is the nature of the internet but somehow I am still surprised by it. The biggest piece of nonsense put out is a general lack of understanding of what system failures are. The laws of physics don't change from one car to another. If a part is going to fail under a given set of circumstances in one car, it will fail in every car where those circumstances exist. God may play dice at the quantum level but he doesn't play dice at the systems engineering level. If say the IMS bearing lasts 150,000 miles in one engine and blows up at 5,000 miles in another car, there is something different going on in the second car; either the part was defective or something was different in the way the car was used or maintained to make the part fail. Parts don't fail under identical conditions some percentage of the time. They fail in general use some percentage of the time because those are the instances where they are subjected to the conditions that make them fail. It is a subtle distinction but an important one. I constantly read anecdotes and crackpot theories put out by people who claim to know better regarding the IMS issue or cylinder scoring that make absolutely no sense because there are thousands of counter examples that disprove the theory. If infrequent use caused IMS to fail, they would fail in every car that had infrequent use, not just some of them. If driving and storing the car in cold weather caused the engine to score, it would happen to every car under those circumstances. If not, there is something else going on causing the scoring. Correlation not only doesn't necessarily equal causality, it can disprove causality if there are counter examples. With this in mind, consider three things, 1. There has never been a systematic explanation of why IMS bearings fail. No one has ever pointed to a cause or a set of circumstances where the bearing predictably fails for a known reason. All they have is conjecture and anecdotes of which there are many more anecdotes that go the other way. Since 90% of the parts never failed, any anecdote saying the part failed for this reason can be disproved by ten anecdotes that show the part didn't fail under identical circumstances. 2. IF there was a systematic explanation and flaw in the part Porsche would have found it. Every 996 and 986 Boxster that had a blown IMS in the first years was covered under warranty. The engines were all taken back to Porsche and examined. If there was a systematic failure, either with the manufacture, design or use of the part, any competent engineer with access to all of the failed parts and engine would have found it. 3. We know Porsche didn't find such a flaw because if they had, they would have recalled the part and would have fixed it. The conspiracy theories about Porsche knowing about the design flaw and hiding it are ridiculous. Replacing the bearing is a $800 job. Porsche was on the hook for replacing every blown engine under warranty at a cost of over $20,000 an engine. If the engineering studies had shown a flaw in an $800 part that was going to cause the company to have to replace 10% or more of the tens of thousands of engines being sold, they would have recalled the part. It would have made no economic sense to do otherwise. The only reason they didn't recall the part was because the engineers were telling them there wasn't anything wrong with it. And don't tell me the engineers were playing CYA over a design flaw they were guilty of. The engineers who designed the M96 engine are not the only engineers at Porsche and any competent engineer could have looked at the data and seen a defect if there really was one. Why did they change the design of the part? Because they thought the new design was better. That does not however mean the earlier one was defective. If it had been, they would have recalled it to avoid paying the resulting warranty claims. So what caused all of the IMS failures? There is one known way to kill an IMS every time, oil starvation. Oil is the one thing all of the cars that failed have in common and the one way we know the part will fail. On top of that, the two no kidding known engineering failures in the M96 engine relate to oil. The rear main seal was often defectively manufactured and was prone to failure causing oil leaks. The cylinder walls, if the block was not manufactured and pressed together under the exact right temperature, at the exact right pressure, would develop microscopic cracks that over time would expand into cylinder scoring which causes oil consumption. As a side note, don't believe anyone who tells you that the M96 engine has cylinder sleeves that fail, it doesn't have cylinder sleeves at all, or that it has Lokasil lined cylinder walls. Lokasil is a manufacturing process not a material. If anyone tells you otherwise, tell them to take some classes on metallurgy or welding and get back to you. Remember two other things about the oil system of the car. First, the car has one of the most unreadable dipsticks known to mankind and is notorious for having squirrelly electrical systems. This means most people if they checked their oil at all relied on the dashboard electronic measurement, which is hardly bulletproof and is only accurate if the car is on very flat ground even if it is working. Second, the oil drain plug has a metal washer and seal and requires a torque wrench to properly tighten. Don't use a torque wrench and over tighten that thing and it will bend the washer and create a leak. I have never seen or heard of a car that required a specific torque for the oil drain plug. How many people do you think ignored that and over tightened it creating a leak? A few I am sure. Put those defects together with the fact that Porsche sold the M96 engine in numbers unheard of by the company before then and you start to see what happened. Porsche used to sell only to enthusiasts. With the coming of the Boxster and the 996 it was for the first time selling in large numbers to non-enthusiasts. People who didn't know anything about cars. People who didn't check their oil. People who didn't change their oil at all or if they did did so based on mileage alone even if that meant leaving the same oil in the car for years on end. People who continued driving the car even though the warning lights were on. In addition no customer will ever admit that they did something wrong. Everyone whose engine ever fell apart will swear on a stack of bibles they checked the oil every day and never saw it coming. The reality of course is usually much different. Put it all together you can see what happened. People bought the cars, didn't check their oil or pay attention to the warning lights and were unlucky and had a small RMS leak or some cylinder scoring and were leaking and burning their oil away until finally they starved their engine of oil and the IMS failed. Others didn't change their oil and only drove the car once in a while and maybe had small leak they didn't notice and ended up driving on low oil that was too old to work well. Other people may have had a catastrophic RMS failure while driving, lost all of their oil, and been too dumb to immediately turn the engine off. Start adding those numbers up and you easily get to the number of failures. More importantly, you get failures that go across the wide range of mileage and use and conditions that occurred. After nearly obsessing about this issue for a year and reading every single book I could find on the 996 and every internet forum posting available on the subject, I have come to the conclusion, there isn't anything wrong with the IMS bearings in these cars. What is wrong with these cars is that they are prone to oil leaks and oil consumption and if you don't pay attention to that the engine fails.

Your remarks are consistent with explanations given in the book "996 The Essential Companion." However attempts to discuss these issues on this forum are almost always met with hostility and ridicule. On the positive side you are far from alone in your point of view. Happy New Year.

Two facts: 1- The original IMSB is a sealed unit that is permanently lubricated. If the unit is operating correctly and has not been exposed to Stage 1 bearing failure (failure of the seal) the engine can run completely out of oil and seize, but the IMSB will remain flawless. 2- The factory repaired hundreds of engines in the 99 and early 2000 model year, and used a metal matrix composite sleeve to do so. These were engines that had previously failed QC, but had to be repaired to fill orders for cars as the casting factory at Kolbenschmidt had burned, leaving the factory without crankcases. Read about this in the August 2008 issue of Excellence Magazine, in the Tech Forum that was written by the late Jim Pasha. This article was the first to uncover the backstory on lots of failures. The slipped sleeves became famous with these aforementioned engines that seldom made it out of warranty before the sleeve failed. Here's a classic photo that shows the "sleeve" thats supposedly non- existent clearly. M96 Slipped Sleeve caught in process. Here's a pictorial of photos from the same engine showing the various major failure points of the slipped sleeve before the engine became a total loss. https://www.facebook.com/media/set/?...4914693&type=3

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The IMS will die without oil. The lack of oil effects the cam tensioners and that destroys the IMS. As far as the sleeves go, I can only go by the design of the car. Even if there were "hundreds" BFD. The engine was made by the hundreds of thousands. The other 360 thousand or so engines don't have sleeves. And you showing me a picture of a slipped sleeve doesn't prove it had that sleeve when it left the factory. Any engine rebuild shop can bore and sleeve a cylinder and do it badly. And the bottom line remains. no one has ever come up with an explanation for the IMS failures. That alone shows that something else is causing the failure. If it were the IMS, there would be a consistent reason why it was failing

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JohnCK2014, 2 more facts: 1. You have now personally contributed to the misinformation you rant about 2. You have now been schooled on the IMSB and the factory cylinder sleeves

Who is more credible? A person "maybe an engineer" that has read every book and internet statement for over a year and come to the conclusion that low oil levels is the culprit. Someone that has spent years dealing with the failures and researching and fixing them with his own hands instead of internet or book theories. He posts pictures as proof of sleeves that don't exist and explains things he deals with for years on a daily basis. It is amazing to me to read the statement "there isn't anything wrong with the IMS bearings in these cars. What is wrong with these cars is that they are prone to oil leaks and oil consumption and if you don't pay attention to that the engine fails." If as John Ireland claims that the book "996 The Essential Companion" says the same thing I would be even more amazed and I doubt it does.

Ummn, Whats a "cam tensioner"? Are you referring to chain tensioners? If so, they are oil pressure fed, but they take less than 6 PSI of oil pressure to fully tension the chains. Trust that if you are cruising down the highway and your oil pressure drops to a point that would make these tensioners no longer function, that you'd lose a rod or main bearing well before anything else. When the chain tensioners lose oil pressure, they lose tension, this can certainly create a failed timing chain, or broken chain rail, but either of those would stand a better chance of occurring rather than a failed IMSB. If what you state is correct, we'd see signs of these failures along with the IMSB failures, but thats not the case. If we do see collateral damage, it is created by the failed IMSB in most every case. There are some instances where I'll see a compound failure, but they usually occur with sub systems that do not operate in unison. Further, a chain tensioner can completely fail and the engine still will not have a camshaft deviation thats enough to throw a CEL, which takes +/-14*. Please do your homework on this. You are completely off base. The engine that is pictured was a virgin engine, from a virgin one owner vehicle that was only driven 12,000 miles in 13 years. It had never been rebuilt, and had never been extracted from the car. Had that vehicle been driven more, the sleeve would have failed under warranty, like most all the others did. All you have to do is read the Tech Forum article, it was written by a long time M96 researcher and historian. Cylinder failure due to a slipped sleeve is MOF#1, it was the failure that led Bruce Anderson to tell Charles and I that we needed to start developing these engines, as he was receiving dozens of letters per month about cylinder failures. Today we hardly ever see this, in fact the one that I posted in that set of photos is the last one that we've seen here. They are just smart enough not to post them. Your statements aren't making sense. Have you disassembled an M96 engine to follow the flow path of the oil system? Sorry, the factory "layout" is a joke, and isn't accurate. Ever built one from scratch? Just curious where your first hand experiences that you are sharing here have come from.

John, there is so much stupid in your post it passed beyond funny. Car manufactures much bigger than Porsche have been caught covering/ignoring issues much bigger than a little engine failure. Its a simple cost thing. If they analyzed the chance of failure that they would have to pay for was less than the cost of replacing all of the units, the car companies will go with replacing a few expensive engines every time. Same reason Toyota covered up their issues, Chevy, and plenty of other less recent examples. In cases like the 996, its not even a significant safety issue so they don't even have to worry about news reports about killer cars with nasty crash scenes. While you are correct that there are high milage cars that have suffered IMSB failures, they are the rarity and do not disprove the accepted belief that low milage cars are more likely to fail. No one has claimed that 100% of low milage cars will fail or that high milage cars won't fail. Just that the former are more likely to fail. The 996 is far from the only Porsche to suffer cylinder scoring either, but a common thread is that the majority of failures were found in cold climate cars. Again, not every cold climate car has the problem, but the numbers are significant enough to suggest there is a connection. And calling the man that knows the most about the M96 outside of Porsche a liar (e.g. No proof the insert was factory) when he provides information about exactly where you can get more detail, pure class there mate. I guess you are yet another internet moron that bought the car but didn't research it before hand and/or can't afford the associated risk. That is assuming you even own one... Take the advise of those that have been there and those that actually know what their talking about. Learn how to take care of the car and get out and drive the hell out of it. You may have 500k miles or 5 before it dies because of the IMSB or (more likely) some idiot drunk t-bones you. Get out and enjoy every damn mile or sell it and don't look back. Those really are your only two options that will amount to anything worthwhile.

Damn, that one hurt so bad that I felt it over here.

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That statement makes us all full of loathing and derisiveness. Crappy New Year, indeed.

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If there was a common theme why would someone not post this? Unless it's keeping people in business I'm not smart enough to figure this out I'm sorry. Sitting on the fence about buying a 2000 6spd coupe with 87kms, the ims issue is the only thing putting me off. Don't care about the money if it pops, I care about getting stranded on side of the road with a pissed off wife waiting for a tow truck.

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Any 15 year old car has the potential to leave you stranded on the side of the road. Many with far worse odds that a 996 and regardless of how good of a PPI you get. The best you can do if you pick one up is do any of the maintenance you don't have hard evidence was done, do the other preventative/proactive things that you may be concerned about, and then enjoy the car . Worrying about how an old car may leave you stuck on the side of the road is just silly. If you can't handle that possibility then go get a new/CPO car that comes with road side assistance (because they can leave you stuck too).

I don't want to start an IMS thread to ask but since this thread has touched on it I'll try here..... The thing touched on that I'm curious about is "higher mileage engines fail at a lower rate'. My 2003 C4S is one of the IMSB types with the higher percentage of failure (@8%) However, it is at 89,000 miles and well maintained by previous owner. Frequent oil changes at 6000 miles and oil analysis every change shows consistantly promising levels Is there enough data on the rate of failure of high mileage vs low mileage of my bearing type to where you guys would expect the potential for IMSB failure in my high mileage engine is below the 8%?

Jake, the photo catching the sleeve issue in progress is amazing. Don't worry about the OP. I doubt he changes an air filter much less assembles engines. With your mileage, why not just change the IMSB with your clutch change (assuming your on the original clutch)?

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No. Your car fits the profile of being less likely to fail, but that doesn't mean it won't. There is simply no magic "this car is safe and that one is not" algorithm out there so all we can go by is what has been observed and reported about actual failures. All that evidence points to cars that are rarely driven (specifically getting up to temp for awhile and using the full RPM band) appear to have a higher rate of failure. It's also not just about changing the oil, but also about how it was driven for those 6k too. That you apparently have an entire history of oil analysis looking good is also helpful. If it were me and my car, I wouldn't panic over it and address it when you do the clutch or something else major. Ours is at 70k (miles), about to turn 15, and still rocking the original IMSB. It's a one owner car though and I'm willing to shoulder the risk of having to replace the engine over just waiting for the clutch to finally be ready for replacement. Only you can just your own comfort level of risk and if going ahead and getting the bearing replaced will help you sleep better, do it.

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lol, yeah ok.

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Clutch was done approximately 30,000 miles back. RMS and IMSB were not touched and are original as far as previous owners records show. I'm trying to determine my risk in waiting to do the upgrade. Making that determination isn't easy. I'm not expecting any one to say my engine is out of the danger zone but just want to know if I should believe I am likely below the '8% group' based on my mileage and history or is thinking that just whistling past the graveyard?

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ok. your risk level is 6%. Now, how is that going to change your life or the way you drive your car?

Interesting thread. For those of you who are considering buying, do your research, determine what risks you can take, then if you decide to buy, take care of the things that are on your mind without delay so you can sleep at night. AND STOP WHINING! Jeeeez!!!!

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Excuse me, ma'am - your slip is showing.

I do love the belligerent posts that smack of ignorance, wrapped up in a veneer of half-assed Internet research. Although it does get tiresome, it is always fascinating to watch the progression: Someone shows up, posts up THE SAME CRAP that's been posted ad infinitum in the past without adding any new/valuable content, and then gets butthurt due to the resulting backlash. While you won't find me on the carpet in front of Jake's recliner (*cough*KK*cough*), calling the man out as a liar is both ballsy and stupid. Since this is one of the few recent flameout threads that I'm not responsible for, I'ma sit back and watch the destruction. Burn, baby, burn!

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agree with everything you posted except for ONE... should be AD NAUSEAM

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If I trusted your assessment it would make me 'feel' 25% better than I did before. Seriously though....it wont change the way I drive but if there was some margin of security to be calculated by the mileage/condition of my particular 996 specimen compared to the other high risk specimens it could make the period between now and the inevitable upgrade a little less worrisome. Less worry is good. If my simply seeking a clearer assessment of my own personal risk exposure makes others uncomfortable I'm not sure I should care about that since my looking for clarity isn't infringing on others in any way that I can think of. Others are free to dismiss my concerns as silly if they choose to. I'm a big boy and it's only the internet. I'll get over it....it wont take long...there...over it...didn't take long at all now did it?

As a doc I feel for Mr. Raby. Similar to his experience, I would have patients coming in and self-diagnosing their ailment based on internet "research". If my professional opinion based on years of training and expertise does not align with their wisdom I am called a greedy profiteer, liar, callous and stupid. If I show them the MRI's, CT's or what not (similar to the picture posted by Mr. Raby of the slipping sleeves) I am told that there must be an error, the imaging tech was drunk, and again, I am an idiot. And similar to Mr. Raby after receiving that much hostility in exchange to your best efforts and empathy you stop giving a **** and say whatever. Sure we do a disk herniation surgery as you diagnosed instead of a GBM as I diagnosed based on the images. Sure, it does not apply to you. Sure, the internet provides you with all the information you need to equalize my 25 years of experience, 12 years of training and countless hands on procedures. Thank you to mr raby and countless other contributors that make us aware of the problems in our cars and provide people like me with ideas and solutions.

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I don't think anyone has put together a table or chart that analyzes percentage of failures vs mileage that a car has achieved. I don't think there is a repository of information of the failures complete enough to put something like this together. Thus we/you are left with the anecdotal evidence, or commonly accepted belief (whichever you want to call it) that bearings in cars with higher mileage fail at some undefinable lesser rate.

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I just changed my clutch, IMSB, RMS and AOS... I'm STILL afraid of failure. Man, I picked a bad day to stop sniffing glue! TC

I just read the OP's first post due to it's length, I originally skipped it. He obviously does not know what a single (or double) row, deep groove, ball bearing looks like, the types of seals it can have, and how it is lubricated from the factory (grease). That original post was a lot of words that can be disqualified due the conclusions. And I try not to post to these threads!

[QUOTE If as John Ireland claims that the book "996 The Essential Companion" says the same thing I would be even more amazed and I doubt it does.[/QUOTE] Page 182...or you can start at page 179. Also see warning box on page 174 re: VariocamPlus and engine oil levels and pressure. For me this is like the chicken and the egg...or which end of the shaft broke first. We know that things have broken...it is just that some of us are not satisfied with aftermarket explanations or solutions. An other analogy is removing one's prostate at the first sign of elevated PSA levels. And some of us will search for more definitive information before acting.

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The problem is that while you at least didn't create a brand new thread as most do, you are still asking the same question that has been asked over and over with very little variation: "I [just bought | am looking at buying] a [1999-2004] 996 with X miles. Should I replace the IMSB?" Your post was refreshing in that you A) didn't start a whole new thread and B) had some interesting (if ultimately non-impacting) additional information about it's history. The end result is always the same too. "If you are worried about it, change it." Wether you do it now regardless of your clutch or you wait for the clutch is a personal decision. We can't tell you if your motor is going to crap itself. We can't even tell you that if you replace the IMSB that your motor won't still crap the bed due to other issues (Cuda is an unfortunate example of that ). All we can tell you is that the evidence suggests that you are somewhere between 0.000000000000001% and 100% less likely to have that particular failure based on the information you provided. You ultimately have to discuss it with people you trust and make the final decision based on your acceptance of risk (which is not just the potential cost, but also being able to live with the "am I doing the right thing") versus the cost. We can't make the decision for you.

Dammit, I'm gone to Spain for a week. When I finally get decent internet service, I check the "good week in the 996 forum" to see what's up, and see talk about epic stupidity again this week. So I start browsing and find "VOILA" another freakin' IMS thread, this time setting a true standard for idiocy. My real disgust, though, is that you guys let it get this far without even one decent photo: BOOBIE THREAD!!!

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You know, I just remarked to my wife the other day that I was shocked that there hadn't been an IMSB thread for a week and then one pops up. Now you say you've been away from the internet for a week... So it's your brigade of sock puppets that has been perpetuating the IMSBS all this time. Nicely done sir, too bad you slipped up there at the end and gave it away.

Just tryin' to make a little lemonade out of the abundance of raw material provided herein. Oops - almost forgot to add the sweetener:

Did I mention that I just purchased a new trickle charger?

Contrary to the OP's post, actual failure of the bearing itself has been traced to an almost exact cause, thanks to Jake and his crew. You only have to read about it for the theory to make perfect sense.

Sometimes, just sometimes, mechanics can go haywire. Normal goes to unusual with just a very little effort. Sometimes all it takes is a lack of lube...other times it just may take a cool breeze. Case in point...

I think the OP has left the building.

John Irelands quote "For me this is like the chicken and the egg...or which end of the shaft broke first. We know that things have broken...it is just that some of us are not satisfied with aftermarket explanations or solutions. An other analogy is removing one's prostate at the first sign of elevated PSA levels. And some of us will search for more definitive information before acting." If you aren't satisfied with either aftermarket EXPLANATIONS or SOLUTIONS what are you satisfied with? I think you have all the definitive information that there is and you've chosen not to act which is each owners decision. In your case you bought insurance, in some others they replaced parts, some never bought the car and some sold them, in others they did nothing except drive the car, in all of the cases there will still be some cars with no problems and some with. If you aren't comfortable then obviously you need to take a different action. I think the original post was stupid by someone who I don't think even has one of these cars who just wanted to stir up the pot.

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Hi...great to see everyone in such a cheerful mood. However what you refer to as "all the definitive information that there is" just isn't definitive enough for me. I think there is more to learn and whatever it is, it may be useful to know. In fact I've come to actually enjoy discussing the IMS bearing because it is a multifaceted mystery...sort of like the Kennedy assassination single bullet theory. Some believe it and some don't. I think Mr. Coffee, Joe DiMaggio, killed JFK because of the President fooling around with Marilyn. In the meantime engines break or they don't break and we fix them or we don't have to fix them. And some of you will ignore these threads and some of you will jump up and down in pious fits and rants at the mere thought of them, and some of you will be curious enough to read them. The only thing, for me, that does taint this forum and leave a rather foul stench is the lack of civility that so many of you seem to express. However keep posting those pictures of your wives...I think I've already met several of them.

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Johnny Irish...there will come a day when you have been a member for more than 3 months and you too will get tired of these threads. There is nothing new to add concerning the IMS. I promise. I get that the fear of a major engine failure causes worry, angst and anxiety. I also understand that just talking (or reading about it) tends to lessen your anxiety. There are other ways to relieve all that tension. And yes, you are welcome to use the picture of my wife that I posted above.

John, I understand your inquisitiveness and desire to understand more about the IMS, and I also understand that some forum members get quite sick and tired of reading about any facet of the issue. Some of the ire is probably due to the frequent reminder of the single biggest and most frustration failure point of these cars. People don't like to be constantly reminded of something that is negative and is not fully understood. They have dealt with the issue in their own way, and don't like the issue constantly hashed and rehashed. I personally think that those who lash out at people like you who begin the threads do so for a variety of reasons. For some, it's something to get worked up about. Something to do. Others have a need to berate people (pride, ego, and self esteem issues) and unfortunately forums seem to bring out such rudeness in people. I would suggest, as others have, that you search the forums for past threads that have discussed the same issues, same thoughts, same conclusions, same questions, etc, etc. You will find quite a lot to think about and learn that has been covered before. IMO, it would be better to add on to those threads if you have a new or original thought. And finally, for those who don't want to read about IMS issues anymore, just move on. No need to be uncivil. It doesn't make you look better, smarter, or superior in any way whatsoever to insult someone or their thread.

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Or...these posters could (and should) use the sticky. That's what its there for.

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I applaud your wish for more knowledge and agree that there could be more to the story that could help us better understand the issue. Until you actually have some real facts and something to back up your technical experience, however, you continue to just be another new 996 owner dredging up an overly hyped and discussed issue for no other purpose than to hear yourself talk and **** off the people that have already lived through years of people just like you. For an encore are you going to start threads about the best oil to use and how Porsche is in league with Mobile1 to destroy our engines? So please go out and enjoy your car and share the joy and knowledge available in the plethora of other threads and subjects about the car.

Wow. How long have threads like this been going on. Didn't these cars start blowing up in 2000... Good entertainment. Buy an air cooled car drive it and sell it for more when your done. End of IMS story....

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no,...it isn't

After much introspective contemplation, my thirst for knowledge and quest for definitive answers on this fabulously interesting topic have led me to the following conclusion: I think we like these threads better once they've been boobified. The viewed count always spikes up. Gonzo, this one's for you in response to the incredible turquoise cowgirl.

^^^^ I think her cylinder liners have slipped

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Yeah, Baby!

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Hello Gonzo911 and Spokayman and thanks for the thoughtful replies. My biggest fear, as someone else posted here somewhere, isn't the cost of a rebuild...I just hate to breakdown in the middle of nowhere in the middle of the night. I hate sitting and waiting for a flatbed and listening to my wife cry. I hate having to pee in the dark in the middle of the Mojave on the one night a year all the Tarantulas come out to mate. I hate mechanical failure. When I smoked and drove Alfas I even carried a spare cigarette lighter. Whether it is Jake or AutoFarm or someone else, the IMS issue is still unsolved...for me. And reading "old threads" isn't going to turn up new material. Years ago they used to put polio patients in iron lungs and body casts and braces. Then they came up with a vaccine. And so in the spirit of asking questions I will continue to explore the issue. Warmest regards and happy New Year.

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John....there isn't anything new. That's the point. I do wish you a Happy and Healthy New Year too!

The Fembots are new...(to this thread at least)...

I am not scared of getting stranded. I carry a gun, a lighter, vodka and smoked jerky in the car. If I get stranded, ****ing A! Adventure!

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See now that makes sense to someone like me with a background in metallurgy. While IMSB failure presents as a singular event, it is in fact the culmination of a series of events. I suspect there may be a tiny, tiny percentage of bearings that fail from manufacturing defects or poor assembly, but the vast majority fail via a set chain of events. The mileage at which failures occur is proportional to how long it takes for each stage to be completed, and that is affected by other variables such as oil-change frequency, heat, and rpms, etc. And the reason the double-row and large single-row bearings have a lower failure rate is that after the other events have taken their toll, the higher load-rating allows the wounded bearing to hold together longer...perhaps until another failure mode takes the engine out. Analagous to the way a two-by-four with a 1/2" crack will hold together longer than a one-by-two with the same 1/2" crack.

Ben, it may take the dual row or the larger one longer to fail after the stage when they start but if they are shedding metal it is going thru the other bearings and damaging them even though the IMS bearing itself is holding together. The stock oil filter housing bypasses some of that metal allowing that to happen. If the stock filter housing is replaced by the spin on filter housing it supposedly doesn't bypass anything so the metal particles are trapped at least saving the other bearings from damage until the IMS bearing finally fails or gets replaced. I think the new bearing is not sealed on one side and relies on engine oil splashed on it for lubrication. This is the way I understand it but maybe I'm wrong. IIn any case there are some IMS bearings that do not fail at all, why some and not all is the question that does not seem to ever get a definite answer.

Anyone remember the Twilight Zone episode where Shatner keeps seeing the gremlin on the airplane wing, tearing into the engine? Each of these threads is like looking out that window...

Well, except that sometimes boobie pics show up.

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Simple. Put this in your glove box: Oh, and before I forget: .

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Cuda...thanks for getting this thread back on topic. Your pic is proof positive that an aftermarket retrofit can be a major improvement over OEM.

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+1 I love this place. It's the 'Disneyland' of boobies.

Even after a self imposed ban I see ground hog day is alive and well....day after day after day. Someone say boobies?

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oh bull****. All these sob stories about wives and crying and middle of nowhere. how often are you driving in the middle of no where? Even more so, how often is your wife driving your car, alone, in the middle of no where? Why is your wife crying if you are there? Is she that delicate? Your true concern is paying $12-$15k for a new motor with a car worth barely more than that. Lets be honest here.

Quadcammer, this appears to be one of those semi-rare occasions where we see things the same way. If one's primary concern is never breaking down, 10-15 year old sports cars don't seem like the logical choice. A Prius sounds ideal.

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LOL, is this what I think it means?

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Says the man that used to drive a 88k Ferrari 308 GTS...

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That my friend is Trollism (SIC) at it's finest. As is so often the case with trolls, they focus on a micro-facet of the issue at hand and try to force their lack of understanding down everyone's throat, whilst maintaining an air of inscrutability to hide their ignorance. Don't even bother, it is the same as arguing with a religious zealot, first they pretend to have reason and rationality, as that is eroded they sink to personal attacks on the credibility of the people who really know their stuff, then they simply apply dogma. All 3 stages have already been passed

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The worst situations involved running Monte Carlo style rallies through the California/Nevada deserts at night...hoping the range cattle didn't decide to cross the road as we were passing a Citroen SM at 110 mph...at 2 in the morning. She actually didn't cry but she did say she felt close to death. Another time I was driving my race car home from the Palm Springs vintage races...my wife followed in the family sedan. The race car broke and we came to a stop in a small triangle where two freeways merged. This time is was a little after 11 pm. She held the flashlight while I worked on the car and the traffic raced past both sides of us about four feet away. We got the race car going and found shelter at an all night Mobil station in Colton. We got home at four that morning. I have always appreciated how supportive she has been of my motoring adventures. If my literary depiction of her in my previous post was lost to you...well so be it. While I certainly wouldn't like to pay 12 to 15 thousand for a new motor for any car...I also think my 996 would be worth it regardless of the current Craigslist values. That's why I bought it in the first place. And once again I have replied to an obviously hostile post without stooping to the level of the person I am replying to. And once again a thread has been hijacked by people who would chose to suppress discussion rather then just ignore something that doesn't interest them and move on.

OMFG, these threads are so annoying. Here you go: Find car that has been "driven" not a garage queen, do a PPI "before" you buy it, change the oil "OFTEN" after you buy it, send to lab for analysis, if you are really nervous about IMS change out the IMS and most importantly drive the car and enjoy it!

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You keep saying that, yet you and the endless stream of new owners before you have yet to bring up one signal useful fact that changes what we already know of the failure and how to avoid it. You just continue to speculate on past speculation and ignore what has been shown to be true. If you want a discussion, then bring provable evidence that contradicts the current information. Until then it's not a discussion, it's just idiots that don't read and/or refuse to accept what they read causing trouble and keeping an issue alive that should be long dead. If you want to be taken seriously, you need to get out there and do the hard work to earn a reputation that you actually know what you are talking about. Until then you continue to just be an annoying troll. We don't walk away from the idiocy of threads like these because if we did those that didn't know better would stumble on them, see no one questioning the stupidity, and therefore believe that it was true (and likely start spreading the same idiocy themselves). By responding to the threads we show you for the trolls and idiots that you are.

I totally agree. What kind of complete dumbass does not care about a blown $15,000 engine for a $20,000 car? Sometimes the idiocy posted here by people that don't even know the IMSB from the IRS just baffles me.

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I hate having to repeat myself... John....there isn't anything new. That's the point. The biggest problem with threads like yours is that further amplifying this overblown, rare and (I am sure) many times misdiagnosed failure event causes 3 things: 1) People researching the 996/997.1 to decide not to buy one 2) People selling their well maintained and well running 996/997.1 to get far less than they are worth. 3) Irritation at having to read the same **** over and over and over and over... Then again, I am sure you like the attention.

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Indeed. .

Cmon guys. Can't we have a discussion?

About MILFs?

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Is that a MILF, I thought it was a DILF, I suppose everything is dependent on perspective! Does anyone know why the IMSB fails? I've heard that lubrication is important, but ribbed and dotty is OK!

I want to thank OP for reminding me of all the people on the internet who post clueless information while purporting to be experts on the subject. And I want to thank everyone else for some great responses and the best informational photos this subject has seen in years.

Discussing "MILF's" is certainly better than discussing and comparing IMSB's or lay shafts.

The bottom line of this entire thread is all of you people admit you have no idea why the part is failing. Yet, you have this faith based belief that it is the part that is failing because the part is defective and not because of something else, like oil, causing it to fail. That is unscientific nonsense. It doesn't matter whether you are a mechanic or not. The data is what it is. And when a part is failing in completely divergent and inconsistent circumstances, it is not that part that is defective. Something else is going on that is causing the part to fail. There seems to be an entire industry based on the denial of that simple fact.

John: You need to study the single row, deep groove, double sealed ball bearing configuration and lubrication method.

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actually it is based on observation, which is of course highly empirical, but I suspect you won't understand what I just said.

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We have a logical theory based on the study and efforts of the most accomplished M96 mechanic/engineer outside of PAG. In the end it actually doesn't matter why it fails. What matters is that we know it fails, the usage patterns that suggest failure is more likely, and how to mitigate the problem (treat it as a service item). Showing clearly that you haven't researched the issue at all and just want to spout nonsense. The most common correlation in the documented failures is low milage cars. In those situations it is believed that the engines are not being warmed up long enough and regularly enough to burn off contaminants in the oil which lets it become acidic. This is further compounded by OCIs too long for such a situation which allows the oil to damage the seal. Its not the oil itself and its not the bearing. Its the combination of the two in an environment that allows them to interact poorly with one another. The bearing isn't defective so much as a non-ideal solution to the situation. Just what evidence do you have of these divergent situations? Do you somehow have a absolutely true and unbiased history of all the failed engines that no one else in the world has? The reality is that customers lie intentionally or not so there is no way to compare two real world examples scientifically and come up with anything more than a working theory. Theories aren't facts, they are just best guesses on the information available at the time. Maybe Jake's wrong (and he doesn't hit me as a guy that can't admit when he is), but in 10 years no one has offered any better theories with any data to back them up.

The obsession with the IMSB misleads potential 996 & Boxster buyers into thinking that this fabled bearing is the primary Mode of Failure.The risk is that if the bearing has been replaced recently ,the misinformed buyer thinks all is well. Actually it is not 'well' unless an M96 specialist says so ! Finding that specialist seems a much neglected subject compared to all the IMSB hand-wringing.

"he most common correlation in the documented failures is low milage cars." Correlation is not causation. More importantly, there isn't any correlation. For every low mileage car that suffered a failure, there are many others that didn't. Correlation means "if this then that". It doesn't mean "sometimes this". We are talking about mechanics and phyics here not social studies. If not warming the car up or not using the car very often caused the part to fail, it would cause it to fail every or nearly every time the part was subjected to that, not just some of the time. And as far as the "empirical study" the only people who ever did any actual empirical study and had access to a statistically significant sample of failed engines was Porsche, who had access to every engine that failed under warranty. And they never found anything wrong with the part. It is all bull**** people. Complete and total unscientific bull****. You guys sit around and listen to people who have an economic interrest in convincing you the part is the problem and you believe their have half assed anecdotal evidence and half baked conjecture. That is really all there is to it.

"Just what evidence do you have of these divergent situations? Do you somehow have a absolutely true and unbiased history of all the failed engines that no one else in the world has?" The evidence is the endless number of anecdotes of all of the failures. You can find failures in low mileage cars, high mileage cars, cars that were tracked, cars that were not, cars that were alledgedly well maintained, you name it. There is no consistent pattern. If there was, everyone would know what the problem is. They don't know what the "problem is" because the part is not the problem. The problem was different in the various cases.

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In my experience people who pull "correlation is not causation" out of their backside, do so for several reasons: 1- They don't get what that phrase means (about 50% of the time) 2- They don't understand how to apply the concept (about 20% of the time) 3- They use this phrase to obfuscate that they have not done the research or analyzed the fact sufficiently to form an empirical opinion, and are way to lazy to do the work required beyond trolling on some forum, after all, getting educated is complex, trolling is easy (about 20% of the time), and, perhaps because they do not have the necessary education background to allow for deductive reasoning and fact analysis. Which leaves a mystery 10% (no doubt the experts!), which I assume you believe you fall under. So here is my question to you, as Porsche chose to settle in the class action, they obviously had some thoughts on the matter, as around 8-10% of engines were covered by this class action (note: 8-10% of engines, NOT 8-10% of engine failures). What is the actual cause of engine failures, specifically the IMSB failure that was subject to the 8-10% of engines that Porsche agreed were IMSB failures? Or was Porsche simple taking the path of least resistance, by throwing some money at the problem and really didn't care/weren't aware of what the problem was? Further, I spose I should meet your opening line head on, here is where the problem is with your reasoning: You assume that because not all IMSB's failed at the same time in the same manner, that no one knows what they are talking about. This may be true, but in your ignorance, you are completely failing to address any number of variables, including but not limited to, manufacturer of bearing, batch of bearing, driving style, temperatures, installer, variations in seals, variations in grease, and any number of other parameters. Correlation may not equal causation, but if you have a repeat failure of a single component, and that component doesn't fail when it is replaced by a component of higher quality, thousand of times over, there is enough correlation to infer that the failed component is indeed to blame. The blame may be due to a number of reasons, including insufficient component specification, bad installation, or any other piece of bull**** you wish to pull out of your ***. And I haven't even mentioned the Mezger engines, which also have IMS's, but a different bearing lubrication setup, and never suffer from this failure. Fact is, the IMSB's failed repeatedly, Porsche owned up to this in court as it being an engineering/manufacturing fault, when the IMSB is replaced with a superior build quality model it does not fail again (less than .1% of replacements, from what I can gather). BTW, please can you tell us what your greasemonkey/engineering background/experience is?

...and that my friends is the mentality of a true vendor hater.

JFC it takes a real moron to dispute the data that Jake shares.

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So not only do you not know what you are talking about mechanically, you don't know how to properly use the english language either. Correlation is an observed pattern of similar data points across a majority of the studied events that may contribute to the results. Causation is an observed pattern of similar data points that directly contributes to the results. In the real world failures there is no way to know all of the facts of any given motor (OCI used, oil type, driving patterns, etc..). As such all you can have is correlating evidence to base theories on. There are always going to be outliers in any study. They don't directly negate the associated theory though. For all your banging on about being scientific you really don't understand the principles of scientific study. Get it through your thick skull, no one has ever said there is a specific known cause. There is simply a yet to be disproven theory that says that low milage cars have a higher chance of failing. Not that every low milage car fails and no high milage car fails, just that the low milage cars appear to fail more frequently.

Johnck2014, Do you change your own oil?

Yeah, sometimes olive sometimes vegetable, depends on what he is cooking.

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to paraphrase you "that hurt so much I felt it from over here"

Showed up for new boogie pics and nothin!

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If vegetable oil comes from vegetables, and olive oil comes from olives...where does baby oil come from? Should we start a new oil thread?

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How about this? All the people who don't want to read another IMS post just jump over them and ignore them. All the people who are interested can read them and reply. Nobody has to make nasty and unnecessary comments about other people or their motives...I respect you and you respect me and you read and make the posts that interest you and I'll do the same. Referring to people as trolls or calling them idiots or stupid because they see things differently than you is truly uncalled for.

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If you read my posts then you will be able to respond intelligently...perhaps.

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Or how about people that want to discuss the IMSB actually use the thread that is dedicated specifically to the subject and always remains visible ahead of all other (non-sticky) threads? Basic accepted edict in any forum is that you read and use the sticky threads when discussing the given subject. I don't care if you respect me or not because I certainly don't respect you. You have not done anything yet to earn respect and in fact have done quiet a bit to not deserve it. I'll call any troll that I come across a troll because that's what they are. The same with stupidity. No new evidence has been presented so there is no discussion here. Questioning what is known without any information or cogent theory to backup the question is stupid and the people like yourself and John that want to stick to such a flawed line of "reasoning" is the definition of idiocy. As I've continued to say, if you, John, or anyone else actually has new information to support alternative theories/solutions, then by all means please present it and we can actually have a discussion about it. Just saying "I don't like it" and ignoring the actual definition of terms like "scientific method", "research", "correlation", "causation", and "all" does not promote discussion. It promotes derision, and deservedly so. It occurred to me this morning that none of you people that start these BS threads have any intention of replacing an engine if it fails. Your real concern is that your "investment" may suddenly drop 3/4s of it's value in an instant, but rather than accept the wisdom of those that have been through all of this and replace the bearing regularly you'd rather **** and moan and not do it (thus putting you at a higher risk of what you fear). And let's be honest here, at a 60-80k interval (clutch life) the likelihood of you having to do it more than once is smaller than your chances of the bearing actually failing. I'm sorry for all those that see the inflated values of other 911s, think they are getting a steal with the 996, and then figure out the stark reality that they are not an investment, but that is what it is. They are good strong and fun cars that are under appreciated due to being slagged on for being the first water cooled 911, having "funny" headlights, and being "mass" produced. Then all you people spun up this hysteria over the IMSB and further sealed its fate as a "budget" 911, but just because you can buy one cheap doesn't mean you don't still have to pay to maintain it.

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Jake, he hates everybody here... Not just vendors. No special status for you.

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If Porsche never found anything wrong with the part, why did they upgrade the bearing on the late 2005 models?

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There is a shop with tons of experience regarding failed M96 engines. More experience than the manufacturers own dealer network... I have NEVER seen the guy you are accusing, try to sell anybody anything. He offers solutions, solutions that appear to work better than anybody elses. He is VERY upfront about the costs. He has LOTS of experience tearing into and fixing these engines. Trying to impune his character like that just proves to me that you must have a reading/comprehension issue, and you probably just like to stir the pot.

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Blah blah blah....you go on and on...but I won't bother to repeat your bad manners by attacking you or others with imagined motives. As a mechanical discussion regarding the general wisdom pervasive here at Rennlist I offer not my own opinion but that of an outside voice. I do not offer it as some magical final word on the matter but rather a reason for more discussion...and perhaps comments by the professional mechanics who post here. Mr. Adrian Streather has written many books on the 911s. "996 The Essential Companion" (with forward by Jurgen Barth) published in 2008, the same on the 993 published in 2006, another on the SC published in 2005, as well as Buyers Guides covering almost all the models. As it relates to the 996s I will simply refer you and others to Chapter 3 - 996 engines...and specifically pages 179 through 185 plus the warning box on page 174 regarding Variocam and VariocamPlus systems. Let's only hope that this does not get turned into attacks on Jake or Streather. One sells books, the other sells mechanical services. There is nothing wrong with either and both provide useful services.

Yeah, cmon guys. Just have the discussion that has been had literally over 100 times on just this forum alone so many times that there is a sticky on the topic. JUST HAVE A DISCUSSION!!

John, the guy wrote a book and devoted 6 pages or so to the subject. Jake Raby has devoted a good portion of his life to the subject and posted plenty of info on here for free. Many forum members have thrown their two cents in as well. There is an IMS sticky that takes hours to read. Everyone that reads this stuff has more than enough information to make a decision. You made yours, I made mine, if something NEW comes along than start a new thread, nothing new, no new thread.