Let's ignore the issue for the moment and concentrate on the Jalopnik "survey". The author may have had good intentions but IMO the methodology is fundamentally flawed--and in several ways.

1. For the number of cars at risk, the number of respondents (if I remember my college statistics class) only results in a margin of error of 10% or worse.

2. Any survey that relies on the respondents to self-report is flawed. A survey that only pulls data from self-responders from two web forums is even more flawed.

3. The survey did not accept respondents whose cars had already grenaded but who hadn't joined Rennlist or Planet 9 prior to the survey or incident. I don't even know where to start with that one... .

4. The author's conclusion is that the issue is overblown AND that if a bearing hasn't failed by now, it is unlikely to fail.

This final conclusion is what gets me the most. The author only takes maintenance into account--which seems to NOT be a factor in the failures. If I'm buying a used 996 or 997, am I more or less likely to have my bearing fail if I buy a well maintained garage queen with 10k miles or a well maintained daily driver with 75k miles? What if I buy a high-mileage car and then drive it only sporadically? Have I increased my chances of grenading an engine?

No one can say for sure because the data is so spotty that no firm conclusions can be drawn.
I have no horse in the race. Frankly, I wouldn't buy a 996/997.1 for the simple reason that even a 1% failure rate with an item that destroys an engine in spite of my meticulous maintenance is a chance that I choose not to take.

I appreciate that people are trying to settle the issue and I really want to know the actual numbers, but to do so would require a more thorough polling of 911 owners--past and present. To date, no one has done that, AFAIK.

Agreed with all.....

True story... when these engines began to blow, I worriedly asked the shop foreman at my dealer about them... he said something like "with 25K miles on your car, it won't blow... will last forever... they all blow when new". It then blew at 47K miles. The next engine blew after 150K miles on that engine.

As you note, NO ONE knows except Porsche. Even the dealerships who see this carnage have no idea as they don't always know the reason for failure and may only see a small percentage of failed engines out of warranty as their work is so darn expensive. My first engine was simply crated up with an oil sample and shipped back to Germany. The dealer said "we are not allowed to take them apart". I suspect Porsche was still trying to figure out the mess. The second was way too dead so I sold it as a roller... the new owner pulled the IMS and it was fine but he stopped there so we don't know why.

I have listened to many experts... and I do mean that... experts.... and they differ. Even guys like Jake Raby don't fully understand the "why" of all failures.

In short, it is a flawed engine design constructed to save the company money when the company was failing. How do I know that? I am an "expert".

Peace
Bruce in Philly

This is true--lots of failures of motors on cars whose owners did all the prescribed maintenance (and often much more). The next question is did those motors show no symptoms of failure beforehand. The classic symptom is metal shavings in the oil. Did the owners of those vehicles disassemble the oil filters to look for shavings during oil changes? I suspect not--if you've got a luxury sports car from a German manufacturer known for high quality cars, you're probably not ripping apart the oil filter.

If you look at things like the IMS Guardian, they work off detecting metal shavings in the oil--which seem to indicate that the IMS doesn't fail instantly. Otherwise, the Guardian wouldn't be all that useful. A light that comes on after your motor self destructs to let you know the motor just blew up would be a little too late.

If the IMS bearing failure is gradual and not instantaneous, I can check my oil filter for signs of metal shavings. If they're not there, I can comfortably relax and not worry about the issue. That sentiment, however, relies on two assumptions : 1) There are no instantaneous failures and (2) the time of a gradual failure has to be longer than an oil change interval. Considering that Porsche originally specified the oil change interval at 20,000 miles, I could certainly understand a failure happening where no one noticed any metal shavings.

In my case, I change the oil twice a year (at about 3000 mile intervals). I *hope* that is frequent enough to notice issues, but I don't have any hard data to back that up. I check the filter for metal and send off a sample to Blackstone for a little bit more analysis to back up my visual inspection of the filter. That at least gives me some comfort that I'm being proactive about my IMS and that it's not a ticking time bomb waiting to go off.

Bruce, you could provide some of the statistics I'm looking for (well, at least 2 points of data are better than none). Did you notice an increase in metal shavings in our oil filters before the motors blew?

No warnings at all. I maintained the heck out of them... I am sure I was one of the more neurotic of their customers.

The first failure occurred gradually over a few miles. I had a gradual loss of power accompanied by what sounded like marbles in a hard plastic box. This got louder and louder. I was driving home to my sister's home in Atlanta. I remembered the "advice" of the Porsche shop foreman something like "Let it blow... it is under warranty and you would rather replace than repair". No kidding. I pretty much believed the engine was failing. I drove it maybe a mile or two and stopped in front of her house. Towed it next day to Ellis in Atlanta... a mechanic and service manager came outside and asked me to start the engine... the thing sounded like metal clanking to high heaven. There was no oil visible oil leakage. I don't remember if it actually turned over....Toast. During the engine replacement, the mechanic said he "didn't think it was the IMS". He showed me the oil filter and it was loaded with sparkling shavings.

The second occurred on an interstate doing about 60 MPH. No kidding, I was thinking about how well the car was running. Then the car jerked.. then resumed running fine for about 15 seconds then jerked hard again... at which point I threw in the clutch and drifted onto the shoulder... stopped the car and saw the engine had stalled. It would not turn over... just locked up. No visible oil loss. I had it towed to my indy... he said "classic IMS... it skipped time". He was wrong, the new owner pulled the IMS and it was fine...

Peace
Bruce in Philly

I think LN Engineering employees start these threads.

Its over blown based on Porsche shops I have consulted. Everyone they have changed is in excellent condition. 997 is a very successful, high production number car [I believe higher than the 996]. If the rate was high, it would be very evident. They ran the original larger style bearing in Cayman race series, not an LN bearing with no issues. It would be great info if someone life tested several engines. Is 125,000 to 150,000 typical life of this bearing?

In my opinion this 100-150K miles life expectancy is about correct, means it may be a smart move to give engine for rebuild about that mark, if it will last that long.

overall M97 design is a heck of an engineering marvel if those hi rev high performance motors indeed do last that long. people somehow expect those racing motors to last like they are diesels, it is quite unrealistic.

The issue lies in human nature and the cost of the problem if it occurs, however unlikely. When you tell people that there is a 5% chance (for instance) that their engine will grenade and cost them $25,000 to replace, you just scare a lot of people off. $25,000 is a large number, and I'm going to say that most people would not be able to come up with it in a hurry if they needed to.

With questions like this I tend to look at where the money flows - I wonder if there are any companies offering line item insurance against IMS bearing failures only. If the paranoia were that much larger than the reality, there would be a nice opportunity there. If nobody is taking advantage of it and it's not because of a law or some other force keeping them from doing so, it probably is a large enough problem for them to not want to touch.

This, plus the fact that there doesn't appar to be anything that an owner can do to prevent a failure. If my risk of failure is X% but I can drastically reduce that risk through routine maintenance, I may take that chance. But, it seems that the risk is actually X% and is almost completely random.

That's why I don't like to gamble. I don't mind taking risks if the reward is sufficient and I can miigate the risk through my own actions. I hate taking risks if the chance of failure is completely out of my hands.

As for systems that monitor the oil and sense metal shavings--well, that's a great idea for preventing catastrophic failure, but I still don't want my engine circulating shavings throughout the oiling system--even for a short time.

So nobody except Porsche has good data on IMS failures.

If that's true, and I believe it is, how is it that anyone can say that some 3rd party new bearing or "upgrade" is "better" than the old one?

What actual data does anyone have that a replacement bearing has a longer life or higher reliability than the bearing it replaced? Other than the assertion that the new bearing is "better"

What data has been provided that proves that the new bearing has fewer failures than the original bearing?

That's a fair question. What we know is that the IMS bearings prone to failure are not externally lubricated. They are sealed and contain their own lubricant, and when the seal happens to fail the lubricant leaks and there is no mechanism to replenish it. So the bearing fails.

LN managed to create an IMS bearing replacement that is externally lubricated, so the chance that the bearing would find itself dry decreases profoundly. Certainly the possibility of failure still exists; but the design is objectively superior.

To your point though, it would be interesting to see data on IMS bearing failures of LN or other replacement bearings versus the overall failure rate. I would be shocked if such data were attainable.

Now way bud, I thought everything you read on the Internet is true