Mspeedster

Since the class action settlement has caused the IMS issue to make the headlines once again, I decided to check on the accuracy of the "YES" responses in the "IMS failure for your 997 car, Y or N?" poll.

I have pain stakingly checked on each rennlist poll participant who checked yes and the result is quite eye opening. Many of the folks who voted "yes" don't even own a 997!!!


Of the 37 "yes" replies as of July 28, 2013, only about half are valid IMHO.

I would break it down into the following groups:

Group 1 - Confirmed or probable 997 IMSB failure number: 18
- 16 of the 18 are MY05 997 cars, 1 MY06, and 1 MY07
- As the poll is really suppose to be about 997 failures, in my view, only the "yes" replies given from Group 1 are valid.

--
Group 2 - Confirmed or probable non-997 IMSB failure number: 7
- 5 996 owners, 1 Boxster, and 1 Cayman

Group 3 - Suspect, unconfirmed or second hand "yes": 4
- After exhaustive searching, I could find no evidence to indicate these folks really experienced an IMSB failure. One person seemed to be a Porsche indy and perhaps provided a second hand "yes". The rest I consider "suspect" or "unconfirmed".

Group 4 - Mistaken "yes": 2
- Two people in the poll admitted to wrongly answering yes

Group 5 - Spoilers: 6
- These are folks who seem to have no record of ever owning a 997 (or 996 or Boxter or Cayman) and voted "yes" for the heck of it. Most are 993 owners.

gpjli2

"16 of 18 are 05 cars". This is what I had questioned a year ago and should put this in perspective both for early model owners and those w updated bearing. Thanks M. I know this has been a true labor of love for you.

alexb76

Why is it surprising? It's the most unscientific and least accurate sort of polls you can imagine.

Based on REAL data, around 3% of ALL M96 engines from 2001-2005 have had this failure, AND all cars built post March 2005 have the upgraded IMS that doesn't have this issue.

I think that's basically sums it up, case closed!

997_rich

Yes- M speedster, I've been occasionally doing the same calcs as you and contacting the people who have had failures.

For groups 2, 3, and 5 I've contacted a number of them and received a response that many of them own multiple cars or have since switched cars since the failure. So very difficult to get a truly accurate account.

This poll was never intended to be a truly scientific poll but when I started the poll, there were some people saying that 50% of 997s were failing or 1% were failing. Clearly, neither of those are the case. The poll is also biased because it's polling enthusiasts (people who are involved with a car enough to spend time on the computer talking about it). Those people MAY have use patterns that may cause more failures etc.

What can we scientifically conclude from the poll?: Not much. It's likely but not proven that the failures for 997s as a whole are less than 5-6% (probably more like 3-4% and there may be extenuating cirmcumstances that cause many of those). The m96 engined cars are more likely to fail than the m97 cars.

I'm pleased though that at least now we have some sense of what we can expect as 997 owners.

DreamCarrera

+1,000,000,000,000


These IM$ polls(997, 996, etc.) are pure BS. All of them have seriously flawed numbers for one reason or another and because of this serve no useful purpose. The only thing they really accomplish is to further devalue our P cars by scaring the living daylights out of prospective P owners who come across these polls in an internet search.

The mods should delete ALL of these polls!!!

Sporty

Just to clarify - the 997 engines with the smaller bearings, mainly early build 2005 997's are more prone to failure, whether an M96 or M97. My engine is an 2005MY M96 with the larger revised bearing -so the blanket statement of M96 vs m97 is more prone to failure is inaccurate in of itself; the frame of reference should be older style bearing vs revised bearing typically found in late build 2005 997s. Furthermore, if one is to believe the discovery info as a result of the class action suit, those findings indicate less than 1% failure rate on the larger revised bearing vs 4- 8% for the smaller bearing. So non late build 2005 997s could be subject to 4-8% failure while the rest is less than 1% FWIW.

perfectlap

except that those m97 IMSB's aren't ever coming out for the vast majority since the cost of doing so will be an engine-splitting, out-of warranty expense. This creates a flawed logic that since the bearing was excellent during its 'shelf life' that this necessarily means it will be excellent beyond that bearing's 'sell by date'. What's the plan B for 997.1 with a non-serviceable IMSB come bearing-swapping time? How will that affect the IMS failure rate long-term if the vast majority of these cars are not addressed due to the very high cost?

All serviceable bearings, particularly a sealed one inside of an engine, should be replaced at a regular interval -- mechanical engineering logic. Even if you remove one of the seals to allow for more oil flow, the m97 bearing isn't going to last forever. I fail to see what is going to keep those single row bearings in place once the supports have eventually become compromised, and they will.

With the 'more prone to failure' m96 IMSB extraction is a simple, extremely cost-effective procedure whenever the clutch is replaced. Or even even better, it can be eliminated altogether like a 997.2 via the LNE Solution, also a more cost-effective procedure than engine-splitting.
Seems to me that much like a clutch, all m96 and m97 cars will need their IMSB replaced at one point or another, yet only only the m96 IMSB cars will have done so in large numbers.

p.s.
IMSB is not the only issue with the m96 and m97 engines that scare people into holding out for a 9A1 engine once depreciation has set in via mass production. So let's not say that IMSB hysteria is the culprit.
These first generation Porsche water-cooled engines have many ways of failing long before the mileage gets into the high mileage territory.

mgordon18

Just to be clear - the m96 and m97 designation has no bearing [heh] on the IMS bearings used. There are old-bearing m96s and new-bearing m96s, as well as old-bearing m97s and new-bearing m97s. The m96 engine is in the base car (325hp). The m97 engine is in the S car (355hp). The switch from old bearings to new bearings for BOTH engines came on or near February/March 2005.

Saying "m97 IMSB's aren't ever coming out for the vast majority since the cost of doing so will be an engine-splitting, out-of warranty expense" is an incorrect statement. There are pre-Feb 2005 m97 engines that have the old bearings that could come out and be replaced the "easy" way.

Your sentiment IS correct though, but you should say, "upgraded IMSB's aren't ever coming out for the vast majority since the cost of doing so will be an engine-splitting, out-of warranty expense."

Just trying to keep the terminology correct, since this has been a point of contention in the past.

perfectlap

yep. I forget that there are m97 engines with m96 IMSB. Although there must be very few of these, must have been a factory call -- use what you got Heinz, zee new stuff is on zee way.
M96 engine with m97 IMSB is like worst of both worlds as far as out-of-warranty ownership is concerned. Unless these were in-warranty 'do over' engines, there must not be many of these either.


Either way, the poll is flawed because m97 bearing cars, as a whole, have not hit really high mileage yet. The original bearings in those cars are still within their limited shelf life period.

Mspeedster

+1

FYI - For those who didn't currently own an IMSB engine car, but may have switched cars, I looked for their postings related to cars with IMSB engines as clues. Those with a posting about a failure, I put into Group 1 or 2. Those that had absolutely no posts relating to an engine problem, I put into Group 3. However, there were some who seemed never to have owned an IMSB engine car, as 98%-100% of their posts could only be found in the air cooled forums and not a single post in a water cooled forum. Many were mainly only in the 993 forum. These I classified as Group 5 - Spoilers. (I suspect some are 993 bigots who may want to see their 993 values increase at the expense of further tarnishing the 997's good name.)

Sporty

"M96 engine with m97 IMSB is like worst of both worlds as far as out-of-warranty ownership is concerned"

Why do you say this Perfectlap-what is the difference-both have the improved but not easily serviceable bearing? For the third time, the bearings are not distinguished as "M96 IMSB" or "M97 IMSB"

mgordon18

I think some are calling the upgraded design the "M97 IMS bearings." I get what they're saying, but in fact, the M97 engine did not supersede the M96. They were being built concurrently throughout their lifespans. So unless there's some nomenclature that I'm not aware of, there's no such thing as an "M97" IMS bearing set, especially one that exists in an M96 engine. It's just the new kit or the old kit. "M" number shouldn't have anything to do with it.

perfectlap

Nevermind I misread MGordon18's post. My original point is that m97 engines (produced after the early 2005 switch (as MGordon18 points out), are very unlikely to ever undergo bearing maintenance. A 1% bearing does not equal an ever-lasting bearing.

The stats they cited were of internally reported failures. As in the cars that Porsche were monitoring in-warranty, or cars that came to them out-of-warranty begging for good will engine replacement. So right there those numbers, as they stand now, may be skewed/are unreliable, the failures could be much, much higher.
BUT -- since the old bearing is indeed serviceable and thousands have been proactively replaced with routine clutch jobs after only 2 or 3 years, by independent shops as well as a growing number of Porsche service departments, one could argue that it has become a standard part of clutch replacement. The IMS risk strictly speaking, with old bearings boils down to the owner's timing, will he get his car in for clutch replacement before the IMSB goes down? The odds seem decidedly in favor of the owner.

Meanwhile those with non-serviceable bearings (late 2005-2008) may be buying into a false sense of confidence since lower mileage for these cars, as well as lower production numbers, may be affecting the low 1% failure figure. Where the old bearing cars could reduce their failure numbers each time a clutch/IMS was replaced -- a routine practice, the m97 non-serviceable bearings will not have this benefit. With each clutch job that is done on an m97 car the likelyhood of a IMSB failure will not stay at the current alleged 1%. It could feasibly exceed the plaintiff's alleged failure rate of the old bearing cars, (as well as the accurate failure rate). I have to think that the average 997.1 owner will sell his car for a 9A1 997 or 991 before paying to split open the engine. Which begs the question who is ever going to to foot the large bill to replace the bearings in these cars before the IMS fail on their own?

utkinpol

ity is difficult to speculate about that but for an 'average' customer it is probably correct.

I think as those 997.1 cars with both m96 and m97 motors will start coming to a mileage mark of 100k miles more and more issues will be posted. what will fall apart first there is a good question, if anything, will it be D-chunk, or IMS, or chain tensioner, or ... - who knows.

it is same as it is for 996 cars or 993 cars - at some moment maintenance becomes a major pain and engine refresh/rebuild is one of such tasks, in my opinion. and with M9x motors this task is simply not optional.

when you asked of 'what to do about non-serviceable IMS bearing' - typical approach is to remove dust seal on the outer side when you drp gearbox down to improve lubrication OR at same time you can add direct oil feed to spray oil into the bearing to improve lubrication even more. some say it should prolong life of the bearing significantly enough.

I did not do either thing yet. Still thinking of what to do next, but most likely I will commit to engine rebuild or replacement in some future time like most people do, probably at 100k miles mark.

Sporty

Note that as we speak another option is available and another being worked on. Flat 6/LN Engineering is trying to figure out how to extract the bearing w/o splitting the engine, while another reputable florida outfit has the dirict oil feed system retrofit, and another is working on a roller bearing (although not sure if applicable in the 'revised' bearing case). Not sure how proven any of these are at this point, but in a year or so we may have more viable options. Other than that, if the worse happens you can plead the case to Porsche if you have not altered anything and serviced accordingly, especially in light of the class action suit related to the 'smaller bearing' failures