I was a little bored tonight and I spent some more time trying to track down information on IMS failures in M96 engines.

First, I have to admit the engine designation, M96, can get confusing. As far as I know the M96 engine has many derivatives in the Boxter and 996. Later Cayman and 997S engines are actually M97 engines but are basically M96's in general design. However, I am not positive on this. Either way, both the M96 and M97 have IMS's. It appears most IMS failures have taken place in early M96 engines and have dropped off significantly as the IMS has been upgraded by Porsche.

I spent some time researching the subject before I purchased my 06 997S. As always, online chat forums tend to over amplify a problem. In forums its easy to get the impression that 50% of M96 engines suffer from IMS failures. In reality, based on the many articles I have read on the subject, I would say the percentage is closer to 5. Meaning, 1 in every 20 M96/7 is going to suffer from some kind of IMS failure. Still not great numbers but most likely more in line with average engine failure percentages for most cars.

But can the chances of IMS failures be reduced even more? I have seen replacement IMS kits for the 996 and early Boxters before and have found the companies that make them to have some of the best advice and data that I have seen. I am still unclear if these over engineered IMS upgrade kits have applications in MY06 and later M97 engines but I figured I would post some of this information since I rarely see this subject addressed any deeper than, "make sure you have a CPO"....

I have said several times that treating your Porsche like a garage queen is most likely having the opposite effect most intend it to. Hence why I have also said several times, "a redline a day will keep the engine failure away." The linked website and article provides a much more detailed explanation as to why this is the case with our engines.

Here is a quote, "Higher rpms also increases bearing life as this lessens the viscosity requirements of the lubricant to maintain EHD lubrication, also providing a reasonable explanation of the lack of IMS failures in tracked cars or those driven "like they were stolen." Likewise, far more failures are found in engines with low mileage that are garage queens and never driven to their full protential. Further recommendations by the retired Timken engineer are evident in the design of LN Engineering’s IMS upgrade and retrofit kits."

LN Engineering's data and IMS replacement products appear to be the most popular kits produced and I have even seen articles concerning them in Excellence ( I believe March 2008 ).

In a nut shell...

From what I have gathered from the various articles I have read. The duel row IMS bearing that is found in most M96 engines and MY05 M97 C2S engines is the culprit for most failures. MY06 and later M97 engines received a much beefier single row IMS bearing. While it appears there are replacement options available, they are costly to install due to the new design. Without completely replacing the IMS some of the best advice I have seen is,

-Get frequent oil changes
-Drive the car the way it was designed to be used
-Get frequent inspections in order to catch an impending failure before it occurs.


My intention with this thread is not to promote more doom and gloom about IMS failures but actually shed some light onto the actual failure rates and how to prevent them.

Also, it appears there is a way to mitigate the risk if anyone is thinking of buying a 996 or M96 engined Boxter.

Here are some good links for those interested.

http://www.flat6innovations.com/savi...e-ims-retrofit
http://www.lnengineering.com/ims.html

Jason

 

Definitely hard to pinpoint the exact failure rates, but from my research, I'd have to concur with you that it's around 5%.

Thanks for taking the time to post. In the future, hopefully those considering a car with the M96/early M97 will search and find this thread, and be better informed as a result.

 

Excellent information. Thanks for taking the time to provide it. I'm forwarding it to several concerned friends who it applies to.


John

 

My 2002 daily driver 996 which was driven 12K miles a year had it . It was fixed under warranty and there was no damage. I drive the car another 6 months or so with no issues after the repair .

 

How does one inspect for the problem? What are the warning signs? And what would be the approximate cost or a preemptive replacement? BTW 5% sounds like an incredibly high number - from a (Porsche) financial perspective. At that figure, does anyone have an estimate of what this cost them (under warranty)?

 

Here's what happened with me -
The car ran fine and one day I backed out of my garage to see a few drops off oil . I brought it in for service and was told "rear main seal" . Keep in mind that this was back in 2002 and I had not heard of RMS at the time . In fact the part had to be ordered and it did take some time (I don't recall how long) . It was fixed as soon at the part arrived and no more issues .

The big dilema comes with the owner whose car is out of wararnty and he fails to notice anything wrong . It's not a cheap fix . Since its mostly the used car buyer who faced the largest repair expense one can imagine that the financial impact was greatest felt by the segment who needed to save the most . Hence the internet forums opened up many discussions where this engine flaw was talked about at length . In fact an out of warranty 02 996 probably isn;t the best selling used porsche and RMS might be factored into that.

 

Read the article I posted. It answers your questions better than I could. However, if you have a MY06 997S or later the replacement requires that the engine is dropped and then disassembled to get to the bearing. Probably very costly and not worth it IMO since the bearing is already beefy.

5% is not good but not really that bad either. Again, we are talking 1 in 20 cars and the solution could be as simple as avoiding long intervals ( 15K like Porsche recommends ) between oil changes.

Jason

 

Did you have an RMS failure that led to the Mech noticing a failed IMS and thus you had the IMS replaced?

Or are you saying you just had an RMS failure? To be clear an RMS failure can lead to an IMS failure but they are two different things. Also, RMS failures are much more common, but less serious, and occur on all Porsche flat six engines including the GT1 derived engines in the TT's and GT series cars.

Jason

 

It's hard to remember 4 Porsches ago but if my memory is accurate the RMS seal and IMS bearings are related . A bearing can wear out if not lubricated (oil) . My car was making the famous rattle of IMS but since it was so long ago I don;t have the paperwork to look up all the parts .

I caught the problem on the very first drops of oil. It woild be easy to overlook . If one listens to music even the rattle might go unnoticed.

 

RMS doesn't really worry me too much - oil is very cheap compared to the RMS replacement but IMS is a worry.

Thanks for the informative post - definite +rep to the OP!

 

Thanks for the excellent research and much appreciation for the links.

 

Jason,

thanks for the post and taking the time to write it. I believe that the above statement you write is the general consensous. Very concise and too the point. And as someone who has had the older engine replaced with a newer one I feel better about my chances.

However two points...

first it's boxster, not boxter.

second, and we have been thru this before on RL: I believe the 5% figure is pure speculation. No one knows the exact number. No matter what the articles say.

No one could possbile know over the life time of the M96 engine worldwide how many have gone south due to IMS. They can only guess.

It may comfort someone to see that number but IMHO its worthless.

No one really knows except Porsche.

 

I believe there may be some confusion between the IMS issue and the RMS issue. The latter is a basically a nuisance and costs about $1000 to fix/replace the seal on the crankshaft. The IMS issue is far more serious. It it fails ( without warning!) you're basically talking about a new engine (catastrophic failure). A redesigned RMS has greatly minimized that problem. The IMS was redesigned in 2006 with a larger intermediate shaft and nut. Excellence had a great article on this.

 

A true IMS falure necessitates a new replacement engine. I have heard between 13-18K.

 

Spot on. Been there.

Going 65-70 on the turnpike , hear a noise and then the dash lights up like a X-mas tree and you limp (luckily) into the shoulder.

I do feel better with the redesigned engine in car.