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We all live with the possibility of IMS failure. Many more stories are told here of cars that had issues than of cars that haven't. It seems that the general consensus is that there is a possibility that your 996 engine will self-destruct with an IMS blow-out at some unknown, unlikely, unsuspecting, and certainly most inconvenient time. Or, it won't.

After much thought, and even a little loss of sleep, I had the retrofit IMS work on my C4S.

IMS, RMS, clutch kit, pilot bearing, water pump, thermostat.

I must admit that I'm one of those who firmly believed that an IMS failure would never happen to me. Ignorance, they say, is bliss.

And I will admit to a sense of relief now that the work has been done.

The cost of a prophylactic generally seems to be money well spent. Considering the possible consequences. Others have said this. I'm a believer now.

Edited by judgejon
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OK, Yer Honor -- how much did it cost, all in? Many of us have the same worries. (Me: 54k mi on '04 C4S Cab).

$3700 total.

My trusted inde had the car in his shop for a week.

I'm hoping that the moral of the story is "a stich in time saves nine."

j

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Given the inadequate lubrication that the m96 IMSB is subjected to, I think you were wise to replace your bearing. Lucky for you that your engine was eligible for the retrofit--not all are. Did your independent mechanic do some expectation setting with you regarding the replacement bearing and its lubrication?

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  • 3 months later...

First post to this most excellent forum! Previously owned '81 924 Turbo (bought new when I was young & single!), and '89 928 S4 bought 1993 and sold in 1997. So I've been without for many years until my recent purchase of a '03 996 C2 cabrio (which required significant negotiations with the wife as we have 3 in college now!). I've had it now for about a year and am most assuredly a 911 devotee! I'm the 3rd owner; the 2nd owner bought it as a CPO and blew the engine, which was replaced by the Porsche dealer with a 2005 engine in April 2007. There is now approx 12,500 miles on the '05 engine. I've been reading about the LN IMS retrofit kits also, but does anyone know how I can tell if my current '05 engine has the 13mm or 22mm IMS bearing nut, as the way I understand things the 22mm size can't use the LN retrofit?? As an aside, the latest (Dec 2011) edition of Panorama Tech Q&A section discusses 996 IMS bearings with Mr. Reiser stating "the LN Bearing Retrofit kit is a must on all 996 models".

Thanks for any assistance & advice!

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I'm not so sure I agree about that "must" comment...

But if your engine has the larger 22mm bearing the engine must be torn down to retrofit (and according to LNE every 50,000 miles or so as it is being deemed a "service wear" item).

Perhaps the IMS Guardian is a better alternative.

As for whether or not yours has the bearing or not, 2005 engines are the first year those bearings started showing up, but some of that might depend on what month.

If you post your engines serial number perhaps it could be decoded and compared with another engine's sequence number that does have the revised Porsche bearing.

Aside from the above, the only certain way to determine bearing type is to remove the transmission and flywheel to inspect the IMS flange and center nut.

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I followed the advice of many on this forum and replaced the IMS when my clutch started to go last December. MY99 996 CAB

Here's the breakdown of expenses.

IMS bearing $619 - came with free RMS (saved $30) because I used LN Engineering online store

Clutch kit Sachs (EBAY) $450

Resurfacing of existing flywheel $90

Flywheel bearing (generator bearing) $20

Labor - $940 Fremont Foreign Auto recommended by Parts Heaven in Hayward CA - the owner Eduardo knows his stuff and owns a Porsche.

Total $2119

My car has 42k miles and the IMS bearing, for what its worth, was in excellent condition. However, there was oil weeping from both the IMS and RMS according to Eduardo (the car never leaked on the garage though). Eduardo always replaces the RMS when he does at clutch job at no extra charge.

Bottom line is no more IMS anxiety and I feel my car is worth more now with the new uber bearing. Also, the clutch and resurfaced flywheel is a huge improvement in the car's performance. The new RMS is a freebie.

Edited by ltumacder
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Have there been any details from LN or people who have had the LN bearing fitted and have now reached 50,000 miles on it. I had mine done a year ago and wont reach 50K for a while yet but it would be interesting to know how they are performing towards the end of their suggested life span.

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If you read through LNE's IMS web page they have recently updated it.

On the single row engines (some 2000-2001 and all 2002-2004 cars) that have been retrofitted (and are apparently more prone to failure), have had 3 known documented retrofit kit failures.

"It may be advisable to consider the IMS a service item, like a timing belt in many modern cars. Seeing that we started to see more MY05 engines with IMS failures in late 2009 as well as failures in MY06 (with revised 3rd gen bearing) in late 2010, that may suggest that bearing replacement (or inspection at bare minimum) should be considered as part of the normal maintenance every 4-5 years or 50-60k miles, maybe even sooner with the case of the single row bearing."

http://www.lnengineering.com/ims.html

Edited by logray
  • Upvote 1
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I'm not so sure I agree about that "must" comment...

But if your engine has the larger 22mm bearing the engine must be torn down to retrofit (and according to LNE every 50,000 miles or so as it is being deemed a "service wear" item).

Perhaps the IMS Guardian is a better alternative.

As for whether or not yours has the bearing or not, 2005 engines are the first year those bearings started showing up, but some of that might depend on what month.

If you post your engines serial number perhaps it could be decoded and compared with another engine's sequence number that does have the revised Porsche bearing.

Aside from the above, the only certain way to determine bearing type is to remove the transmission and flywheel to inspect the IMS flange and center nut.

In response to the above, here's my replacement engine's serial #: 03AT66566755

If anyone can determine if this has the 13mm or 22mm nut I'd be HUGELY appreciative.

Thanks!

Edited by SWODOC
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Check out this thread.

http://www.renntech....engine-sn-help/

His engine has the larger bearing that can't be replaced without complete engine tear down and sequence number of 66526, which is earlier than yours 66755. Both of which are greater than the sequence number range to 60000.

M96/01AT66X66526

Chances are your engine has the larger 22mm bearing.

However the only REAL way to tell is to look at it, with the transmission and flywheel removed.

Having the newer bearing is not necessarily a bad thing, as its stronger than the single row in most 996 cars and about as strong as the original dual row bearing in the 1999 and 2000 models.

Chances are good that it could last the lifetime of the car.

Edited by logray
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A correction to my post above, your replacement engine 03AT66566755 was built in 2005 but it is impossible to say when after that it was remanned, without having access to Porsche's internal database.

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I do not suffer from "IMS Bearing anxiety"....have never replaced mine.

Some comments from people that have replaced the original IMS bearing:

"Upon removal the bearing was found to be fine, but now I have piece of mind"

"My removed bearing was in perfect condition, now sits as paper weight on my desk, but now I have piece of mind"

"My bearing was OK, now I have a new part in my spare parts collection, but now I have piece of mind"

I know at least 5 guys with 99 996's with over 100K miles with the original IMS. Go look at many of the roll calls "how many miles on your 996?"

Mind you, IMS failures AND/OR intermix failure DO happen, BUT IMS failures have been marketed a lot more, since people are making money from "preventative measures". Hence it is in their best interest to instill fear and promote failures (even if it is another kind of failure they are blamed on the IMS).

And when a failure happens to a car with a new IMS: well, we do not know if something else failed, and took out the new IMS bearing.

Then couldn't it be that the same thing happen to all the "previous IMS failures?"

I hope readers can catch my drift........

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The original dual row bearings in the 1999, 2000, and some 2001 cars don't seem to have as many failures from what we're being told.

It's too bad there's not some mandatory database where these failures have to be entered so we could see some real statistics.

"However, of all three revisions of the intermediate shaft used by Porsche, the single row bearing found on some 2000-2001 and all 2002-2005 models is the most flawed" from http://www.lnengineering.com/ims.html

Also I've seen Jake and Charles mirror this in the forums, that they tend to see the most failures in the 2002 ish models with single row bearings.

No doubt there are plenty of single row cars on the road with over 100k as well...

And I would disagree that at least most people seem to do their due diligence on failure analysis and not just blame it on the IMS.

"and even with our ceramic bearing, we have had three engine failures where the single row ceramic bearing was found to have failed" from http://www.lnengineering.com/ims.html

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Continue the sentence and you will find the Disclaimer:

"and even with our ceramic bearing, we have had three engine failures where the single row ceramic bearing was found to have failed"......

....(although not conclusively as the cause of the engine failure , given there are dozens of known modes of failure and secondly, these are open bearings susceptible to damage from foreign object debris)."

By not conclusively, it implies:

- The failure may have been caused by something else, not the IMS

- Clearly states there are dozens of known modes of failure (dozens, as in 24, 36,48, 60.....not just the IMS bearing).

- BUT there is a preventatice fix for ONE of the DOZENS (24,36,48,60?), and the part alone costs over 600.00; Go figure, as much as a clutch kit !! (I estimate a manufacturing cost of 35.00 for that bearing, if that much).

- The 3 failures do not mention how long (in miles) after the installation the failure happened, how many miles the engine had when the new IMS bearing was intalled, who installed the bearing, were they track cars or daily drivers?

What I interpret of the whole paragraph:

It is unknown if the IMS failed or something else made it fail (whether it is the LN Engineering bearing, or the original that came with the Engine).

Now, I would never knock someone from buying and installing the bearing for piece of mind, my piece of mind have value as well.

It is just that after I look at the facts, this IMS issue appears to be more market hype than actual evidence. This is my personal opinion, and that is why I sleep well, and do not think about my IMS failing, as the experts state: "there are dozens of known modes of failure".............

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I believe some of it is hype as well.

But I also think they've also produced some compelling information to show that it is a real design issue in this engine.

If you spend enough time on rennlist you'll read that Raby regularly sees multiple cars per week come in due to IMS failure, and others who have had their engies replaced by Porsche.

In addition (as a response), Porsche has a.) increased the bearing size in later engines and b.) eliminated the design from their newest engine. B alone by itself is nothing out of the ordinary as car makers do often redesign engines. Look at the Porsche turbo and GT platforms and the engines that they are based off of.

Even the above though, as you point out - you read about the "crap" on the internet and not as much about the success stories.

About the only statistic I've seen (from that same website above) is that as many as 10% of cars will experience a bearing failure in 90,000 miles. The problem is, that's only an "estimate". Coming from a retired bearing engineer, I'm not sure whether that could be classified as an estimate or a guess. Does he have enough experience with automotive bearings and failure analysis to warrant being an estimate?

At the end of the day though there are cars who have suffered IMS bearing failures, but no one has any "solid statistics".

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logray,

Well stated......thanks for a solid and factual response......

I recently replaced my clutch (at 50K, now have 60K), did not even bother with the RMS and IMS (neither was leaking). I drive the car plenty (average 15-20K a year). It is almost a daily driver

When the next clutch change comes (2 years?); I will remove and replace the bearing (more out of curiosity than concern, in any event, chances are I will have one of the other dozens of failures), by that time Pelican Parts will have their own version for about 150.00 bucks.

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just picked my car up Friday with new engine after IMS failure. Service advisor said there 2 cars that also had IMS failure just after mine came in... one was a 2002 like mine, I believe the other was a boxster... total for mine was $24k, I had a $100 deductible :)

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For logray: Thanks for taking the time to look into my replacement engine serial #. Like many others on this thread, I too am not losing sleep over the issue. This is my sunny day car (and there are typically plenty of those here in FL) and I usual run it pretty hard on the back roads....I'll just keep enjoying it!

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