street rod

Go to post #631 in this thread and you will see were I compiled all the available failure info by year model in the thread. You can generally tell what bearing the car had by the year model (in general 06 and later with larger updated bearing). More info would have been nice but this is all we had.

TV911

Thanks Street Rod! It's a long thread, and I didn't see your post. Here's a link... https://rennlist.com/forums/997-foru...l#post13015808

If I had the time I would pick up where you left off (researching any additional reported IMS failures). I have an '06 997 with an engine serial number reported to have the larger bearing, and I'm just trying to get a handle on the failure rate for that bearing. It looks like the evidence shows that it's extremely low. Of the 997 IMS failures, it looks like the vast majority are 05 models which probably have the smaller bearing. Porsche must have some data on this... I wish they would share it.

NIACAL4NIA

A defective bearing regardless of size is going to fail, however the larger bearing are much better than the single row bearings but upgrading cost is much higher

TV911

I hear you. My 2 cents... I wouldn't characterize the IMS bearing problem as being due to "defective bearings". It's more an issue of poor design. Porsche put a permanently lubricated (sealed, greased) bearing in a place where the grease gets washed out by engine oil, but there isn't enough fresh engine oil squeezing through the bearing seals to maintain good lubrication. Engine oil gets trapped inside the hollow Intermediate shaft, behind the bearing, and (according to Pedro) can become acidic. What little oil makes it inside the bearing is not ideal bearing lubrication. There is also the question of the loads on the bearing (vibration, drive chains pulling the shaft to one side). Under load, a smaller ball bearing is more likely to overheat and fail than a larger bearing. The lubrication issue can be improved in a couple of ways (pull the outer bearing seal off, add a direct oil feed system), but the load on the shaft may still be an issue for smaller bearings (which is why 911 owners upgrade them to double-row ball bearings, ceramic ball bearings, or plain bearings).

With the larger bearing, I wasn't considering a replacement or an upgrade, which would involve tearing the engine apart. I was only wondering whether it made sense to add a direct oil feed system. With the failure rates as low as they are, I don't think it's necessary, as long as I change my oil regularly and drive it hard every so often (no problem there!).

AdamIsAdam

I'm looking for a 997 (or 996). I'm trying to buy smart. I'd prefer a 997 but would like a serviceable IMS.

If I'm reading this thread correctly, early 997's may have serviceable IMS. I've also read that you really need to pull the tranny to know for sure. But is there a manufacture date by which the car/engine was made where there is for sure a serviceable IMS?

The 997 I just looked at has a VIN of WPOAB29925S741404. Build date on door says 11/04. There's also a decal on the engine bonnet that says:
"Webasto" (or something like that, the "W" is a logo that looks like this: (_)

It says 997.512.109.01
ID Nr: 17111988 (last two digits might be 66, it's blurry in my pic)
997 Coupe USA
Werker: 53
V-Lebenslauf: 10
Datum: 22 10 04

It's a Carrera S.

Any input related to early 997's would be great.

Feel free to PM if that's better than posting here.

TV911

The build date indicates that it most likely has the smaller, serviceable IMS bearing, but the engine serial number would be more helpful than the VIN number. You can see the engine serial number stamped on the side of the engine oil pan (looking from the driver's side of the car, in the back). Mine was a bit dirty and slightly corroded, so I cleaned it with a toothbrush and some citric acid, and then I was able to get a clean picture of it. I first shined a flashlight from the side to highlight the dots. Then I had to play around with light levels in Photoshop in order to see every number clearly, using multiple photos taken from different angles. My engine serial number is M96/0569607338

Then see https://rennlist.com/forums/997-foru...l#post14511481

I disagree with your analysis, though. I think you'd rather get a later model with the larger bearing. The failure rate of the larger bearing is extremely low. If you're still worried about it, you can drop the transmission, pull the outer bearing seal off, and install a Direct Oil Feed system.

bliq00

2006 Carrera S 87k miles no problems.

I also think you should look for an 06 or newer with the larger bearing. They have very few issues. or an 09+ if you can swing it. or a 996 turbo if you're into that kind of thing.

BHMav8r

Just changed my 2005 997.1 55k miles IMS last week. Had the old bearing sitting on my desk and noticed oil oozing out of it.

Sent this info and a pic to FlatSix, and here is their reply . . .


"You caught it just in time!
Your bearing is in advanced stage 2 failure meaning that the permanent lube inside the bearing assembly has been compromised and is diluted with engine oil. From here the next stage is when the bearing physically starts to shed steel from the bearing surfaces and when that happens, it is moments from disaster. There is no way to tell if it would last several hundred miles or even the next time you turned your key, bottom line is you caught it in time!
It would be fun to pull the seals from the bearing and inspect the internal components for early signs of damage. I am certain that the grease is destroyed, and I expect to see scoring or wear marks on the ***** and races. You may be really lucky if you find metal shards contained between the seals that did not get the chance to escape!
Jud Fink

Show original message



--
Jud Fink
General Manager
Flat 6 Innovations
706 219 4874 ext. 627"

TheBruce

Wow. Nice save. Didn't you originally bring it in for a clutch? Did they recommend doing both as standard preventive maintenance or were there symptoms of impending doom?

BHMav8r

Brought it in for a clutch. Was doing the IMS and RMS as precaution and "while you're in their.

Guess I dodged a bullet.

CMA

Hi Ricky

Any update on the status of your 997 S rebuild? I hope you are back on the road!

I am just collating every failure on this thread and it looks like yours is perhaps the only 2006 997s on here as having a failure. Was it confirmed as an IMS bearing failure as the cause?

Thanks

Craig

CMA

Hi All,

It has been about a year since a summary has been done. I have some time on my hands so have gone through and collated the data reported in the posts.

NB: I don't currently own a 911 but have been looking and obviously the IMS issue is something to consider. I have a bit of a statistical/research background so this is interesting to me in a few ways...

The findings from the summary back up all the current knowledge posted. Based on the information reported:

There were 320 posts on this to date from which there were 28 'IMS Failures' This is a reasonable sample but has some limitations based on self selection etc.

19% of owners of 2005 cars (22/115) reported an IMS failure... From the data posted I was unable to say if they were small or large bearings. This was a lot higher than I expected.

There are 3/108 owners of 2006 cars reporting an IMS Issue and 2/54 2007 cars. 0/30 2008 car owners reported an issue.


As to whether is is an 3.6 C2 or a 3.8 C2S was also interesting...

For C2s 8/74 had IMS issues/failure and for C2S there were 12/200 IMS failures.

As for milage at which failures occurred these were reported to be between 10,000 - 75,000 miles at an average of 42,000 miles and 44,000 miles.

So does this mean anything new? Probably not...

1. If you have a 2005 car you should probably get the retrofit. It doesn't matter what milage it is at.

2. IMS problems can hit both the 3.6 and 3.8 motors.

3. Although some reported issues in 06 and 07 cars these are pretty rare.

Hope that helps others! Any questions on the data please ask.

Craig

TheBruce

Craig, you rock. We were just having a convo on whats required to make this data more relevant in a poll on PDK failures.

My position is sharing this data is a fantastic resource but these polls are so statistically invalid they are doing more harm than good. There is a massive self selection bias in these samples, large margins of error, incorrectly formatted questions (e.g. the 997.2 doesn't have an IMS but is included in the survey), etc, etc.

The bore scoring poll and new PDK poll have issues as well.

Do you have ideas on how to create a guideline for forum surveys?

BHMav8r

I'll second that.

Thanks Craig

Petza914

That statement should be clarified and written
1. If you have an early 2005 car with the smaller IMS bearing, you should probably get the retrofit. It doesn't matter what mileage it is at.

Both of my '05 C2S cars have the larger, non-serviceable bearing. From the data I've compiled, the engine serial # cutover from the small bearing to the large bearing are as follows:

3.8L motors, up to M97/01 68509790 has the smaller IMS bearing and Engine number from M97/01 68509791 has the larger revised IMS.

For 3.6L motors, up to M96/05 69507475 has the smaller IMS bearing and Engine number from M96/05 69507476 has the larger bearing.

My 2 engine Serial #s are: M97/0168512123 & M97/0168512680 both after the 3.8 cutover from small to large bearing, and visually confirmed with a transmission pull during the PPIs.