mjberning

As a Aerospace Engineer I have not seen any root cause analysis done to definitely prove whether the problem is an issue with the oil seal or the inability of the original bearing to sustain the loads and temperatures inside the engine.
I would also like to se the hard dat and not just a lot of conjecture by all of the enthusiasts.

Im fairly convinced the failure rate stats cited by solution sellers are largely based on anecdotal evidence and number of replacements done. I performed a cars.com search on Porsche 996 vehicles for sale and came up with 6.2 % of all P 996s listed having IMS replaced. If you search just on P 996.2 that percent is a bit higher. I got the nearly the same results looking on auto trader.com. Most of the IMS upgrades were preventative so you will never know the actual failure rate of the OEM bearing. I also noticed many P 996 owners seel their vehicles shortly after performing the upgrade. What does that say about the upgrades? I am curious to know why so many owners sell their vehicles after upgrading. I spoke to one when I bought my 996 and he told me he decided he wanted a 993 instead. Did he get the upgrade to improve the resale value or did he not trust the upgrade as being better. He showed me the original bearing at it was intact and appeared to be normal.

An engineer would ask what is the operational requirements of the bearing and what are the specs of the different solutions?

Minimum and Maximum Temperature
Maximum Internal Pressure
Maximum Revs
Maximum Radial Load accounting for 6 Sigma Dispersions
Maximum Axial Load accounting for 6 Sigma Dispersions
Worst Case Oil environment?


If its a oil seal issue why does someone not offer a bearing with a seal that will not leak? We build ships that do not rust in the sea. Surely we can build a bearing that can sit in a vat of slightly acidic oil for 3 years. Why not plug up the hole in the IMS shaft so Oil does not build up in it and blow thru the oil seals?

I just see a lot of conjecture out there by internet bloggers hyping the problem but Id like to see a table comparing the specs of the different solutions the operating environment requirements for the bearing. That would help owners decide whether or not the solutions are really any better than OEM and worth the investment.


Solution Max Temp Max Rev Max Radial Load Max Axial Load Seal Acidity Tolerance Max Seal Pressure
LNE
EPS
OEM

5CHN3LL

I don't have an opinion, but I can confirm that at least one indy shop in San Diego is installing the Vertex bearings in at least some cars they retrofit - I was in the other day to see if they had any customers parting cars out (trying to score some factory wheels), and I noticed they had a box full of them on the workbench...this is a very old-school shop that deals mostly with air-cooled Porsches; when I took my Boxster there 5 or 6 years ago, they had barely started working on m96-powered cars.

stasha

Excellent analysis of the validity and preponderance of the evidence.
While the anecdotal/case reports of failure of the IMSBs definitely feels above the norm, people typically confuse anecdotal stories and individual case reports as being "strong" evidence -- whereas it is the weakest form of evidence.

This is common in Medicine, and it accounts for the numerous gobble-dee-gook cancer remedies that somehow gain traction on the Internet.

Are you planning on pursuing this?

Weazer

Hello All, longtime lurker here, have a 1999 996 Cab (Ocean Blue Metallic/74k mi) and a 1999 Boxster base (Arctic White/78k mi). Recently did clutches, pressure plates, throwout bearings and RMS' on both cars, and installed the EPS Cylindrical Roller Bearing on the Boxster. Uneventful installation, however, the original dual row IMS bearing was very wobbly! I change the oil at 4k mi religiously and cut open the oil filters after each change, I never found any ferrous metal on either car, just the odd piece of black/brown plastic from the chain tensioners. Word to the wise, the dual row bearings do fail! I had a false sense of security because both cars were 99's and supposedly had the more robust dual row bearing, so I was real surprised to see the state that the Boxster's bearing was in. Wanted to do the cylindrical roller bearing on the 996 as well, however, the IMS cover had the large 22mm nut on it indicating a remanufactured engine with the larger single row bearing that cannot be extracted without splitting open the cases. So, i removed the IMS bearing's oil seal and buttoned it back up with a new seal on the IMS cover. I'm an ex-machinist from the Philadelphia Naval Shipyard and had confidence that the cylindrical roller bearing would solve the IMS bearing issue once and for all. Car is running sweet, and I have peace of mind driving it. EPS has come up with a solution for the "captured" larger single row IMS bearings where they bore out the engine case to be able to extract the bearing and insert their cylindrical roller bearing, but I think they only do that in house at their Florida location. Apologies for the long post, especially for a first timer, I will never bother any of you again! P.S. Much wisdom on this board, Jake/Flat Six and JFP in particular, how lucky are we to have 2 such experts sharing their thoughts with us?

5CHN3LL

Both comments are true - and those of us who would actually like to quantify the issue have long since given up. Nobody who has numbers is sharing.

RE: your analyses of cars for sale - it's a valiant exercise, but they're data points that may - or may not - have ANY resemblance to the overall statistics. Maybe people who have their IMS bearings electively replaced are also 70% more likely to sell their Porsche within three years. Maybe people who have never heard of the IMS bearing are 50% less likely to sell their cars. *shrug*

The only semi-solid data points I'm aware of were the sales stats for M96-powered cars and the data offered by Porsche during the IMS class action. That latter point, which was vague at the time - is now years out of date; the numbers might have been representative of reality at the time, but we're now years further down the road.

TL, DR: Yeah, we'd all like that info, but it doesn't exist.

Flat6 Innovations

Its not, and never has been a matter of lubrication. I knew that almost 15 years ago.

IF it were a problem with lubrication, the dual row IMS Bearings would fail MORE often, since they require TWICE as much oil volume to stay cool and lubricated.

This is NOT the case, as dual row bearings are the lesser of the evils, which was even substantiated by the statements Porsche made during the class action suit where the dual row bearings failed less than 1% of the time, and single row failed 8% of the time.

jaetee

I have the Vertex Eternal solution with cylindrical bearing and direct oil feed (via the slotted hex drive shaft) installed in my car. At $450 (Amazon) for the kit, both my mechanic and I felt this was an elegant, cost-effective solution to this problem that really shouldn't exist... The original bearing that came out of the car (at 93k) was still in perfect condition.

The work was done recently so I don't have long time feedback to offer just yet, but the car is running fine. Clutch, RMS, chain tensioners, AOS, water pump, t-stat also done. I also switched to a magnetic drain plug to monitor things... I'm driving the car with piece of mind, but a fair measure of restraint when it comes to RPMs for the foreseeable near future due to the extensive amount of new bits installed. So far, so good.

mikefocke

There is no statistically valid study that would give us the answer of what bearing to use.

Quantity 1 anecdotes aplenty but all self selected and self reported which leads to bias.

There must be 20 different bearing packages offered all over the world.

Select one where there are instructions that everyone acknowledges work. Be mindful of any special tools that must be bought/rented/built to do the job. Ask how many the installer has done of the specific type you are contemplating. Ask the seller how many of the specific type for your car they have sold or better ask the producer of the kit. Then wish yourself luck.

Your car. Your money. Your peace of mind. Your choice.

jaetee

UPDATE: over 5k miles on my EPS Eternal bearing as of now and I have been revving the car to my heart's content... Car runs like a dream. Used Oil Analysis came back perfect.

Schnell Gelb

Still only one example. For the thousands that Vertex claim to have installed, you'd think there would be more feedback. Thanks to Jaetee for helping.
Just for reference it would be interesting to add to Jaetee's post, what condition the removed IMSB was in. and single/double row

stvsxm

with all due respect, 5k miles isn't exactly a glowing testimonial. I would be interested in what the results are at 70k. an old bicycle sprocket can probably go 5000 miles...

jaetee

No argument from me there... I agree 100%. I just saw this thread pop up on the radar and was feeling talkative. I hope others with EPS cylinder bearings and more miles on the clock chime in.

For that matter, that also means anyone who has had a rebuilt Vertex engine put in their car over the last three years feel free to let us know how your IMSB is holding up (you also have an EPS bearing in your car).

5CHN3LL

Since there are several known examples of retrofit bearings failing almost immediately after installation - whether due to poor installation, a bad bearing, misalignment of the stars, or because Howard Carter doomed us all by opening Tut's tomb - I think it IS useful information that all is well at the 5K mark.

Is it enough information for me to rush out and act upon? No, of course not - but it's information, and as Schnell Gelb pointed out, there is a dearth of data...so anything helps.

Schnell Gelb

He is right!
I hope other EPS and RND or other roller bearing IMSB users will chime in with as much technical detail as possible. I would rather have such anecdotes than nothing. Nobody is claiming that a handful of experiences constitutes a valid test- come on ! So thank you to any contributors.

Device2

Adding another to the list..
I've got 500 miles on my EPS Roller Bearing with the oil feed hex mod installed. I know it's not an astonishing amount of data but it's a start and will continue to contribute as time goes on. I too snagged one up for $450 had an original 00 Dual Row IMSB (Tiptronic) 100K miles that wobbled and had evidence of wear on the sides of the bearing casing. I replaced mine while doing an engine refresh after discovering plastic parts in the oil pan (which were parts of the VarioCam Solenoid pads & a pieces left behind after the previous PO changed the spark plug tubes). During tear down I found the old Original bearing to wobble a lot, then after it's removal I saw all the metal shavings were trapped in the sealed inner section of the IMS shaft, so never got the telltale shavings in the filter. Since then car has been reassembled and running now, sounds and preforms great.