Another IMS bearing thread - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Hey guys, I've been lurking around for 12 months or so gaining lots of info on my purchase last year, a '99 model 2.5 silver Boxster. I shopped in my 4.0L V8 TVR Wedge to join the 986 brigade as I'd always fancied one, even after owning a 320bhp BMW Z3m. (which my son redesigned quite badly) Although the IMS bearing is a potential issue, it is not at the front of my thoughts all the time. But I follow all the threads related to it on hear. I do and always have done all my own maintenance, from oil changes to engine rebuilds. (because I am too tight in the wallet department :ah:.) I have a clutch waiting to go in at some point, although it isn't slipping but my RMS is leaking so it is to be taken apart sometime soon. So I will fit an IMSB of some kind while in there. So to my point, I don't recall seeing the below item mentioned on here>> Porsche IMS Intermediate Shaft Bearing Repair ETERNAL FIX (ebay no. 181254668411) As you can see, (hopefully picture uploaded) it is a roller bearing as apposed to ball bearing. Has this slipped by people or is it an unproven source? Or even worse, has it slipped by me and all you guys already know about it And just because I can, a photo

A man after my own heart with the tight in the wallet department comment. Also I just don't trust anybody but me to work on my cars - too many bad experiences in that department. From what I've seen roller bearings demand that the rotating shaft be aligned axially very, very closely. Ball bearings allow much more misalignment which appears appropriate with the IMS. I put a new IMS bearing in yesterday evening. I used a sealed Nachi greased ball bearing with a vented IMS shaft. I'll tell you I'm way out in the wilderness on this one as I made it up myself, but I'm sure enough that its right to bet my engine on it.

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Do you have any pics of the vented IMS. That was one of our routes to solve the issue, but was not further developed because it requires engine tear-down. Good luck Happy Boxstering Pedro

Yes Tony, the Vertex roller bearing replacement has been discussed here previously and the consensus seems to be that, in spite of the obviously greater surface area of roller bearings, they are ill-suited to the IMS application: roller bearings are not intended for, nor are they capable of dealing with the thrust loads that the IMS is subjected to. Brad

Yes, I believe thrust or axial load handling is the big issue with the Eternal Fix roller bearing. However, according to their website that is now updated with more information, they say that they have a patent-pending way of dealing with thrust. But they don't give any technical details. They do refer to their bearing as a "thrust" roller bearing... I don't know... I'll believe it when I see it. I'd want specific technical details as to how they overcame the poor thrust handling of a roller bearing. I really question it because bearing companies have not be able to overcome this issue for decades! So I'd like to know how an aftermarket, cheap (as in low cost and sometimes low quality) parts manufacturer like Vertex cracked the code that the big bearing makers could not. Kirk Bristol

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These videos explain my thoughts on why all IMS bearings run in oil, and not grease, and what to do about it. It's simply PV=nRT, with the pressure venting through the bearing seal. For those who don't speak perfect gas law, as the air temperature inside the shaft goes up when the car runs, air is forced from the inside of the shaft through the bearing grease seal, when the engine cools, air is forced back into the IMS through the bearing grease seal. The videos show that problem and the solution, and it could be done with the shaft in, but would take cleverly designed custom designed tooling to do it. I used the pelican parts bolt (Thanks Wayne!) but chose a Nachi 6204 NSE s - the seal material is Viton instead of Buna-n - a little better material and it is a sealed bearing. 1 986 IMS Bearing Failure Mode - YouTube 3 Eliminating 986 IMSB Differential Pressure - YouTube 7 My IMS forward plan - YouTube

James,i think your on to something and obviously Pedro agrees,but how do u make drill those holes without splitting the motor and if it is possible what about the 06 thru 08 models with there bearing installed from inside the case on assembly.Again great info and well documented

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I have not looked at the larger bearing, but from what I've seen in passing there is little problem with them in the base, thought some say their reliability can be improved by removing the grease seal and relying on splash or DOF. If I had one of them I'd be tempted to leave it alone. When replacing my IMS I searched a long time to replace it with a shaft using the 6204 bearing so it could be serviced. I'm not sure that was the best choice. As far as drilling the hole with the shaft in the engine, for the removable (6204) bearing, with the bearing removed a very small 90 degree drill bit drive with a predetermined set back would need to be built. Not impossible, but not easy either. Milwaukee makes one commercially that is close, but I think it would be custom tooling to drill from the inside of the shaft.

James P, your theory seems to be based on the pressure difference that can occur within the tube, why does the simple solution of removing the IMS bearing grease seals non't address this issue?

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So I haven't stumbled across an eternal fix then, damn and blast. This is what I shopped in to join the Pcar club. Had various ones for 12 years or so but this was the best. As said, 4.0L v8, tubular chassis and fibreglass body and only 1100kg

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The lubrication properties of oil and grease are completely different. Splash oil on an open 6204 steel bearing would be dicey at best. The same bearing with grease is fine. The trick is keeping the grease in the bearing.

Tony, I remember the cars. The Boxster is, of course, much more refined, has much better handling, creates a much better exhaust note, has a much better top, is better assembled and does not have the inevitable rattles of fiberglass on a steel chassis. Cool car though. Brad

All the above reasons is why I changed to a boxster, apart from one important one, the exhaust noise. Nothing can compare to the noise of an almost straight through exhaust connected to a thundering V8 lump. The pops and bangs on the overrun is awesome. That's the only thing I miss about the TVR. So far I have fitted a double din touchscreen cd/rad/satnav/dvd player, sports back box with sports headers ready to go on soon. New discs/pads and clear rear lights which I really like

Help!!!!! I replied to this thread but it hasn't shown. It is in my post history but other than that it has disappeared

Another day, another proposed approach. Based on theory. Untested in quantity.

True enough there isn't a track record for this as I made it up myself, but based on "theory" is debatable. Its based on engineering experience with unintentional pressure vessels and the perfect gas law.

Based on theory until several have survived for many miles and months in the real innards of our engines. Only way you could have confidence that your customers investment would be protected. If I have a 8% chance of failure with the OEM single row, am I reducing risk below that figure by installing XYZ fix? Until I can answer that question affirmatively based on data ....

I didn't realize you were involved in designing an approach to fix this. What redesign approach were you involved in, and what engineering principles and testing and verification requirements did you employ? I'd like your opinion on going forward with the understanding my only customer is me. This is just a toy that may become a DD. I went with the original bearing design because I could not find actual bearing load data to perform a meaningful L10 calc. Estimating the bearing load data makes the calculation worthless - just a guess. So I trusted the Germans on that one. For the "test and verification program" (on one car!) I put off installing a new flywheel because I'm going to replace the flywheel and bearing in about 15 - 20K and assess the viability of the grease after a year. I have an identical control bearing I will cut open at the same time to compare lubricant degradation in the installed bearing. I'll let this forum know how that turns out, but it will be awhile.

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I have sent you a pm.

I was just reading through this month's edition of Porsche panorama magazine when I came across this I think it's the roller bearing IMS 'eternal fix' mentioned here. I guess the creator must believe in it enough to move from eBay listings to porsche magazines.