Another IMS bearing thread
 

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)

http://986forum.com/forums/uploads01...1384428578.jpg

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

http://986forum.com/forums/uploads01...1384429752.jpg

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.

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... :rolleyes: 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

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

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.:confused: 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?

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
http://986forum.com/forums/uploads01...1384536562.jpg

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
http://986forum.com/forums/uploads01...1384550555.jpg

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. :cheers:

I have sent you a pm.

Another IMS bearing thread
 

I was just reading through this month's edition of Porsche panorama magazine when I came across this
http://img.tapatalk.com/d/13/11/22/5yve2e9y.jpg

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.

James I have had no involvement in designing any IMS fix, neither financial or engineering. I've just followed the subject for years on several forums and been fortunate to talk to some of the developers. I do have a product development background.

I think you meant your message to be addressed to Pedro.

If you did mean it to be to me, I'd choose the product that best reduced risk and expense to me based on the available data at the time I made my choice. Not opinions or theories or marketing from what was the latest product.

We are dealing with 12 to 8 year old drive em till they drop cars, not collectables. Wonderful cars yes but these aren't 956s. I can't see putting $25k engines in a $10k car. Or the latest new IMS kit (and there are more new approaches coming folks) when there are good enough kits which will probably last as long as the rest of the engine will and they are so much better tested to do good and avoid harm than the latest and said to be the greatest. I value 12+ of real world experiences going back 4+ years over a few recent ones. When shopping for a washing machine, I also like the reviews based on long term use more than the just bought it and it is shiny reviews.

Is valuing real world experience fair to the new guys? No. So what. They have to prove themselves. Until then why would I buy into their marketing claims? What if they turn out to not be so good for the engine after a large number have been run in the real world. Low risk and good enough versus maybe great.

It's your decision and your risk and your cash.

My mistake. I mistook you for one who was doing the re-design of the IMS to improve the reliability of that particular Achilles heal. Some do, and some comment. Is valuing the opinions of those who do over those who comment fair? No, So what. I'll stick with, value and be one of those who do. That's why I came up with and implemented a unique and logical solution to the problem with minimum modification to the engine. Will it stand the test of time? Seems like it should, but maybe not, and in the end the real value is in the "doing" which is after all what I do. I can't help it.

Jamesp, I hope your approach is successful. Heck, I hope they all are. Time will tell.

Thanks, I appreciate it. And you'r right, time will tell, after I get the *^#&#%@$!!! engine back together. I'm going to start a DIY thread on the rebuild, or maybe it will be a GMA (Give Me Advice).

Here is my latest 'Bad' idea for a bearing that lives in grease and a shot of fresh grease can be injected at oil change with a grease gun.

http://986forum.com/forums/uploads01...1385441482.jpg

It will require a special seal be fabricated to be installed on the bearing in place of the original, with a grease seal like that found on an engine crankshaft.
A grease fitting can be plumbed to a location on the bottom of the bell housing with a zerk fitting for the grease insertion.
I have ordered some bearings with the metal seals to see how they are made and installed. It looks from photos that the metal seals are pushed into the groove on the outer race and then a sharp pin-punch is used around the seal to pin it in place.

A couple of thoughts that I have on this.

No I do not think that the above pictured IMS bearing is a quality, well thought out piece of equipment. Yet, I do want to add to Brad's comment about roller bearings not being designed for thrust loads. While this is true it appears that this product has integrated plain bearing style thrust washers into the bearing races.

Do I think their design will work? Probably not because they look like low grade, 5 cent parts. But, I'd sure love to hear someone try it and so I can see the pieces when their engine goes.

On another note, I have 4 engines sitting in my garage with spun bearings or d-chunked cylinders. Not a single one has a bad ims bearing. I've pulled several ims bearings and never found a single one that exhibited any play. While yes the IMS bearing is something that goes out on some cars, I think if you drive these things hard the IMS bearing is the least of your worries.

Anyone ever seen the bearing at the front of the ims shaft go out? Of course not, its a plain bearing. All it is, is the steel ims shaft riding in the aluminum casting of the oil pump.

I think from a releability stand point Raby's IMS Solution (the one that utilizes a plain bearing that is force fed oil) is the best idea to date. It's not a coincidence that the only ball bearing in these engines is commonly a failure point. Ball bearings require less lubrication and provide less drag, but wear out faster in my experience and are more susceptible to debris. So then the only problem with the IMS solution is is it's cost. But I guess that's up to the consumer to gauge the value of their engine.

I have heard this many times and while I do not disagree at all, I think it may very well be a matter of the chains throwing much more oil around and creating much more oil mist in the area of the IMS bearing at high RPMs. At low RPMs, the oil that the chains pick up stay on the chains. So it may still come down to just lubrication.
Chain saw bar oil has ingredients in it that keep the oil on the chain, and not flying off at high RPMs. On our Porsche motors, we want the opposite.

One thing I have thought about. How many ball bearings do you see fail in transmissions, wheel bearings, motor cycle engines, the way IMS bearing fail . While they may wear to a point of needing replacement, I don't recall seeing the complete failures in these bearings that the IMS bearing seems to exhibit. When the bearings are bathed in grease or oil, complete or catastrophic failures are very rare.

But Pedro's video shows centrifugal force throwing oil AWAY from the IMSB area? Not that I agree with that, but your hypothesis states the opposite.

The M96 bearings LOVE RPM because it helps unload them, the M97 bearings hate it because the components spin too fast. M96 bearings fail on the street, M97 bearings fail on the track and seldom on the street, very seldom. Load is the evil constant.

For Jake R...and just out of shear curiosity, you have put in so much time with these engines. I have the upgrade you all developed and glad I did it. That was 1,000 miles ago. We see a lot of talk in a lot of our threads about these neat little cars never being collectible. I am curious what your thoughts are on that topic. I assume most wont replace the IMS and we will start seeing a ton of failures from this as well as other parts, but do you eventually think the early survivors might actually start to hold some value? Again..just curious. You have a ton invested in these motors and realize they are not just boxster specific motors...

Its so hard to say what will happen with the value of these cars. The IMS issues and all the other deficiencies have scarred them heavily. I'd like to think that the cars will have price increases over time, especially with fixes for the major issues easily attainable today.

I can't imagine a "vintage Boxster" and out of the 32 cars that we have on our schedule for engine reconstructions only two of them are Boxsters, the rest are 996/997 or Caymans. Thats much different than the old days when we started this, back then it was rare to see a 996 here. hell, I can't imagine a "vintage 996" either.

I am not betting on the cars holding value, so in the December issue of Panorama you'll be introduced to "Cayman X" and our DFI (post 2009) engine program thats now 4 years in the making. Its always about getting into the next big thing before the next guy :-)

Thats why we went straight to 4.2 liters from the factory 3.4!

Thanks for your insight. I didnt buy mine to collect but will keep it in as great of shape as possible...seems like the only thing to do is keep it bone stock and enjoy and move on or build a big ass motor and really enjoy it for what it is.

In the early 80's no one gave much thought to vintage 914s. They were just used cars. Time will tell.

I am not familiar with the video you mentioned, but it would be nice if the oil would sling off the chains, but stick to the bearing.
When I was experimenting with getting oil to a bearing spinning at 4 - 6K RPMs, I was getting the idea that the bearing wasn't getting any oil at all. I would drop a drop of oil into the race of the spinning bearing and it would instantly vaporize. I don't think the oil ever even got to the contact surfaces.

He's posted it in several threads. In all your research I can't believe that you haven't found it.

Can you ask a more specific question? The following will clarify why I am asking.

It seems to me that the bearing is under load so long as the engine drive chains are moving. I would think the substantive issue is just how much load does the bearing bear under different operating conditions. The hypothesis I am about to advance is pure educated guessing on my part.

My theory is that forces create load - centripetal due to rotation and vibrational. At constant RPM, the bearing experiences some degree of load, say X. As acceleration increases RPMs, I think the loading increases as the chains increase rotational speed of engine components. At higher RPMs, however, the vibrational loading component decreases because vibrational amplitudes don't have time to reach their full heights.

I am not clear on the vibration part. Is that vibration of the IM shaft, or the bearing components.

Here is some information I found that touches on rpm and lubrication-

"The engineer’s initial thoughts were that the ball-separator failure led to bearing collapse, but after analysis of said IMS bearings, it would appear that bearing wear/fatigue spalls lead to separator wear and outer race failure. Separator failure and bearing collapse causes catastrophic failure of the mounting bolt(s) and IMS/timing chain components. The first recommendation was to use a bearing without seals and secondly to use a higher viscosity oil (with greater film strength). More frequent changes will also improve lubrication quality. An oil with extreme pressure additives like Moly might also further assist in increasing bearing life. 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."

Source: PORSCHE Intermediate shaft upgrade kit for PORSCHE BOXSTER ENGINE 986 AND PORSCHE 911 996 ENGINE

I have to admit I am stuck on rolling bearings for the IM shaft. I just keep asking myself why Porsche insisted on using a rolling bearing for so long. Was it because it was the best fit for handling dynamic forces that they were not able to engineer out of their production parts.

Two thoughts...

Vibration may not be the best word. I used it to make the point that IMSB is not purely rotational. There are side forces that contribute to loading. The article you referenced hit the nail on the head - spalling is is the path to failure. The rate of spalling is inversely proportional to loading, which explains the higher OEM single row failure rates. That is, higher single row point loadings lead to increased spalling compared to dual row bearings

In some sense, the IMS Solution is the biggest roller bearing possible. It provides the largest surface area to distribute bearing load.

At high rpms, ball bearings prefer an oil vapor. Take a look at ball bearing turbos, albeit at a much higher rpm, they fog the bearings.

Reading bearing manufacturer data on lubrication shows that high rpm requires lower viscosity (thinner) lubrication, and low RPM requires higher viscosity lubrication. It was explained that that the lubrication has to "be in the way" when needed, and also be able to "get out of the way" so the bearing elements can pass. This supports longer bearing life in aggressively driven cars that have engine oil in the bearing. So to the folks out there with 200K+ on their cars, we know how you drive.:D

Or they drive at really low revs with really thick oil......:p