IMS Bearing failure mode?
 

So I plan on doing the IMS bearing swap tomorrow (at 100k mi) and have been doing a lot of reading for the last week or so. Thanks to some great advice, posts, and write ups on this forum, I def feel a lot more confident then I did even 24 hrs ago.

While researching, I've also been consumed with the IMS bearing failure root cause and the engineering of a simple and permanent fix.

IMHO, Porsche took a very simple component requirement (to center and maintain a rotating shaft), a problem that engines and motors or every type have been doing since the late 1700's with the invention of the steam engine, and managed to discover an absolutely ridiculous and failure prone solution.

With all that said, here's my question (please be gentle and understand I'm a complete noob here and just am wondering everyones thoughts, opinions, and discoveries - especially those of you that have extensive experience in root cause analysis on these engines):

Without getting wrapped around the axle with the details of each individual bearing failure, it seems they all are generally described as the seals fail in some way, allowing oil to wash out the permanent grease packing which starves the bearing of lubrication, causing it to overheat/disintegrate.

Please note that I'm referring to only true IMS bearing failures and not the other failures misdiagnosed as IMS bearing failures (tensioner failures for example).

Do you guys agree with this or am I missing it?

As I considered the root cause, I wondered about not just the seal failures but the cause of the seal failures.

Thoughts?

(By the way, this doesn't include the bearing shaft failures which seems fairly well understood and isn't really a failure of the bearing itself anyway).

In my mind, without going into a big discussion about angular momentum and moment of inertia that would probably just break down into drunken arguments about time travel paradoxes and string theory inconsistencies anyway, the bearing is actually doing a pretty simple job... spinning.

So whats going on?

One thing I have wondered is what does the IMS use to control thrust forces?

The IMS bearing? I mean, the inner race on the bearing is attached the rear of the block via the IMS bearing shaft through the cover but what's controlling the longitudinal forces of the shaft?

I'm not familiar enough with the overall layout of the m96 so I'm curious as to what it uses to control the thrust forces on the IMS?

Lots of factors lead to Factory IMSB failures. The thrust of the IMS is controlled by the ball bearing, which adds insult to injury.

The reason why factory IMS bearings fail is because a ball bearing is less than optimum for this application.

Factory bearing failure isn't what destroys the engines the most, it's the loss of valve control and primarily foreign object debris that's generated when a component comprised of no less than 11 and as much as 22 wear components fills the oil after failure. This clogs the filter, opens the bypass and sends contaminated oil to every internally lubricated component within the engine.

Hey Jake, thanks for weighing in and sharing ur wealth of experience.

When you say the ball bearing controls thrust, are you talking about the races in the IMS bearing??

Is that really the only way the thrust forces on this shaft are controlled?

BTW, this statement is absolutely true. Ball bearings should NEVER be side loaded. EVER. Its a sure recipe for bearing failure. It sounds like the IMSB is constantly being side loaded to some degree.

My 2 cents...

Contaminated oil - that is oil that has not be changed over long intervals, either in miles or time - leads to seal degradation. The first condition is seen on all mileage range cars and the latter is seen in low mileage cars. After a while, the degradation becomes large enough for oil to mix with the bearing grease, but not big enough to wash the grease out completely. The mix of oil and grease causes both to lose their lubricating properties. The resulting friction leads to abnormal bearing wear. This eventually leads to failure. If the bearings were unsealed, they would be lubricated sufficiently by oil splashed on to them.

BTW: the IMS Solution, which is a plain bearing remedy as opposed to a ball bearing one, eliminates the possibility of losing 'valve control' that Jake mentioned.

I was so paranoid after reading about IMS failure that I had mine replaced last week with LN engineering along with rms and new clutch. I just bought 2.5 a bought three weeks ago and had second thoughts about purchasing a box with 112k but the owner had all service records and had also done some auto crossing with PCA nothing too harsh. Long story short IMS was in perfect condition but replaced for peace of mind. I could not be happier with it. Drove car last Sunday throught the Tail of Dragon with no issues. What a Blast! Do yourself a favor replace the Ims and just drive!

Lugging the motor which increases side loading, contaminated oil especially with moisture which causes seal failure, pitting and bearing failure. Laying up the car for winter with contaminated oil giving it several months to degrade the bearing. Overheating the motor damaging the seals.

FWIW, my car has always been in Calif and had regular weekly use and <10k oil changes. The bearing came out while doing a clutch and was in remarkably good shape with both seals intact and no visible corrosion or slop. I do 4k oil changes now and expect the LN bearing to outlast the motor.

Got the cover off. Kind of a ********************. Haha. Haven't removed the bearing yet but it looks really good so far.

Btw, getting the cover off revealed just how much lat movement is in the IMS (and how much side loading can occur on these bearings...). Don't get me wrong, I'm not suggesting contaminated oil, moisture, etc don't wreck havoc on the IMSB and its seals but jeez, there's a ton of side loading. IMO, the only true permanent fix for this problem is an oil fed journal bearing with thrust loading capabilities.

I'm not clear in what you're saying so part of my comment may be off base

If you've taken the IMSB flange off and the bearing has a lot of play, then it's degraded and nearing failure. New bearings have little or no play whatsoever.

There is a better solution out there than the ball bearing design. It's called the IMS Solution. It is for single row bearing cars only. It sounds from another thread that you might have a dual row bearing car. Dual row cars do not have a snap ring whereas single row cars do.

PS: IIRC, 99s were dual row bearings.

Thanks for the comments... just to clarify my post, the bearing itself seems very tight and in good shape. What surprised me was the play in the shaft. Not a ton, mind u but several mm. Again, that play wasn't in the bearing but in the entire shaft assembly when I was prying the cover off. My thought was that in addition to other abuses these bearings endure, the end play in the shaft has to allow a good amount of side loading as well.

Thanks for the heads up on the IMS Solution. Interestingly enough, I threw together some ideas over the weekend to replace the IMSB with an oil fed journal bearing and emailed them to some machinist buddies. What I came up with looked similar in concept to the IMS Solution solution but I decided to go as simplistic and robust as possible while minimizing part numbers and tool time on the mills so my final CAD model did wind up uniquely different then their kit.

Oh and btw, thanks for all the support to everyone and for enduring the painfully slow process as I try to differentiate between my as and a hole in the ground. Obviously, my excessive posting demonstrates I'm wearing my learning curve on my sleeve here. Haha.

I don't know if the developers of the IMS Solution are reading these posts but nice job on the eloquent oil feed source. That's what I tapped into as well in my design. Turbo'ed tuners and I'm sure just about everyone else have been using this as a source for feed oil forever and it works great. With its close proximity in our application, it just makes so much sense.

I invented the IMS Solution, all of its development has been carried out under this roof. The oil feed component was developed years ago. Everyone things that the LN Spin On Oil Filter Adaptor is just to add a spin on filter to the system, when in fact it's original purpose was to feed the IMS Solution with just filtered oil from day #1. The difference was that for years no one knew about the IMS Solution as we worked to develop it entirely in secrecy. For a reason.

Our patent application is broad and claims more than just the journal bearing for use in the IMS.

Nice job. I gotta admit, I struggled to understand the need for the spin on adapter when I first came across them, seeing as how very few boxsters are ever put under boost. However, I immediately recognized its importance when I started thinking about a more permanent and robust IMSB solution. I just assumed the adapter was a convenient coincidence though, not realizing it was the deliberate purpose from the get go. You guys def get props for developing products that are both modular and also marketable as individual components. Again, nice job.