IMS again

[marsheng]

This has been discussed to death in various forums but I'm looking for a fresh look at the problem. I have a 1998 and I do question the current findings.

If the bearing was underrated, then all IMS bearings would fail at roughly the same point but they don't. The figures I have seen are 1% of the older cars and 8% of the newer ones. However some cars do +100K miles and no problem. I don't believe that that IMS bearing is underrated. It is highly loaded but within spec. It could have been designed better, however, its not the problem.

There has to be some other factor causing the failure.

Here are a few that I'm thinking of

1 Could a low oil level reduce the oil to the bearing

2 Could it be either high or low RPM be a factor, ie slow town driving or many track days

3 As time has gone on, the zinc, (high pressure lubricant) in oils has been reduced to save the catalytic converters. Maybe other suppliers of oils could have a lower zinc contents. In my vintage race bike, I went through rockers quite regularly till I swapped to a high Zinc oil. Problem gone.

4 were the cars were driven in the odd high temperature days and the weight oil was therefore below the recommended value.

5 Oil does break down over time and changes its viscosity. Were the oil change intervals extended?

6 were the cars standing for long periods of time ? Oil dripped down thus when started the bearings were dry.

Keen to hear other peoples opinions.

Some reading

https://www.timken.com/pdf/5892_Bearing%20Damage%20Analysis%20Brochure.pdf

Spent years chasing 2 stroke seizes till I read this article.

http://www.marshland.co.nz/ftp/Files/topend_rebuild6.pdf

Basically all seizes are oil failures.

Cheers Wallace

[piper6909]

Hi Wallace. You're basing all you scenarios on the oil, but the oil level, quality, viscosity, etc should have no 'bearing' (pun intended), because the bearing is sealed and has grease in it.

One thing the oil CAN do over time is become acidic and break down the seal and eventually wash away the grease.

From what I've read, lubrication is the major factor, but it has nothing to do with the oil level or viscosity, it has to do with the bearing losing its grease. Which is why some solutions use an open bearing and constantly pump oil into the bearing, whether it's from an external line or through the IMS tube itself.

[mikefocke]

Hey, we need to rehash a subject that must have been discussed hundreds of times on this forum already. And thousands of time on all the Boxster forums taken together. Then add in the 911 forums...

[maytag]

Originally Posted by mikefocke

Hey, we need to rehash a subject that must have been discussed hundreds of times on this forum already. And thousands of time on all the Boxster forums taken together. Then add in the 911 forums...

I'm with Mike on this..... I think I could probably find 5 posts online SOMEWHERE that read nearly word-for-word like the post below.

You're "keen to hear others thought"? Probably not too keen, or you'd have read then already. Your post rehashes a line of thinking that's been argued dozens of times just in the 2 years I've owned my car. Don't know what'd make your query any different?

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[Starter986]

Originally Posted by mikefocke

Hey, we need to rehash a subject that must have been discussed hundreds of times on this forum already. And thousands of time on all the Boxster forums taken together. Then add in the 911 forums...

I agree with Mike. However on another note, Mike, which tires do you recommend and which oil are you running? I can't find anything online.

[marsheng]

Sorry my mistake. I read about several suppliers with oil fed solutions and never having worked on a motor, didn't realize it was a sealed bearing. That eliminates a huge number of issues.

There are however many sealed bearings that last virtually forever. If so few fail, then it could have been a batch problem from the supplier.

This discussion however made me rethink 'hope it lasts' option to and oil fed solution.

Thanks for the input.

And now for those tires and oil, I will !!!!!!!!!!!!!!!!!!!!!!!! Ha Ha

[maytag]

Originally Posted by marsheng

Sorry my mistake. I read about several suppliers with oil fed solutions and never having worked on a motor, didn't realize it was a sealed bearing. That eliminates a huge number of issues.



There are however many sealed bearings that last virtually forever. If so few fail, then it could have been a batch problem from the supplier.



This discussion however made me rethink 'hope it lasts' option to and oil fed solution.



Thanks for the input.



And now for those tires and oil, I will !!!!!!!!!!!!!!!!!!!!!!!! Ha Ha

Yeah, the oil-fed solutions are changing the bearing to an open bearing, which requires constant lubrication. (iiuc)

For me, I wish someone would develop a replacement bearing that's more like a traditional crank bearing, with a direct oil feed to it, and bearing "shells". This makes so much more sense to me, and would have the happy benefits of still staying largely "in-place" if the bearing failed, si timing remains close, meaning no other parts in the motor get damaged. It would also be easily replaceable if damaged.

But that would be FAR too easy for the Porsche community.... Haha. I mean, it'd be almost sacrilegious to put a simple and robust bearing in a motor with 5 chains, all those ramps and hydraulic tensioners, the craziest Air/Oil separator system I've ever seen.... etc etc.

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[particlewave]

It has a 5 year warranty because it’s aluminum and does not have a replaceable sleeve.

For a $1500 part with no moving parts, and “Designed for the life of the engine”, I would expect nothing less than a lifetime warranty.

[maytag]

Originally Posted by particlewave

It has a 5 year warranty because it’s aluminum and does not have a replaceable sleeve.

For a $1500 part with no moving parts, and “Designed for the life of the engine”, I would expect nothing less than a lifetime warranty.

Shame that they aren't using a replaceable bearing shell. That'd be so much easier, too, since one could mic the parts and buy the right thickness for the parts you've got.

Shame.

And I agree: "built for ther life of your engine" should come with lifetime waranty. Otherwise, I'd change the tag line to "built to last you five years".

?? Pfft.

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[azlvr]

Originally Posted by particlewave

It has a 5 year warranty because it’s aluminum and does not have a replaceable sleeve.

For a $1500 part with no moving parts, and “Designed for the life of the engine”, I would expect nothing less than a lifetime warranty.

All warrantees are just insurance policies that are factored into the price.

[piper6909]

Originally Posted by azlvr

All warrantees are just insurance policies that are factored into the price.

True. So when they sell a part that probably costs $20 to manufacture for $1000-$1500, you'd think a lifetime warranty would already be factored in.

[Subman]

I just had the LN IMS Retrofit done on my 02 Boxster S at 115,000 miles. When it came out the original IMS bearing was, in a word, perfect; it was in like-new condition. Still happy I had it done.

I intend to do the same thing in the spring on my 00' Carrera with only 34,000 miles. There are zero signs the car needs it; oil change at purchase showed (when the old filter was cut open) zero particulate inside, and the car's been dealer serviced regularly. Nonetheless it'll get done.

It's a really simple equation.

1. There's a (low) failure rate of some number with these bearings, and there's no accurate data on what percentage will fail. There's also no accurate predictor as to which cars are going to fail (high miles vs. low miles, single row vs. double row, oil changes at X miles vs. Y miles, etc.)
2. The vast majority of IMS bearings won't fail (as evidenced by mine, which was a single row in great shape after 115K).
3. Resale value of cars with IMS bearing replacement is higher.
4. Having the bearing work done eliminates "not knowing" how your bearing looks. That in a nutshell is why I did mine and why the 911 will also get the work done. Simple peace of mind.

There's a lot of subjectivity, and there's no right or wrong answer. If someone decides not to replace their bearing based on the low failure rate, clean oil filters etc., that's a pretty good plan with a high chance of success. And if someone (like me) decides to go ahead with replacement based on the certainty a new bearing provides, well that's OK too. Do what works for you and enjoy the car.

[pilot4fn]

Thanks Subman, good points. I'l probably get the IMS bearing changed at the spring as I get the car out from the garage (currently hiding from the snow)

[piper6909]

Originally Posted by pilot4fn

Thanks Subman, good points. I'l probably get the IMS bearing changed at the spring as I get the car out from the garage (currently hiding from the snow)

Subman makes some good points, but consider the cost vs benefits. You can get a good used 2.7 motor from $1500-3000 depending on location, miles, etc. An IMS will cost you around $1500. So you're looking, at best, at a 2:1 insurance policy against, at worst, a 15% chance the IMS bearing will actually fail.

Is it worth it?

I have a 2002 with 93K miles and Tiptronic. If I had a manual and needed to change the clutch, the IMS bearing may have been a "while you're in there" sort of thing. I don't, so it's not worth it for me.

[maytag]

Originally Posted by piper6909

Subman makes some good points, but consider the cost vs benefits. You can get a good used 2.7 motor from $1500-3000 depending on location, miles, etc. An IMS will cost you around $1500. So you're looking, at best, at a 2:1 insurance policy against, at worst, a 15% chance the IMS bearing will actually fail.



Is it worth it?



I have a 2002 with 93K miles and Tiptronic. If I had a manual and needed to change the clutch, the IMS bearing may have been a "while you're in there" sort of thing. I don't, so it's not worth it for me.

FWIW, when I installed a used motor, 78k miles, into my '03 S, I elected NOT to replace the IMSB. There are so many things that can take out these motors, it seems the IMSB has a relatively low failure rate, comparatively. (When all is taken in aggregate)
Why bother?

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[mikefocke]

Of course there is always the chance that the new bearing is bad (low, perhaps, but always a chance) or the installation flawed.

There is accurate failure data from Porsche as revealed in the lawsuit. Only accurate as of the date of the lawsuit which is a long time ago and more cars have accumulated more miles since then. So are the failures higher now? One would think so as more cars are at greater mileage than was factored into the original admission by Porsche.

[BoxMann]

Originally Posted by mikefocke

There is accurate failure data from Porsche as revealed in the lawsuit. Only accurate as of the date of the lawsuit which is a long time ago and more cars have accumulated more miles since then. So are the failures higher now? One would think so as more cars are at greater mileage than was factored into the original admission by Porsche.

From everything I've read, failure rates for the Gen 2 bearing are anywhere between 5% - 20%. Pick your lucky number. IIRC, 8% was the number in the lawsuit, but that's on limited data that existed at that time, and therefore, should not be applied or relied upon universally.

[BoxMann]

The cost/benefit analysis doesn't support replacing the IMSB. Not even close.

I can walk y'all through the numbers, but you probably know them already.

That said, if I were replacing the clutch, I'd probably do it then just as a "while you're in there" item. But not otherwise.

[piper6909]

Originally Posted by maytag

...There are so many things that can take out these motors, it seems the IMSB has a relatively low failure rate, comparatively. (When all is taken in aggregate) ...

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Agreed.

Originally Posted by BoxMann

... if I were replacing the clutch, I'd probably do it then just as a "while you're in there" item. But not otherwise.

Exactly.

[pilot4fn]

Originally Posted by BoxMann

That said, if I were replacing the clutch, I'd probably do it then just as a "while you're in there" item. But not otherwise.

Even bette point, thank you. Will follow the clutch and do both as the time comes