100k IMS Bearing

[harryrcb]

HI Wayne,
Did you get a chance to evaluate the 100k IMS bearing I sent you? Just curious as to what you think. I did noticed when I sent it that the shelf I had it sitting on for about 3 weeks had oil that came out of the bearing all over it. that's why I put it in a sealed plastic bag.
Just the fact that it was full of oil is some kind of indicator that the seal was not working properly. But the fact that this car was driven hard all the time, track and street should also be an indicator.
Please let us know what you found.
Thanks
Harry

[Wayne 962]

I have it in a plastic bag in my truck, I just brought it home tonight. I will go get it now, actually.

-Wayne

[Wayne 962]

Actually, the bearing looks near perfect. Except for oil inside (which everyone seems to have), it seems very good.

What were the oil change intervals on this engine?

-Wayne

[Keithr726]

What a sign of hope to a potential 03 986s owner with 90k.

[mikefocke]

Why is a bearing designed to be lifetime lubricated by grease termed OK when, on examination, it has only oil in it?

To me this means the inner seal has failed to do its job and oil has penetrated at some unknown rate. The oil may sit in there and be heated until it fails to lubricate because it isn't circulating freely and being cooled by the normal mechanisms (anti-freeze/radiators/exchangers, etc). Or it may leak out and, on starting, when the revs are low, it may be starved for lubrication until the splash penetrates what is left of the seal. In either case wear and eventual failure should result.

What am I missing here folks?

[BerneseMtnDog]

At 84k that's exactly what mine was like. Pretty nice bearing with oil inside. Same conclusion as Mike, the beginning of the end for that bearing with who knows how many miles it'll take to get there.

Steve
2000 2.7L

[harryrcb]

Originally Posted by Wayne at Pelican Parts

Actually, the bearing looks near perfect. Except for oil inside (which everyone seems to have), it seems very good.

What were the oil change intervals on this engine?

-Wayne

I will have to check on that but I know he was diligent in doing oil changes. I will get details from him asap.

thanks for taking the time

[Wayne 962]

I spoke with someone today about the IMS issue, and I likened it to a sealed room with a big bucket of water in it. Since the room is sealed, there is no where for the water to evaporate to, so it gets old, and musty, and moldy in the room. Recirculating air in the room would fix the problem. In the same manner, the oil in the IMS area gets old and decrepit with age. With no fresh oil circulating in there, the prevailing theory is that the bearing begins to wear prematurely.

In college, we never were taught to use these sealed bearings in an oil bath environment. As I wrote in my book, these bearings are probably best used in applications like copy machines, where the seals are designed to seal against dust - not oil and gasoline (as a contaminant) mixtures. I think this is the wrong application for this type of bearing.

-Wayne

[JFP in PA]

Actually Wayne, it would seem a bit more complex. Yes, oil does intrude into the IMS bearing, but it is not the failure of the oil over time that leads to the bearing starting to gall and fail, it is caused by the oil intrusion slowly washing the grease out of the supposedly sealed bearing. Here is a photo from another website discussing oil intrusion; the bearing seems in very good condition with little apparent play, but it is obviously full of oil even though the seals seem quite intact. The owner set the bearing on clean paper and let it sit for about 24 hours, the stain is the oil that seeped out:



Grease is a much better lubricant than oil when there are factors of high temps and loadings involved, particularly when there is no way to “refresh” the lubricant; a wheel bearing is the perfect analog. Eventually, in the M96/97 the oil washes most, if not all of the grease out, leaving behind a slight amount of oil that then gets the loving Hell beat out of it; which is why people that pull the factory IMS bearing often comment about its “rancid” odor. Oil, particularly oil under high heat/high shear conditions needs periodic replacement; otherwise it shears down and no longer performs its critical functions very well. Eventually, the balls in the bearing begin to gall and chew up the races, at which point the bearing starts to wobble, in some cases totally destroying the seals, and then fails. People often ask why the process does not stop once the seals crap out, the reason is the bearing is already too far gone to have any hope of surviving at that point. The reasons that LN Engineering’s bearing lives without the grease is that it uses much harder components, and gets refreshed with clean oil constantly.

Unfortunately, the use of a sealed bearing in this application was a bad idea from the outset………….

[Wayne 962]

I hear what you're saying, and that is exactly Charles Navarro's opinion on the subject. However, he and I have discussed it at length many times, and this is indeed just an educated guess. I have some issues with the premises. First of all, this application is not high loading and not high temp. 200 degrees is not considered terribly high temperatures for a bearing like this. I researched it, and there are other bearings available that are higher temp applications, and I believe the only difference is the seal (I'd have to check).

As for the loading, it's very low for a traditional ball bearing of this design. Unlike a wheel bearing, the loading on this shaft is extremely low - it's really only applied through the tension applied by the chain tensioners. It's not like the weight of the whole car is sitting on it, like a wheel bearing.

The longest LN bearing has now gone about 30,000 miles, so we don't have any data on it as of yet. It may last forever, or it may suffer a similar fate as the stock bearings - no one knows just yet.

I'm not saying that your theory is incorrect - only that we just don't know. The big problem is explaining how some bearings only last 30,000 miles, and some last 130,000 miles. There's some other factor accelerating or retarding the wear of these bearings. I've talked with Charles for hours on this, and neither of us have any definitive answers. My personal best guess answer is that it might have something to do with the viscosity of oil used in the engine.

-Wayne

[ChrisJP]

Originally Posted by JFP in PA

people that pull the factory IMS bearing often comment about its “rancid” odor.

Is it possible to "smell" this rancid odor from the inside of the car in case of leak?
I'm asking this because last week I noticed once a really bad rancid smell in the car, together with some oil leak on the floor (not that much thought, about 1/4 cup or less).
Didn't happen again so far.

[JFP in PA]

Wayne, you raise good points. The biggest problem in assessing how these units fail is the fact that you cannot actually see it happen, which often happens in a very short time span, and (as far as I am aware) no one has developed a simulation that can repeat it outside the engine cases. So any conjectures on the actual mechanism, mine included, represent educated supposition at best.

As for temperatures, I think that once the oil has washed out the grease, the actual bearing (and oil in the bearing) temps are much higher than 200F. The circulating oil in these engines often well exceed 230F while running, and judging by how the internal components of a failed bearing looks, it got a lot hotter inside the unit before it crapped out.

As for the actual load factor on the bearing, you are correct that it is no where near that of a wheel bearing, but as soon as the engine failures became evident, even Porsche tried using replacement bearings with larger bearing ball surface contact areas (the dual row and much larger “final” version); they seem to suspect that dispersing the existing loads over a larger area matters, hence my comment.

I fully concur that oil weight comes into play. All full synthetics have both lower surface tension and higher detergency properties than conventional oils, which is one of the many reasons they are preferable lubricants. But in this situation, very low viscosity (e.g.: 0W-anything) oils may also accelerate the process of washing out the grease, creating the worst case scenario for the IMS bearing.

[JFP in PA]

Originally Posted by ChrisJP

Is it possible to "smell" this rancid odor from the inside of the car in case of leak?
I'm asking this because last week I noticed once a really bad rancid smell in the car, together with some oil leak on the floor (not that much thought, about 1/4 cup or less).
Didn't happen again so far.

Not necessarily. Even while removing a bearing that was later found to contain really foul smelling oil, you normally do not smell the odor, it only becomes evident when you pop the seals off and the oil that has been inside for a while comes out; quite often that oil really stinks. Occasionally, you will get a whiff of it when you pop the rear cover off the IMS bearing just prior to pulling it, but that is the exception more than the rule. When you drain the engine oil prior to starting an IMS upgrade, even in cars with obvious bearing issues (metallic sheen in the oil, granular ferrous metal in the filter), the oil does not emit a particularly strong smell.

[Wayne 962]

Originally Posted by JFP in PA

as soon as the engine failures became evident, even Porsche tried using replacement bearings with larger bearing ball surface contact areas (the dual row and much larger “final” version); they seem to suspect that dispersing the existing loads over a larger area matters, hence my comment.

Actually, it's mixed here. The dual-row was first, and then came the single row bearing later on. Both seem to experience the failures equally meaning that loading should not be a factor. The dual-row should be twice as strong as the single row, but in fact, with respect to this failure mode, it is not. Porsche did go with the larger bearing in the later models, but I'm not sure what their reasoning was for this, since the loading of the bearing is low, and the switch from single to double row didn't seem to affect the failure rate, for the better or for the worse.

When I was talking to NSK earlier this year, they mentioned (if I recall correctly) that the bearing seal was the cheapest you could get. You could get a better seal (for 50 cents more) that would be high-temp and "abrasive" environments, or something similar to that. I think that Porsche just went with specing out the basic seal here.

-Wayne

[mikefocke]

Will your kit include this improved bearing seal?

[Wayne 962]

Originally Posted by mikefocke

Will your kit include this improved bearing seal?

I'm going to use the upgraded seal, but probably not the "high temp" seal. The folks at NSK said that would be used for applications where the temps are much greater than the ones seen in the engine. I have to check my notes for exact details though...

-Wayne

[Wayne 962]

Oh, BTW, I brought the test car home last night after it's been in the shop for other photos - running strong with no leaks! A complete save of the engine!

-Wayne

[harryrcb]

Hey Guys, on the last oil change on my car which has approx 53k on odometer I noticed on the magnetic drain plug some fine black specs witch coverd the entire magnet. I'm thinking it could be the IMS bearing which I will promptly change anyway. Although I have no other indicators of leaks or noise. Engine still purs. I pulled the tranny out this morning ( actually dropped the engine with it - doing other mods) I will let you guys know next week how that bearing looks. I did drive it hard (de's and ax's) and changed oil between 3-5 k regularly(0-40 Mobil1). In any case I will send that one to Wayne as well for further analysis. On another note I will be changing oil to 5-40 mobil 1 as per Porsche's 2005 oil recommendation chart.

[Wayne 962]

Ehh, you're probably alright. The engine contains many moving and wearable parts, and the reason why you want to use a magnetic drain plug is to indeed trap them there instead of letting them possibly get past the filter. The IMS problem is a real threat, but it's also not terribly common either. Someone asked me how many engines had been affected, and I had to guess at about 5%, maybe more, maybe less, I don't really know. But it's not 50% - that's obvious. It's also not 30% or 20% - that would be one in five. It's a low percentage. It's just that it seems like more, because the people who get affected by it are typically quite vocal about the issue.

-Wayne

[thstone]

With more than 200,000 Boxster/Cayman's built by 2009 and something like 225,000 by now, a 5% failure rate would mean 11,000+ engine failures. That seems awfully high.

My guess is that the failure rate is more like ~2% based on about 2,000 L&N IMS replacements to date (all assumed to be out of warranty repairs) and probably an equal number of warranty engine replacements for IMS failure.

Of course, this assumes that mileage is not a key factor in failures (they will be evenly distributed in mileage) and thus, an equal number of failures occurs under and out of warranty.

Just my own back of the envelope estimates.