Yet another IMS failure theory

[ftp19601960]

In short: too much fluctuation in engine oil level.
I have no idea why Porsche's engineers decided to go with sealed bearing within engine crank case where it seats partially submerged in engine oil. My understanding is that all known bearing seals are intended to keep dust from outside and relatively thick inner grease within bearing but never thin hot oil from outside. Therefore any sealed bearing will have "lifetime" grease replaced by engine oil very soon (same strange setup with seals is used in Getrag transmission). Any oil seal is constructed in such a way that lip wear is compensated by spring retainer and lip geometry is very complex especially for seals with liquid on both sides. Even that fails easily (see RMS). I never saw a bearing with such special external oil seal. Engine oil in IMS bearing is inevitable. I speculate that oil itself is not bad thing and it does not have "accumulation of contaminates" but problem is when engine oil level is low and "sealed" bearing with engine oil within, not thick grease, starts to rotate without submerging into oil at all. Seals do not hold engine oil well and IMS bearing becomes dry and wears down quickly. Without seals that is even faster. I speculate that people with IMS failure had prolonged or "standard" oil change intervals possibly with existing oil leaks which dropped engine oil level too low. Even standard "hi"/"low" difference is much bigger than 1/3 height of IMS bearing. That's why there is no understanding why some have IMS failure while others don't: there is no history of oil level fluctuation. I would say that keeping oil level at highest point is more important than frequent oil changes.
With that, two solutions possible: (1) keep oil level high all the time with stock IMS bearing (but I'm going to start with SKF/viton seals, 445F rated) which must be in good shape from start; (2) use DOF. Anything else, like splash lubrication, removing seals, hybrid bearings , double row upgrade, thick shaft, etc is "black magic". Yes, when it starts to destroy itself you may need ceramic, thick shaft (due to torque increase) to prolong agony.

[Boiler Inspecto]

FWIW: I have a hand out from Jake Raby that talks about DOF. He states they tried it early on, and that he doesn't use it today because of "less than ideal results." Also, it may have been in the same handout or a post somewhere online, he also believes that the IMS bearing failures are due to load, not lubrication, or the lack thereof; hence why the earlier small bearings fail at a greater rate than the the later, larger bearings found in the M97 engine. Good luck.

[Scnell Gelb]

As reported elsewhere- the Cliff notes:
The latest theory on some premature/frequent IMSB failure is misalignment of the IMS relative to the c/s. Jake has developed a measuring tool to identify the problem.No, not a bad install,bad from the factory.
The misalignment may be caused by cumulative adverse tolerance in the factory machining operations.
This may explain why some engines trash IMSB repeatedly despite passing pre-qualifying inspection - even the high priced/ hybrid bearings. A roller would fare no better than a deep groove ball in such circumstances ?
Jake says he has a Solution to this bearing issue but you will have to wait for it.

[Scnell Gelb]

ftp
Agree with much of what you say but:
There are reported issues with running oil level above maximum - foaming- just search
A deep sump+horizontal baffle+DOF may help because then oil level is not so critical.
Of course the ultimate DOF is LN Engineering's Solution that you can buy from Pelican. But if you have the misalignment problem(how would you know?) wait for the 'new' Solution.

[JFP in PA]

Originally Posted by ftp19601960

. Anything else, like splash lubrication, removing seals, hybrid bearings , double row upgrade, thick shaft, etc is "black magic".

An interesting concept, but it fails to account for the 25,000+ replacement units running around like this everyday, not to mention the unknown number of non serviceable factory IMS bearings also successfully running without the rear seal.

So your "black magic" must have some powerful mojo going for it..............

[mikefocke]

The IMS without the seal is lubricated at rest by immersion and at speed by a mist in the crankcase. I used "splash" once and either Jake or Charles corrected me.

I've read of a few cars where repeated total engine swaps failed with the IMS being blamed. So it may be some external variable like the drive-train, clutch, flywheel or even driving style that can cause problems too.

Of course those Porsche factory rebuilds could also be suffering from the misalignment Jake speaks of. Imagine that they failed in original car A, were then sent to the factory, rebuilt, and installed as the replacement into car B where the misalignment took the engine down again. All Porsche probably did was clean out the block and install a new factory IMS bearing which did nothing to address the misalignment. All their tests were good. As they would be for the first thousand miles. Porsche may never have known of this issue. And by now they don't care.

[Scnell Gelb]

Mike ,
I really appreciate the effort you make to get the nuances of this issue correct even when it means that you admit a mea culpa.
I too have been corrected by the Masters on the oil mist vs. splash/oil bath issue :-).
And that may be a vital issue -is mere 'mist' (it means horse manure in German!) enough to lubricate a (rear seal removed) IMSB ? If mist is good, a flood is better ? That is why I mentioned(not recommended) DOF plus deep sump. What harm could it do?

[JFP in PA]

Originally Posted by Scnell Gelb

Mike ,
I really appreciate the effort you make to get the nuances of this issue correct even when it means that you admit a mea culpa.
I too have been corrected by the Masters on the oil mist vs. splash/oil bath issue :-).
And that may be a vital issue -is mere 'mist' (it means horse manure in German!) enough to lubricate a (rear seal removed) IMSB ? If mist is good, a flood is better ? That is why I mentioned(not recommended) DOF plus deep sump. What harm could it do?

That would depend upon where the oil feed is sourced from and how it is controlled....

[Sapientoni]

All bearings fail primarily from loading and metal fatigue. Abrasive contamination is a contributing factor in certain situations. The smaller bearings will not carry as heavy a load as the later/larger bearings, so they fail at an earlier date. Bearing companies have tested bearing with no lubrication at their rated loads and rpms and found they lasted to the predicted life expectancy.

[smshirk]

What about Jake's IMS solution? The oil line comes from near the filter and runs into the engine just above the IMS. Is that a flood to lubricate the new solution?

[JFP in PA]

Originally Posted by smshirk

What about Jake's IMS solution? The oil line comes from near the filter and runs into the engine just above the IMS. Is that a flood to lubricate the new solution?

It is not a "flood", it is a controlled flow to the solid IMS Solution bearing.

[smshirk]

I didn't understand what flood means

[mcfcinusa]

A metered flow is better so you get enough oil to lubricate and cool the bearing. Excessive oil pressure will want to thrust the shaft and that can cause problems too. The shaft need to be in its "neutral" running position so no excessive end loading happens. The thrust face area of the journal/sleeve brg. has to be calculated to provide thrust control so the thrust loading is "balanced".

Too much oil supply can also increase friction/ drag and this in turn creates heat which isn't what you don't want in brgs.

Ball brgs. need the oil level at the right height which is 1/3rd of the height of the lowest ball as it travels through the oil. This is on brg. housings that have a reservoir that the brg. sits in. Another piece of info here. Don't over grease ball or roller brgs. We had problems with a brg. overheating on eqpt. at work that ran 24 hrs a day 7 days a week for at least two years non stop and we finally figured it out. One of the plant operators was overzealous in lubricating a 7" diameter ball bearing and was greasing it every shift . This led to excessive heat on the brg. and we had to monitor it 24 hrs. a day and "stand guard" at the eqpt. Once we had opened up the drain plug and allowed it to purge itself it finally came back to its normal operating temperature. After the operator had been "educated" all was well and no more problems arose. Des.

[mikefocke]

My favorite operator overzealous story involves the mysterious and repeated loss of tens of millions of dollars worth of US bonds. Only by 24 hour observation did we learn that the operator on the night shift was throwing a switch early to set up the next run. Stop doing that and no more millions lost.