IMS failure with LN engineering...
#1
12-10-2011, 09:15 PM
Join Date: Oct 2008
Location: South Florida
Posts: 326
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IMS failure with LN engineering...
Has anyone ever heard of an IMS failure with the LN engineering retrofit kit? I'm about to do a pre-emptive replacement on my 05 Carrera and just wondering if there are any failures with their shaft.
I'm certain it is better than the crap stock shaft (defective design) Porsche is hiding from on all these cars. Shame on them
I'm certain it is better than the crap stock shaft (defective design) Porsche is hiding from on all these cars. Shame on them
#2
12-11-2011, 12:07 PM
I hope that the LN Engineering lasts at least as long as the engine takes to get worn out from wear and tear, in order for this not to be a weak point anymore. It does little in my case as I have a 2006 Carrera S and cannot put it in unless I do a complete tear down.
So Porsche, in its inscrutable wisdom, decided to put a bigger bearing on the 2006 and onwards models but that cannot be removed as in the motors that came before. If it resulted in a 100% guarantee of no failure, fine, but is this the case?
So Porsche, in its inscrutable wisdom, decided to put a bigger bearing on the 2006 and onwards models but that cannot be removed as in the motors that came before. If it resulted in a 100% guarantee of no failure, fine, but is this the case?
#4
12-11-2011, 03:58 PM
there was a guy with an 996 and the LN upgrade on the rennlist forum with an engine failure... so I don't know...
#5
12-11-2011, 05:43 PM
I hope that the LN Engineering lasts at least as long as the engine takes to get worn out from wear and tear, in order for this not to be a weak point anymore. It does little in my case as I have a 2006 Carrera S and cannot put it in unless I do a complete tear down.
So Porsche, in its inscrutable wisdom, decided to put a bigger bearing on the 2006 and onwards models but that cannot be removed as in the motors that came before. If it resulted in a 100% guarantee of no failure, fine, but is this the case?
So Porsche, in its inscrutable wisdom, decided to put a bigger bearing on the 2006 and onwards models but that cannot be removed as in the motors that came before. If it resulted in a 100% guarantee of no failure, fine, but is this the case?
Personally, I'd still be doing oil analyses with each change, but I do that anyway with my 2009. Whether it's an aircraft engine or a Porsche sports car engine, oil analysis is a good idea because spotting signs of wear early is much smarter than having to repair something that already failed.
I have no idea why you find the choice of new bearing to be inscrutable, so I can't address that specifically. The original bearing case developed corrosion in a small but annoying percentage of the engines where it was used. When the corrosion progressed far enough to create porosity, the engine oil would seep through the case and dilute the permanent bearing grease. After enough hours of operation in that condition the grease would be too dilute to keep the load-bearing surfaces apart. That's when bearings start to fail and the hours-to-fail thereafter depends on operating conditions, but failure is inevitable. Unless you see the problem developing in the oil analysis and take remedial action before failure occurs.
The new bearing case uses a different alloy and is of heavier construction. As I understand the descriptions, so is the LN replacement. Anecdotally, the failed bearings are associated with cars that don't operate at high power levels very often, either because they are simply not driven very often or because the owner/driver is 'gentle' with the car. Those operating conditions are notorious for allowing water condensation to build up in the oil and that in turn leads to acidic elements. Those alone cause striking corrosion in engines, and we used to take interior rust for granted, despite the oil everywhere in those older engines.
Another possibility occurs to me as well. With modern engines, alloys are everywhere. The manufacturing teams must have recurring nightmares about electrolysis developing in areas reached by coolant or rainwater, so I'm sure they have a materials compatibility committee to review alloy choices in seemingly unrelated areas of the car. In designing aircraft and spacecraft we have an Antenna Review Board that does that sort of thing for electromagnetic compatibility issues.
It has occurred to me that the water content in the oil of some examples of lightly operated engines might well reach the level of an electrolyte, a conductive medium for electrolysis. We see it in the most surprising places in boats and aircraft so it's certainly possible. Of course, a supplier used to thinking of their bearing cases as being immersed in oil on the 'out' side and grease on the inside might not routinely worry about that problem. If at all. If one or more suppliers of that bearing case chose an alloy susceptible to cathodic deterioration, we would see the symptoms described in a recent PCA article.
I haven't examined the technical details of the revision Porsche made, but making the case thicker and larger would extend the hours of operation before corrosion mattered. Probably beyond the lifetime of the engine, since surface corrosion normally provides a barrier that slows or stops the corrosion of interior parts of a piece. This is so effective with aluminum that usually no coatings at all are necessary which is why we so often see aluminum devices that are ... well, aluminum-colored.
Ferrous alloys have a different structure and it takes a much thicker coating of corrosion to prevent the interior parts corroding further. As a result, sheet metal can become porous. The change to a thicker bearing case probably was driven by the need to eliminate this possibility.But going further, with electrolysis to drive the corrosion, material is stripped from a part almost visibly. Time-lapse photos of the process are frightening. (At least if you planned to hang an airplane from that wing spar.) As a very green young engineer who hadn't taken the marine engineering courses I built a diving platform off the beach of an overseas station. Just for the fun of it, and since no official funding would have been forthcoming in our lifetimes. Vague memories from a youth around boats caused me to choose extra-heavy fasteners without really doing any research. Just on a hunch. I used quarter-inch eye-bolts and half-inch lag bolts. The platform lasted about 96 hours. We finished one week, launched and anchored it in place, and had a small squall blow up that weekend. Monday morning the platform was on the beach. Falling apart. My heavy-duty fasteners looked vaporized and their molecules were plated over the alloy components I'd re-purposed from the shipping containers of high-tech equipment. (Okay, missiles. Those were that kind of days.)
Since Porsche don't use young-green-landlubbers to design their engines, I suspect the concern for this problem may be what caused the "change of alloy" that Porsche casually mentions in describing the new bearing cases. That and the change to heavier metal in the case and a likely change of suppliers as well should certainly have cured this problem.
Gary
#6
12-11-2011, 06:44 PM
Nothing engineered by Man comes with a 100% guarantee of no failure, but the revised Porsche bearing case (and for that matter the LN replacement) would move this area of the engine into the same category as every other part.
Personally, I'd still be doing oil analyses with each change, but I do that anyway with my 2009. Whether it's an aircraft engine or a Porsche sports car engine, oil analysis is a good idea because spotting signs of wear early is much smarter than having to repair something that already failed.
I have no idea why you find the choice of new bearing to be inscrutable, so I can't address that specifically. The original bearing case developed corrosion in a small but annoying percentage of the engines where it was used. When the corrosion progressed far enough to create porosity, the engine oil would seep through the case and dilute the permanent bearing grease. After enough hours of operation in that condition the grease would be too dilute to keep the load-bearing surfaces apart. That's when bearings start to fail and the hours-to-fail thereafter depends on operating conditions, but failure is inevitable. Unless you see the problem developing in the oil analysis and take remedial action before failure occurs.
The new bearing case uses a different alloy and is of heavier construction. As I understand the descriptions, so is the LN replacement. Anecdotally, the failed bearings are associated with cars that don't operate at high power levels very often, either because they are simply not driven very often or because the owner/driver is 'gentle' with the car. Those operating conditions are notorious for allowing water condensation to build up in the oil and that in turn leads to acidic elements. Those alone cause striking corrosion in engines, and we used to take interior rust for granted, despite the oil everywhere in those older engines.
Another possibility occurs to me as well. With modern engines, alloys are everywhere. The manufacturing teams must have recurring nightmares about electrolysis developing in areas reached by coolant or rainwater, so I'm sure they have a materials compatibility committee to review alloy choices in seemingly unrelated areas of the car. In designing aircraft and spacecraft we have an Antenna Review Board that does that sort of thing for electromagnetic compatibility issues.
It has occurred to me that the water content in the oil of some examples of lightly operated engines might well reach the level of an electrolyte, a conductive medium for electrolysis. We see it in the most surprising places in boats and aircraft so it's certainly possible. Of course, a supplier used to thinking of their bearing cases as being immersed in oil on the 'out' side and grease on the inside might not routinely worry about that problem. If at all. If one or more suppliers of that bearing case chose an alloy susceptible to cathodic deterioration, we would see the symptoms described in a recent PCA article.
I haven't examined the technical details of the revision Porsche made, but making the case thicker and larger would extend the hours of operation before corrosion mattered. Probably beyond the lifetime of the engine, since surface corrosion normally provides a barrier that slows or stops the corrosion of interior parts of a piece. This is so effective with aluminum that usually no coatings at all are necessary which is why we so often see aluminum devices that are ... well, aluminum-colored. Ferrous alloys have a different structure and it takes a much thicker coating of corrosion to prevent the interior parts corroding further. As a result, sheet metal can become porous. The change to a thicker bearing case probably was driven by the need to eliminate this possibility.
But going further, with electrolysis to drive the corrosion, material is stripped from a part almost visibly. Time-lapse photos of the process are frightening. (At least if you planned to hang an airplane from that wing spar.) As a very green young engineer who hadn't taken the marine engineering courses I built a diving platform off the beach of an overseas station. Just for the fun of it, and since no official funding would have been forthcoming in our lifetimes. Vague memories from a youth around boats caused me to choose extra-heavy fasteners without really doing any research. Just on a hunch. I used quarter-inch eye-bolts and half-inch lag bolts. The platform lasted about 96 hours. We finished one week, launched and anchored it in place, and had a small squall blow up that weekend. Monday morning the platform was on the beach. Falling apart. My heavy-duty fasteners looked vaporized and their molecules were plated over the alloy components I'd re-purposed from the shipping containers of high-tech equipment. (Okay, missiles. Those were that kind of days.)
Since Porsche don't use young-green-landlubbers to design their engines, I suspect the concern for this problem may be what caused the "change of alloy" that Porsche casually mentions in describing the new bearing cases. That and the change to heavier metal in the case and a likely change of suppliers as well should certainly have cured this problem.
Gary
Personally, I'd still be doing oil analyses with each change, but I do that anyway with my 2009. Whether it's an aircraft engine or a Porsche sports car engine, oil analysis is a good idea because spotting signs of wear early is much smarter than having to repair something that already failed.
I have no idea why you find the choice of new bearing to be inscrutable, so I can't address that specifically. The original bearing case developed corrosion in a small but annoying percentage of the engines where it was used. When the corrosion progressed far enough to create porosity, the engine oil would seep through the case and dilute the permanent bearing grease. After enough hours of operation in that condition the grease would be too dilute to keep the load-bearing surfaces apart. That's when bearings start to fail and the hours-to-fail thereafter depends on operating conditions, but failure is inevitable. Unless you see the problem developing in the oil analysis and take remedial action before failure occurs.
The new bearing case uses a different alloy and is of heavier construction. As I understand the descriptions, so is the LN replacement. Anecdotally, the failed bearings are associated with cars that don't operate at high power levels very often, either because they are simply not driven very often or because the owner/driver is 'gentle' with the car. Those operating conditions are notorious for allowing water condensation to build up in the oil and that in turn leads to acidic elements. Those alone cause striking corrosion in engines, and we used to take interior rust for granted, despite the oil everywhere in those older engines.
Another possibility occurs to me as well. With modern engines, alloys are everywhere. The manufacturing teams must have recurring nightmares about electrolysis developing in areas reached by coolant or rainwater, so I'm sure they have a materials compatibility committee to review alloy choices in seemingly unrelated areas of the car. In designing aircraft and spacecraft we have an Antenna Review Board that does that sort of thing for electromagnetic compatibility issues.
It has occurred to me that the water content in the oil of some examples of lightly operated engines might well reach the level of an electrolyte, a conductive medium for electrolysis. We see it in the most surprising places in boats and aircraft so it's certainly possible. Of course, a supplier used to thinking of their bearing cases as being immersed in oil on the 'out' side and grease on the inside might not routinely worry about that problem. If at all. If one or more suppliers of that bearing case chose an alloy susceptible to cathodic deterioration, we would see the symptoms described in a recent PCA article.
I haven't examined the technical details of the revision Porsche made, but making the case thicker and larger would extend the hours of operation before corrosion mattered. Probably beyond the lifetime of the engine, since surface corrosion normally provides a barrier that slows or stops the corrosion of interior parts of a piece. This is so effective with aluminum that usually no coatings at all are necessary which is why we so often see aluminum devices that are ... well, aluminum-colored.
Ferrous alloys have a different structure and it takes a much thicker coating of corrosion to prevent the interior parts corroding further. As a result, sheet metal can become porous. The change to a thicker bearing case probably was driven by the need to eliminate this possibility.But going further, with electrolysis to drive the corrosion, material is stripped from a part almost visibly. Time-lapse photos of the process are frightening. (At least if you planned to hang an airplane from that wing spar.) As a very green young engineer who hadn't taken the marine engineering courses I built a diving platform off the beach of an overseas station. Just for the fun of it, and since no official funding would have been forthcoming in our lifetimes. Vague memories from a youth around boats caused me to choose extra-heavy fasteners without really doing any research. Just on a hunch. I used quarter-inch eye-bolts and half-inch lag bolts. The platform lasted about 96 hours. We finished one week, launched and anchored it in place, and had a small squall blow up that weekend. Monday morning the platform was on the beach. Falling apart. My heavy-duty fasteners looked vaporized and their molecules were plated over the alloy components I'd re-purposed from the shipping containers of high-tech equipment. (Okay, missiles. Those were that kind of days.)
Since Porsche don't use young-green-landlubbers to design their engines, I suspect the concern for this problem may be what caused the "change of alloy" that Porsche casually mentions in describing the new bearing cases. That and the change to heavier metal in the case and a likely change of suppliers as well should certainly have cured this problem.
Gary
Do you know of reputable shops in Southern CA that can perform this work? I am in the medical field and believe in "empiric early treatment" to avoid bigger issues down the road. Obviously, maintenance is key, but replacing a known defective part seems like a no brainer, regardless of % of failure being low. I believe this to be the case in the earlier model 997's. Most are out of warranty....most of us only have "service warranties" that only replace parts that fail. I am leaning towards cashing in my 4 year "service warranty" and paying for the IMS replacement.
#7
12-11-2011, 06:48 PM
I am in the medical field and believe in "empiric early treatment" to avoid bigger issues down the road. Obviously, maintenance is key, but replacing a known defective part seems like a no brainer, regardless of % of failure being low. I believe this to be the case in the earlier model 997's. Most are out of warranty....most of us only have "service warranties" that only replace parts that fail. I am leaning towards cashing in my 4 year "service warranty" and paying for the IMS replacement.
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#8
12-11-2011, 08:48 PM
Nothing engineered by Man comes with a 100% guarantee of no failure, but the revised Porsche bearing case (and for that matter the LN replacement) would move this area of the engine into the same category as every other part.
Personally, I'd still be doing oil analyses with each change, but I do that anyway with my 2009. Whether it's an aircraft engine or a Porsche sports car engine, oil analysis is a good idea because spotting signs of wear early is much smarter than having to repair something that already failed.
I have no idea why you find the choice of new bearing to be inscrutable, so I can't address that specifically. The original bearing case developed corrosion in a small but annoying percentage of the engines where it was used. When the corrosion progressed far enough to create porosity, the engine oil would seep through the case and dilute the permanent bearing grease. After enough hours of operation in that condition the grease would be too dilute to keep the load-bearing surfaces apart. That's when bearings start to fail and the hours-to-fail thereafter depends on operating conditions, but failure is inevitable. Unless you see the problem developing in the oil analysis and take remedial action before failure occurs.
The new bearing case uses a different alloy and is of heavier construction. As I understand the descriptions, so is the LN replacement. Anecdotally, the failed bearings are associated with cars that don't operate at high power levels very often, either because they are simply not driven very often or because the owner/driver is 'gentle' with the car. Those operating conditions are notorious for allowing water condensation to build up in the oil and that in turn leads to acidic elements. Those alone cause striking corrosion in engines, and we used to take interior rust for granted, despite the oil everywhere in those older engines.
Another possibility occurs to me as well. With modern engines, alloys are everywhere. The manufacturing teams must have recurring nightmares about electrolysis developing in areas reached by coolant or rainwater, so I'm sure they have a materials compatibility committee to review alloy choices in seemingly unrelated areas of the car. In designing aircraft and spacecraft we have an Antenna Review Board that does that sort of thing for electromagnetic compatibility issues.
It has occurred to me that the water content in the oil of some examples of lightly operated engines might well reach the level of an electrolyte, a conductive medium for electrolysis. We see it in the most surprising places in boats and aircraft so it's certainly possible. Of course, a supplier used to thinking of their bearing cases as being immersed in oil on the 'out' side and grease on the inside might not routinely worry about that problem. If at all. If one or more suppliers of that bearing case chose an alloy susceptible to cathodic deterioration, we would see the symptoms described in a recent PCA article.
I haven't examined the technical details of the revision Porsche made, but making the case thicker and larger would extend the hours of operation before corrosion mattered. Probably beyond the lifetime of the engine, since surface corrosion normally provides a barrier that slows or stops the corrosion of interior parts of a piece. This is so effective with aluminum that usually no coatings at all are necessary which is why we so often see aluminum devices that are ... well, aluminum-colored. Ferrous alloys have a different structure and it takes a much thicker coating of corrosion to prevent the interior parts corroding further. As a result, sheet metal can become porous. The change to a thicker bearing case probably was driven by the need to eliminate this possibility.
But going further, with electrolysis to drive the corrosion, material is stripped from a part almost visibly. Time-lapse photos of the process are frightening. (At least if you planned to hang an airplane from that wing spar.) As a very green young engineer who hadn't taken the marine engineering courses I built a diving platform off the beach of an overseas station. Just for the fun of it, and since no official funding would have been forthcoming in our lifetimes. Vague memories from a youth around boats caused me to choose extra-heavy fasteners without really doing any research. Just on a hunch. I used quarter-inch eye-bolts and half-inch lag bolts. The platform lasted about 96 hours. We finished one week, launched and anchored it in place, and had a small squall blow up that weekend. Monday morning the platform was on the beach. Falling apart. My heavy-duty fasteners looked vaporized and their molecules were plated over the alloy components I'd re-purposed from the shipping containers of high-tech equipment. (Okay, missiles. Those were that kind of days.)
Since Porsche don't use young-green-landlubbers to design their engines, I suspect the concern for this problem may be what caused the "change of alloy" that Porsche casually mentions in describing the new bearing cases. That and the change to heavier metal in the case and a likely change of suppliers as well should certainly have cured this problem.
Gary
Personally, I'd still be doing oil analyses with each change, but I do that anyway with my 2009. Whether it's an aircraft engine or a Porsche sports car engine, oil analysis is a good idea because spotting signs of wear early is much smarter than having to repair something that already failed.
I have no idea why you find the choice of new bearing to be inscrutable, so I can't address that specifically. The original bearing case developed corrosion in a small but annoying percentage of the engines where it was used. When the corrosion progressed far enough to create porosity, the engine oil would seep through the case and dilute the permanent bearing grease. After enough hours of operation in that condition the grease would be too dilute to keep the load-bearing surfaces apart. That's when bearings start to fail and the hours-to-fail thereafter depends on operating conditions, but failure is inevitable. Unless you see the problem developing in the oil analysis and take remedial action before failure occurs.
The new bearing case uses a different alloy and is of heavier construction. As I understand the descriptions, so is the LN replacement. Anecdotally, the failed bearings are associated with cars that don't operate at high power levels very often, either because they are simply not driven very often or because the owner/driver is 'gentle' with the car. Those operating conditions are notorious for allowing water condensation to build up in the oil and that in turn leads to acidic elements. Those alone cause striking corrosion in engines, and we used to take interior rust for granted, despite the oil everywhere in those older engines.
Another possibility occurs to me as well. With modern engines, alloys are everywhere. The manufacturing teams must have recurring nightmares about electrolysis developing in areas reached by coolant or rainwater, so I'm sure they have a materials compatibility committee to review alloy choices in seemingly unrelated areas of the car. In designing aircraft and spacecraft we have an Antenna Review Board that does that sort of thing for electromagnetic compatibility issues.
It has occurred to me that the water content in the oil of some examples of lightly operated engines might well reach the level of an electrolyte, a conductive medium for electrolysis. We see it in the most surprising places in boats and aircraft so it's certainly possible. Of course, a supplier used to thinking of their bearing cases as being immersed in oil on the 'out' side and grease on the inside might not routinely worry about that problem. If at all. If one or more suppliers of that bearing case chose an alloy susceptible to cathodic deterioration, we would see the symptoms described in a recent PCA article.
I haven't examined the technical details of the revision Porsche made, but making the case thicker and larger would extend the hours of operation before corrosion mattered. Probably beyond the lifetime of the engine, since surface corrosion normally provides a barrier that slows or stops the corrosion of interior parts of a piece. This is so effective with aluminum that usually no coatings at all are necessary which is why we so often see aluminum devices that are ... well, aluminum-colored.
Ferrous alloys have a different structure and it takes a much thicker coating of corrosion to prevent the interior parts corroding further. As a result, sheet metal can become porous. The change to a thicker bearing case probably was driven by the need to eliminate this possibility.But going further, with electrolysis to drive the corrosion, material is stripped from a part almost visibly. Time-lapse photos of the process are frightening. (At least if you planned to hang an airplane from that wing spar.) As a very green young engineer who hadn't taken the marine engineering courses I built a diving platform off the beach of an overseas station. Just for the fun of it, and since no official funding would have been forthcoming in our lifetimes. Vague memories from a youth around boats caused me to choose extra-heavy fasteners without really doing any research. Just on a hunch. I used quarter-inch eye-bolts and half-inch lag bolts. The platform lasted about 96 hours. We finished one week, launched and anchored it in place, and had a small squall blow up that weekend. Monday morning the platform was on the beach. Falling apart. My heavy-duty fasteners looked vaporized and their molecules were plated over the alloy components I'd re-purposed from the shipping containers of high-tech equipment. (Okay, missiles. Those were that kind of days.)
Since Porsche don't use young-green-landlubbers to design their engines, I suspect the concern for this problem may be what caused the "change of alloy" that Porsche casually mentions in describing the new bearing cases. That and the change to heavier metal in the case and a likely change of suppliers as well should certainly have cured this problem.
Gary
I had not heard of the bearing case actually receiving any kind of change from 996 to 997 and then onwards into post 2006 built M96 derived motors.
My understanding is that the early M96 bearing design was a small single row unit that had what can be considered a high failure rate. This was mostly seen in very early 2.5L Boxsters.
Most 996s and 2005 997s have a dual row bearing that had significantly higher reliability but there were still many incidents of failure.
2006+ M96 derived motors have a much larger single row bearing that as far as I know, has extremely high longevity.
LNs research showed that the catalyst for a lot of the failures was in fact the oil used and the frequency in which it is replaced. Porsche's move to 15K+ mile oil change intervals combined with sub-standard oil. Thin old oil naturally failed to provide the necessary lubrication for the bearings. The bearings broke down causing a wobble in the IMS and a subsequent engine failure once the shaft failed.
Long story short, as you stated, monitoring your oil quality and doing more frequent changes can be as good for your engine as replacing the part all together.
Jason
#9
12-12-2011, 01:05 AM
Gary,
Do you know of reputable shops in Southern CA that can perform this work? I am in the medical field and believe in "empiric early treatment" to avoid bigger issues down the road. Obviously, maintenance is key, but replacing a known defective part seems like a no brainer, regardless of % of failure being low. I believe this to be the case in the earlier model 997's. Most are out of warranty....most of us only have "service warranties" that only replace parts that fail. I am leaning towards cashing in my 4 year "service warranty" and paying for the IMS replacement.
Do you know of reputable shops in Southern CA that can perform this work? I am in the medical field and believe in "empiric early treatment" to avoid bigger issues down the road. Obviously, maintenance is key, but replacing a known defective part seems like a no brainer, regardless of % of failure being low. I believe this to be the case in the earlier model 997's. Most are out of warranty....most of us only have "service warranties" that only replace parts that fail. I am leaning towards cashing in my 4 year "service warranty" and paying for the IMS replacement.
You should ask a dealer about your car's VIN number though. Most of the 2006 models have the improved bearing case I believe. The problem was never the intermediate shaft itself. We use those routinely in all sorts of devices. I know it's become the bogey-man because that is the part that stops turning when the bearing case lets in too much oil and the bearings finally fail. And if that shaft stops, the valves do expensive things, but the problem isn't really with the bearings even: just the casing that is supposed to contain permanent grease for those bearings. If it leaks, the grease gets diluted and the engine oil isn't thick enough to keep the load-bearing parts separated during high load operations. No problem with the bearing case, no problem with the bearings. No problem with the bearings, no problem with the intermediate shaft.
I haven't paid a lot of attention to exact dates of changeover because it doesn't apply to our dot two, but I seem to remember the original problematic bearing case was changed on the production line sometime early in 2005. You do need to have a dealer check your VIN number to be sure though. Usually, the whole production for a particular year is completed before the year begins so your car's production date is probably some time in 2005.
This work is worth doing if no one has done it already. I believe PCNA was doing them pretty regularly back when they discovered the problem, and most of the affected production units should have been changed over, but you can't be sure, so definitely ask a dealer. And if he says you do have the original bearing case, then I'd also ask PCNA to install the revised one. So long out of warranty means you might have to negotiate something less than full coverage, but one guy over on Rennlist just got the work done by PCNA at 75k miles. As I understand it, this re-work bearing case is thicker and a different alloy, but still not the same as the even better one they began installing on production line.
Swapping out the bearings with that improved case from later production is not so easy as the originals. Because they are larger, they don't fit through the available opening in the block. They have to split the block to do the replacement I believe. (Something like what they want to do to my cervical vertebrae, but I'm holding out until they have to open me up anyway to do the brain transplant at age 110.
)Seriously, if you have the newer bearing case already, this shouldn't be an issue for you, even it's just the re-work version. If you're concerned, routine oil analyses would identify a problem before it became an issue. For complete peace of mind, someone has developed a real-time oil analysis tool, so to speak. It doesn't really do an oil analysis, but it does detect the presence of metal in the oil flowing past a checkpoint. At that point, it gives you an alarm so you can shut down. The recent article in Excellence Magazine gives the phone number for the supplier and the same shop could be trusted to install such a widget.
Gary
#10
12-12-2011, 03:10 AM
Just to clarify a few things. 05 997 chassis cars all use the single row bearing. I have proactively installed the bearing in my car with the LN kit. 06 and later cars simply have a larger bearing installed which can not be extracted through the case like the 05 and earlier cars can. The casing is not thicker for corrosion resistance, the whole bearing is larger to try to better handle the loading. Corrosion is a factor with cars left alone for a long time, but it is not a primary culprit in this design issue.
Bearing Lubrication:
Proper lubrication in a rolling element bearing occurs under EHL conditions. Oil has the unique property (that water, for example, lacks) in that its viscosity increases with pressure. In a rolling element bearing, in the load zone, the lubricant instantaneously thickens to almost the consistency of solid plastic to keep the two metal surfaces separated. To ensure EHL conditions are possible, you need proper viscosity of the oil (what you might think of as the "thickness," of the oil, though the definition is simply "resistance to flow"). This viscosity of the oil is affected by the bearing's operating temperature, load and speed (i.e. RPM). Note that the faster the bearing is spinning (driving at higher RPM), the thicker the film, and the easier it is to avoid any metal to metal contact.
http://www.stle.org/UserFiles/File/c...Wear%20pt7.pdf
http://www.machinerylubrication.com/...cant-selection
Grease:
A lot of people assume that any grease is going to be "thicker" than oil (i.e. it should be able to protect and maintain EHL conditions easier than with oil). Why wouldn't you? you can turn a cup of grease upside down and nothing comes out, while a cup of oil pours out freely. In fact, this is the thickener at work. Grease is made up of base oil, thickener and additives. The thickener does not lubricate, it simply acts as a sponge. It is constantly releasing and reabsorbing oil. Its purpose is simply to make the lubricating oil stay put, in the bearing, where it is needed. Because of this, it doesn't matter how "thick" the grease appears to be, it is the viscosity of the base oil IN the grease that matters. The viscosity of the base oil in most general purpose greases is between a 40W and 50W engine oil (as in the 0W40 that porsche puts in the car from the factory...) thus the engine oil alone can likely lubricate the bearing, so long as the bearing is getting enough of it (more on that later...)
Ok, so taking that into account, lets discuss...
IMS Failure:
The issue is not porosity of the bearing case, but oil leaking past the seal. A bearing with the proper amount of grease will constantly release and reabsorb the lubricating oil from the thickener as needed. However, over time, the dilution of the grease by engine oil coming past the seal can leave the bearing essentially empty (grease is slowly washed out). Because only a bit of engine oil comes in past the seals at a time, there is also not enough engine oil supply flowing through to lubricate the bearing.
LN's solution is to use a bearing without seals (forget about grease entirely), so it gets a constant supply of engine oil (rather than being lubricated by the grease until it is washed out, and then not having enough engine oil flow to keep it lubricated). This better improves chances of EHL lubrication at any given time.
They also recommend running your car at higher RPM (remember above, high RPM = easier to reach EHL conditions.... sort of like a boat coming up on plane....).
They also use a bearing that is tougher than the factory one, so it is more tolerant of boundary lubrication (slow speed, start up conditions, unable to reach EHL conditions).
Finally, they recommend running a higher viscosity oil (as noted above, also helps with achieving EHL).
A lot of people have achieved three of the four above items simply by having their tech pull the seal off of the stock bearing. I chose to replace the thing (while you are in there, why not). But I can see either one as being a good option. Even more people do nothing and have no issues
How to (IMHO) improve your IMS life expectancy:
1. Decide if a retrofit is right for you. vast majority of people do nothing and have no issues. I decided to try it.
2. I would NOT recommend running any gimmicky off brand oil or weird viscosity. Stick to Porsche approved. I run Mobil 1 5W50, which can be found at any local Mobil distributor
http://www.distributorlocator.exxonm...tor/index.aspx
Mobil 1 0W40, Castrol 5W40, are also approved.
3. Don't drive your car hard until it is warmed up
4. Once it is warmed up don't be afraid to let it stretch its legs. Keep RPMs in general above 2000 when moving and under load (lugging your engine much below that can do serious damage beyond improper lubrication for your IMS bearing)
5. Do oil analysis if you can. PM me if you have questions as to what your results mean
6. Make sure your car is driven at full operating temp on every drive (get oil temp up to 210 degrees or higher to ensure any water condensation is boiled off from when the car was sitting). daily 5 minute trips are bad for your car if it doesn't get a longer trip at least every week or so. As noted above, water is a poor lubricant when it comes to EHL. Some condensation is inevitable so just drive your car up to operating temp and you wont have issues.
7. Cars stored for long periods of time tend to have more issues... Drive it, even in the (gasp) rain
8. Don't over worry yourself about it. Enjoy the car...
Bearing Lubrication:
Proper lubrication in a rolling element bearing occurs under EHL conditions. Oil has the unique property (that water, for example, lacks) in that its viscosity increases with pressure. In a rolling element bearing, in the load zone, the lubricant instantaneously thickens to almost the consistency of solid plastic to keep the two metal surfaces separated. To ensure EHL conditions are possible, you need proper viscosity of the oil (what you might think of as the "thickness," of the oil, though the definition is simply "resistance to flow"). This viscosity of the oil is affected by the bearing's operating temperature, load and speed (i.e. RPM). Note that the faster the bearing is spinning (driving at higher RPM), the thicker the film, and the easier it is to avoid any metal to metal contact.
http://www.stle.org/UserFiles/File/c...Wear%20pt7.pdf
http://www.machinerylubrication.com/...cant-selection
Grease:
A lot of people assume that any grease is going to be "thicker" than oil (i.e. it should be able to protect and maintain EHL conditions easier than with oil). Why wouldn't you? you can turn a cup of grease upside down and nothing comes out, while a cup of oil pours out freely. In fact, this is the thickener at work. Grease is made up of base oil, thickener and additives. The thickener does not lubricate, it simply acts as a sponge. It is constantly releasing and reabsorbing oil. Its purpose is simply to make the lubricating oil stay put, in the bearing, where it is needed. Because of this, it doesn't matter how "thick" the grease appears to be, it is the viscosity of the base oil IN the grease that matters. The viscosity of the base oil in most general purpose greases is between a 40W and 50W engine oil (as in the 0W40 that porsche puts in the car from the factory...) thus the engine oil alone can likely lubricate the bearing, so long as the bearing is getting enough of it (more on that later...)
Ok, so taking that into account, lets discuss...
IMS Failure:
The issue is not porosity of the bearing case, but oil leaking past the seal. A bearing with the proper amount of grease will constantly release and reabsorb the lubricating oil from the thickener as needed. However, over time, the dilution of the grease by engine oil coming past the seal can leave the bearing essentially empty (grease is slowly washed out). Because only a bit of engine oil comes in past the seals at a time, there is also not enough engine oil supply flowing through to lubricate the bearing.
LN's solution is to use a bearing without seals (forget about grease entirely), so it gets a constant supply of engine oil (rather than being lubricated by the grease until it is washed out, and then not having enough engine oil flow to keep it lubricated). This better improves chances of EHL lubrication at any given time.
They also recommend running your car at higher RPM (remember above, high RPM = easier to reach EHL conditions.... sort of like a boat coming up on plane....).
They also use a bearing that is tougher than the factory one, so it is more tolerant of boundary lubrication (slow speed, start up conditions, unable to reach EHL conditions).
Finally, they recommend running a higher viscosity oil (as noted above, also helps with achieving EHL).
A lot of people have achieved three of the four above items simply by having their tech pull the seal off of the stock bearing. I chose to replace the thing (while you are in there, why not). But I can see either one as being a good option. Even more people do nothing and have no issues
How to (IMHO) improve your IMS life expectancy:
1. Decide if a retrofit is right for you. vast majority of people do nothing and have no issues. I decided to try it.
2. I would NOT recommend running any gimmicky off brand oil or weird viscosity. Stick to Porsche approved. I run Mobil 1 5W50, which can be found at any local Mobil distributor
http://www.distributorlocator.exxonm...tor/index.aspx
Mobil 1 0W40, Castrol 5W40, are also approved.
3. Don't drive your car hard until it is warmed up
4. Once it is warmed up don't be afraid to let it stretch its legs. Keep RPMs in general above 2000 when moving and under load (lugging your engine much below that can do serious damage beyond improper lubrication for your IMS bearing)
5. Do oil analysis if you can. PM me if you have questions as to what your results mean
6. Make sure your car is driven at full operating temp on every drive (get oil temp up to 210 degrees or higher to ensure any water condensation is boiled off from when the car was sitting). daily 5 minute trips are bad for your car if it doesn't get a longer trip at least every week or so. As noted above, water is a poor lubricant when it comes to EHL. Some condensation is inevitable so just drive your car up to operating temp and you wont have issues.
7. Cars stored for long periods of time tend to have more issues... Drive it, even in the (gasp) rain
8. Don't over worry yourself about it. Enjoy the car...
Last edited by bergx7; 12-12-2011 at 03:18 AM.
#11
12-12-2011, 03:17 AM
Gary,
I had not heard of the bearing case actually receiving any kind of change from 996 to 997 and then onwards into post 2006 built M96 derived motors.
My understanding is that the early M96 bearing design was a small single row unit that had what can be considered a high failure rate. This was mostly seen in very early 2.5L Boxsters.
Most 996s and 2005 997s have a dual row bearing that had significantly higher reliability but there were still many incidents of failure.
2006+ M96 derived motors have a much larger single row bearing that as far as I know, has extremely high longevity.
LNs research showed that the catalyst for a lot of the failures was in fact the oil used and the frequency in which it is replaced. Porsche's move to 15K+ mile oil change intervals combined with sub-standard oil. Thin old oil naturally failed to provide the necessary lubrication for the bearings. The bearings broke down causing a wobble in the IMS and a subsequent engine failure once the shaft failed.
Long story short, as you stated, monitoring your oil quality and doing more frequent changes can be as good for your engine as replacing the part all together.
Jason
I had not heard of the bearing case actually receiving any kind of change from 996 to 997 and then onwards into post 2006 built M96 derived motors.
My understanding is that the early M96 bearing design was a small single row unit that had what can be considered a high failure rate. This was mostly seen in very early 2.5L Boxsters.
Most 996s and 2005 997s have a dual row bearing that had significantly higher reliability but there were still many incidents of failure.
2006+ M96 derived motors have a much larger single row bearing that as far as I know, has extremely high longevity.
LNs research showed that the catalyst for a lot of the failures was in fact the oil used and the frequency in which it is replaced. Porsche's move to 15K+ mile oil change intervals combined with sub-standard oil. Thin old oil naturally failed to provide the necessary lubrication for the bearings. The bearings broke down causing a wobble in the IMS and a subsequent engine failure once the shaft failed.
Long story short, as you stated, monitoring your oil quality and doing more frequent changes can be as good for your engine as replacing the part all together.
Jason
) Porsche had the M96/01 engine which I believe mechanics refer to as "the five-chain engine." Then, in 2002 I believe, the M96/03 was introduced and had only three chains! (Oh, just shoot me now. Please.) The M96/05 came out in 2005 for the base Carrera at the same time the M97/01 was introduced with 3.8 liters for the S model. Even some of the most basic configuration elements change within those first two digits of the model designation. (Even the chain count, for all love. Where is Mr. T when we need him?) The parts commonality between any two designs is often less than 50%, and one of the biggest reasons for design changes is regulatory changes in emissions and such. The variable cam operations are an important part of the designers' dealing with those rule changes. When they change the way the valve timing is controlled, they change everything upstream clear back to the crankshaft. That includes the IMS bearings potentially, so we may be looking at five or six different types by now. And we're not even discussing the Boxster variations or the changes when the 997 was introduced.
It's true the M97/01 is derived from the same engine design as the M96 generation, but that's a little like the equally true observation that the M64 engine in the earlier cars was derived from the first flat six in the 901. It was, but there's a lot of development work between any two engines in a family defined that broadly. Just as an example, the increased displacement of the M97/01 required a vibration damper on the crankshaft and the increased blow-by required a new design of air/oil separator. Okay, sounds easy enough to spot. Still basically an M96, right? No. The M97/01 has less than 30% of it's parts in common with an M96/05, let alone the earlier members of that design family.
I honestly think the LN Engineering mod is a good piece of work, but I also think their explanation has been run through one too many marketing people before it reached us. The engine oil is always important, and these type of bearings have separator gaskets, grease seals that is, as well as a bearing case and ball separators, so oil deterioration could hasten the aging of those gaskets I suppose. Callas and Prine mention their concern for that sort of deterioration in their articles. Whether I share their concern for it causing IMS failure is moot because the recommendation is good for other reasons: change the oil regularly; more quickly than the factory recommendation which is probably influenced by Green pressure; and definitely let your engine warm up fully on each run. Babying an engine constantly just leads to the acid build-up that is bad for all parts of the engine, not just these bearings. My thought about cathodic deterioration from electrolysis is only that: a late-night thought tickled by the anecdotal link to lightly-driven engines. I have no evidence for it, but it's the way an engineer's mind goes when looking for diagnosis of something like this and I wouldn't be at all surprised if it's one of the possibilities Zuffenhausen evaluated.
With that said, I'm afraid I can't buy the details of that other explanation. The IMS bearings are not lubricated by oil. They use a permanent grease. Whether the sealing gaskets are deteriorating or the metal case itself, the loss of that grease is the root cause of the later bearing failure. If you're down to the oil being the only protection for those bearings they're about to fail anyway, no matter what oil you use.
I haven't heard of an intermediate shaft itself failing, though anything is possible once a set of roller bearings die. The early symptoms of bearing distress are what we look for in oil analysis. That widget I spoke looks for something I'd characterize as being slightly later in their deterioration: actual metal chips in the oil. Or so they say. They use detectors derived from the ones we use in aerospace, and they certainly work if the implementation is correct. See the Nov 2011 Excellence and their website for the IMS Guardian. Their explanation of the failure mechanism is even worse than the one we're discussing, but as long as you get the sensor their reasoning doesn't matter.
LN engineering is marketing the product as well. For some reason, they describe it as being for Carreras to 2004 only. Perhaps they overlook the M96/05 in the early 997's or possibly detail design issues like the mounting location may have changed enough that the model currently being sold won't install properly on a 997. A phone call is in order I think.
Gary
#12
12-12-2011, 08:23 AM
Does anyone know what type of plastic is used to seal the OEM bearing? I am curious as the standard crankcase fill is Mobil 1 which is a polyalphaolefin. Some synthetic lubes are actually gas to liquid conversions ( natural gas to long chain molecules) so they can say " synthetic". Some synthetics are based on polyol esters. These are typically used in jet aircraft but can have a swelling effect on some plastics and elastomers. I am simply wondering if there is a correlation between the use of "high performance " synthetics and failure of the internal IMS bearing seal.
#13
12-12-2011, 10:37 AM
Does anyone know what type of plastic is used to seal the OEM bearing? I am curious as the standard crankcase fill is Mobil 1 which is a polyalphaolefin. Some synthetic lubes are actually gas to liquid conversions ( natural gas to long chain molecules) so they can say " synthetic". Some synthetics are based on polyol esters. These are typically used in jet aircraft but can have a swelling effect on some plastics and elastomers. I am simply wondering if there is a correlation between the use of "high performance " synthetics and failure of the internal IMS bearing seal.
In terms of your oil question, any API certified oil (e.g. SM or the newest SN) is going to be fine in terms of seal peformance. Gas to liquid technology is not yet on the market so I won't address that yet. Most synthetic lubricants contain a blend of basestocks for maximum performance. You could have a product with PAO, and esters, and more. Simply targeting a single basestock is silly, though some companies love to claim that as a benefit. The bigger "issue" seems to be companies marketing what would typically be considered mineral oils as synthetics (able to do this due to lack of regulation around the term, except in Germany, where "synthetics" have to be primarily PAO based). Again, stick to Porsche approved products.... pretty simple...
SIMSGW, to address your point:
"With that said, I'm afraid I can't buy the details of that other explanation. The IMS bearings are not lubricated by oil. They use a permanent grease. Whether the sealing gaskets are deteriorating or the metal case itself, the loss of that grease is the root cause of the later bearing failure. If you're down to the oil being the only protection for those bearings they're about to fail anyway, no matter what oil you use."
You probably wrote this before seeing my post but this is incorrect. Oil lubrication is actually better for bearings in terms of heat dissipation, contamination removal, etc. Grease is always a compromise from a lubrication standpoint (that being said, it isn't feasible to put a circulating system on every bearing or bushing out there, so grease makes it work). The important factor is the underlying viscosity of the oil IN the grease (all grease does is hold the oil in the right place. Nothing is "lubricated" by grease, it is lubricated by the oil, which happens to be suspended in a non-lubricating thickener, the mix of which is something we happen to call grease).
I do fully agree with you that LN Engineering's explanation is somewhat skewed by a lack of knowledge of lubricant chemistry and the importance (or lack thereof) of certain additives. They are also selling a small private label lubricant product on their site, go figure
You will note in my tips for IMS life that I don't mention changing the oil too often. If you are doing oil analysis, it will tell you when to change. 99.9% of enthusiasts (100% of racing teams...lol) change the oil far before it is due. 20k mile drains are fully possible on this car if you go by the analysis. There are over the road heavy haul diesel truck customers running 100,000 mile intervals. That being said, I change Porsche's oil around 7500 miles, purely because the car doesn't get that many miles each year and I like to get under it and take a look around at least once a year 
If you aren't doing oil analysis, and you want to be super **** to minimize any miniscule potential for lubricant related issues, change the oil once per year or every 10,000 miles (whichever comes first).For what it is worth, I run 0W20 in my toyota 4Runner at 12,000 mile intervals. It still looks great on the analysis when I change it.
#14
12-12-2011, 03:14 PM
[...]
SIMSGW, to address your point:
"With that said, I'm afraid I can't buy the details of that other explanation. The IMS bearings are not lubricated by oil. They use a permanent grease. Whether the sealing gaskets are deteriorating or the metal case itself, the loss of that grease is the root cause of the later bearing failure. If you're down to the oil being the only protection for those bearings they're about to fail anyway, no matter what oil you use."
You probably wrote this before seeing my post but this is incorrect. Oil lubrication is actually better for bearings in terms of heat dissipation, contamination removal, etc. Grease is always a compromise from a lubrication standpoint (that being said, it isn't feasible to put a circulating system on every bearing or bushing out there, so grease makes it work). The important factor is the underlying viscosity of the oil IN the grease (all grease does is hold the oil in the right place. Nothing is "lubricated" by grease, it is lubricated by the oil, which happens to be suspended in a non-lubricating thickener, the mix of which is something we happen to call grease).
SIMSGW, to address your point:
"With that said, I'm afraid I can't buy the details of that other explanation. The IMS bearings are not lubricated by oil. They use a permanent grease. Whether the sealing gaskets are deteriorating or the metal case itself, the loss of that grease is the root cause of the later bearing failure. If you're down to the oil being the only protection for those bearings they're about to fail anyway, no matter what oil you use."
You probably wrote this before seeing my post but this is incorrect. Oil lubrication is actually better for bearings in terms of heat dissipation, contamination removal, etc. Grease is always a compromise from a lubrication standpoint (that being said, it isn't feasible to put a circulating system on every bearing or bushing out there, so grease makes it work). The important factor is the underlying viscosity of the oil IN the grease (all grease does is hold the oil in the right place. Nothing is "lubricated" by grease, it is lubricated by the oil, which happens to be suspended in a non-lubricating thickener, the mix of which is something we happen to call grease).
Honestly, I'm best at electron movement and all the variations and derivatives of that phenomenon, as I'm often reminded by my nephew. (Little whippersnapper ended up at Scripps doing stuff I don't pretend to keep up with, but I suspect you two could have a lovely conversation about molecular design.) In any case, petroleum engineering is definitely not my field, so I'll accept your information without quibble.
I'm curious whether the soap thickener doesn't have some effect on the lubricating properties of the oil component. I don't offer a demurrer you understand, just curiosity. And personally, I could accept the oil providing equally effective lubrication of a bearing when it's present in the required quantity to stay in the correct operating temperature range. But I'd worry that a bearing in the axle style in a location intended for grease-lubrication would have that supply of oil. Granted, it is located where the oil supply is potentially available, but I'd worry about drain down when I don't drive for several days. Am I being obsessive here?
[...]I do fully agree with you that LN Engineering's explanation is somewhat skewed by a lack of knowledge of lubricant chemistry and the importance (or lack thereof) of certain additives. They are also selling a small private label lubricant product on their site, go figure
I'm beginning to notice an interesting aspect of this problem. If we were a Tiger Team allocated to find an answer, or at least pin down a chain of causation, I'd start to assign sub-teams about now. We have plausible candidates in mechanical, electrical, and chemical directions.
The mechanical attempt to explain points the finger at the broad spectrum goal of reducing manufacturing cost with the 996, and specifically the choice of a single-row bearing rather than the double-row that came later. The electrical (in the sense of electron movement, not the wiring harness) sees a potential for electrolysis when so many new alloys were introduced in the design. And of course, the chemical points to degrading seals opening a pathway for dilution and eventual loss of the grease, but without opening a sufficient path for oil lubrication.
Those three overlap but let that brief categorization stand, because my point is that none of them is sufficient by itself because none of them explains satisfactorily why so few engines suffer this problem and why those that do may vary from a few thousand miles to nearly a hundred thousand. The last two deal with water build-up creating acids in the oil, so they would be sensitive to the driving style of the owner, and the mechanical certainly would be exacerbated by the occasional lugging in 'gentle' driving. Nevertheless, none of them is fully persuasive as a sole cause. Certainly not my casual speculation about electrolysis, but neither of the other two sells me either. Not exclusively.
I'm beginning to suspect a combination of these effects must be present to initiate the breakdown cascade. Thus, most drivers never drive gently enough for enough months to create the acid problem that leads to the seals hardening enough to cause their mechanical changes under the next high load operation that leads to... Something like that.
Any thoughts?
Gary
#15
12-12-2011, 10:54 PM
Yes, we crossed in the mail, so to speak. I started my reply, went off to take care of Cindy (a stroke victim) and resumed at the editing page without checking the thread for other replies.
Honestly, I'm best at electron movement and all the variations and derivatives of that phenomenon, as I'm often reminded by my nephew. (Little whippersnapper ended up at Scripps doing stuff I don't pretend to keep up with, but I suspect you two could have a lovely conversation about molecular design.) In any case, petroleum engineering is definitely not my field, so I'll accept your information without quibble.
I'm curious whether the soap thickener doesn't have some effect on the lubricating properties of the oil component. I don't offer a demurrer you understand, just curiosity. And personally, I could accept the oil providing equally effective lubrication of a bearing when it's present in the required quantity to stay in the correct operating temperature range. But I'd worry that a bearing in the axle style in a location intended for grease-lubrication would have that supply of oil. Granted, it is located where the oil supply is potentially available, but I'd worry about drain down when I don't drive for several days. Am I being obsessive here?
Honestly, I'm best at electron movement and all the variations and derivatives of that phenomenon, as I'm often reminded by my nephew. (Little whippersnapper ended up at Scripps doing stuff I don't pretend to keep up with, but I suspect you two could have a lovely conversation about molecular design.) In any case, petroleum engineering is definitely not my field, so I'll accept your information without quibble.
I'm curious whether the soap thickener doesn't have some effect on the lubricating properties of the oil component. I don't offer a demurrer you understand, just curiosity. And personally, I could accept the oil providing equally effective lubrication of a bearing when it's present in the required quantity to stay in the correct operating temperature range. But I'd worry that a bearing in the axle style in a location intended for grease-lubrication would have that supply of oil. Granted, it is located where the oil supply is potentially available, but I'd worry about drain down when I don't drive for several days. Am I being obsessive here?
Here is a great quick read on grease http://www.machinerylubrication.com/.../grease-basics
In terms of using oil in an application designed for grease, you are correct, sufficient oil supply is a key factor. This is where my knowledge becomes somewhat limited as it pertains to our engines. I have not seen one of these engines fully pulled apart, but It appears that this particular intermediate shaft is supplied fairly well by oil falling off of the crankshaft bearings. Generally oil is flying everywhere inside a modern engine crankcase
This is why it is quite strange that Porsche chose to use a sealed, greased rolling element bearing in this application. This is even stranger when you consider that the OTHER end of the intermediate shaft has a more traditional force fed plain bearing (like the main bearings, wrist pins, etc, these are all fed through a hole in the bearing and are generally bulletproof if you keep good clean oil running through them). The GT3's and Turbos all have the famed Metzger engine, which I believe uses no rolling element bearings for this very purpose. The use of a rolling element bearing was almost certainly a cost/complexity cutting measure...http://i102.photobucket.com/albums/m.../M96timing.jpg
When you stop the car, the oil does drain off to an extent (if you drive it every few days, this is minimized, but leaving the car in the garage for the winter can potentially have detrimental effects). This is why the cold start is one of the worst things for your engine. Most of the wear occurs during this short period, when the oil pump is rapidly rushing oil to the various lubrication points in the engine. Grease on the other hand DOES allow for essentially "instant" lubrication.
Yes, one always has to keep a little skepticism when listening to the barker for a product. Some can be coldly objective because they're selling something that honestly isn't available at the big box store, so to speak. Well, perhaps warmly objective, but I mean they only need to explain, not persuade. Others have a crowded bazaar of competition and feel the need to overstate. To say the least. Lubricants definitely fall into the latter category.
I'm beginning to notice an interesting aspect of this problem. If we were a Tiger Team allocated to find an answer, or at least pin down a chain of causation, I'd start to assign sub-teams about now. We have plausible candidates in mechanical, electrical, and chemical directions.
The mechanical attempt to explain points the finger at the broad spectrum goal of reducing manufacturing cost with the 996, and specifically the choice of a single-row bearing rather than the double-row that came later. The electrical (in the sense of electron movement, not the wiring harness) sees a potential for electrolysis when so many new alloys were introduced in the design. And of course, the chemical points to degrading seals opening a pathway for dilution and eventual loss of the grease, but without opening a sufficient path for oil lubrication.
Those three overlap but let that brief categorization stand, because my point is that none of them is sufficient by itself because none of them explains satisfactorily why so few engines suffer this problem and why those that do may vary from a few thousand miles to nearly a hundred thousand. The last two deal with water build-up creating acids in the oil, so they would be sensitive to the driving style of the owner, and the mechanical certainly would be exacerbated by the occasional lugging in 'gentle' driving. Nevertheless, none of them is fully persuasive as a sole cause. Certainly not my casual speculation about electrolysis, but neither of the other two sells me either. Not exclusively.
I'm beginning to suspect a combination of these effects must be present to initiate the breakdown cascade. Thus, most drivers never drive gently enough for enough months to create the acid problem that leads to the seals hardening enough to cause their mechanical changes under the next high load operation that leads to... Something like that.
Any thoughts?
Gary
I'm beginning to notice an interesting aspect of this problem. If we were a Tiger Team allocated to find an answer, or at least pin down a chain of causation, I'd start to assign sub-teams about now. We have plausible candidates in mechanical, electrical, and chemical directions.
The mechanical attempt to explain points the finger at the broad spectrum goal of reducing manufacturing cost with the 996, and specifically the choice of a single-row bearing rather than the double-row that came later. The electrical (in the sense of electron movement, not the wiring harness) sees a potential for electrolysis when so many new alloys were introduced in the design. And of course, the chemical points to degrading seals opening a pathway for dilution and eventual loss of the grease, but without opening a sufficient path for oil lubrication.
Those three overlap but let that brief categorization stand, because my point is that none of them is sufficient by itself because none of them explains satisfactorily why so few engines suffer this problem and why those that do may vary from a few thousand miles to nearly a hundred thousand. The last two deal with water build-up creating acids in the oil, so they would be sensitive to the driving style of the owner, and the mechanical certainly would be exacerbated by the occasional lugging in 'gentle' driving. Nevertheless, none of them is fully persuasive as a sole cause. Certainly not my casual speculation about electrolysis, but neither of the other two sells me either. Not exclusively.
I'm beginning to suspect a combination of these effects must be present to initiate the breakdown cascade. Thus, most drivers never drive gently enough for enough months to create the acid problem that leads to the seals hardening enough to cause their mechanical changes under the next high load operation that leads to... Something like that.
Any thoughts?
Gary