Great videos! I bought a 996 a few weeks ago and have been replacing the IMS bearing as well. Your videos have come in handy on more than one occasion + I find your presentation style to be very entertaining and the under-car videos to perfectly, and humorously, encapsulate the reality of DIY car repairs.
You took apart a perfectly good bearing. You have double row bearings meaning you had an early build 2000. The problem bearings came mid-year when Boxsters went to the single row unit, the "problem" unit. The cars that had IMS problems were usually driven at low rpm a lot, instead of keeping cruise rpm around 3000 most of the time in whatever gear. It also had to do with load, speed of the bearing, and frequency of oil changes.
If you haven't worked in engine development, you shouldn't suspect anything, especially not question the ability of the Porsche engineers. They are the best of the best
My friend this is the best theory that I have heard regarding the IMS bearing. And it makes perfect sense. I to believe that the seals are there to keep oil in when spinning and not to keep oil out. Not seen one with any grease in them like everyone thinks there should be. I to believe that the problem could also be the oil quality as in 20,000 or 2 year service is not good enough for the bearing. I think drive regular and change oil regularly every 5,000 miles and used the correct grade. I here people using Miller’s 10w50 which I think is far to thick.
I like your investigation of this issue however 1) FYI, dirty oil is much lower viscosity, not higher viscosity (with synthetic, probably down 28+% after about 5,000 miles if my memory serves me. 2) The main advantage if not only benefit of his kit is that the continous oil flow acts as a heat disipater and cools the bearing, because once the bearing is spinning oil is thrown out before it gets in the bearing.
I haven't heard (1) before. certainly in the long term, it leads to higher viscosity (higher viscosity = thicker), but I could be wrong in the 5k range... I guess I should do more research. (2) I think lubrication is important and a possible contributing factor to failure, but I haven't seen any indication of heat damage in the bearings I've been able to inspect (see my blog if you're curious: burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). Of course, 3 is a pretty small sample size, so hopefully I can keep collecting IMS bearings.
thanks for this video, i'm afraid though that my bearing will go soon. changed the oil today and found copperflakes in the oilfilter. car is a 2003 boxster 2.7liter with the 228ps engine.
how do you lube a bearing ? Pressure, Splash, or sump ( which is perhaps incidental from the lubrication of something else by method 1 or 2.. and it then drains off again..
Nhat Tran because the contaminated engineoil becomes acidic with time, leaving your car stand for several months with the old oil sitting in it, seeping into the bearing, it will cause corrosion inside the bearing and thus will make it wear faster when you drive your car again.
Change you oil before mothballing it for winter...easy insurance. Change it, run the engine a while until it is hot then shut it down and store it. You should be fine. Dont store you car with last years old oil in it no. OIl is cheap, engines aren't. Also, never run ethanol gas in these cars. Store with gas additive and replace your fuel filter once in a while too. Keep your coolant fresh too.
Sealed bearings don't really seal anything in or out. The seals are designed to mostly keep grease in and keep big chunks out. Bearing "seals" are nothing like actual seals. there is no tension between the seal and the inner race. They will allow liquids in fairly easily.
Do R/C! I just can’t believe that these bearings would hold grease in when spinning around in oil, it doesn’t make sense. Oil is thinner than grease so it makes total sense that oil will find its way in, also it would be a lot more difficult to get the seals off if they were to hold the grease in. Everyone I have seen taken off, seam to come off easily which doesn’t look like a good seal to me. I agree oil will work it’s way into the bearing and the seals are there to stop the oil shooting out when spinning. Oil is the key and change it regularly as well as driving it regularly to, this will keep the oil in good condition and the bearing lubricated.
You need to take cutting wheel and cut the bearing open in 2 locations, so you can take it apart and inspect the ball bearings and races. You have a dual row, so did I, my bearing seemed fine when it was unopened, wasn't until i cut it open that i found it's condition, one row of balls completely pitted and on there way to failure, and both rows with inner race pitting/roughening in one spot.
I thought about the same thing, holes in the intermediate shaft, after seeing pedro's (from pedro's garage) video. Now the question is, will those small homes cause other problems?
Oil isn't supposed to enter the intermediate shaft, supposedly due to the harmonic imbalance of having oil slosh around in there. Otherwise Porsche would have just vented the tube from the factory. Even the "open" bearing designs from LN have an inner seal to keep oil out of the shaft.
Quick question for anyone reading i have a 2000 boxster S with 188,000 still running strong my manufacture date is March of 2000 what are the odds my car has the duel row bearing I bought the car from a guy who inherited it from his father who was the only owner he thinks it may have been changed before but not sure the car has been well maintained just wanted a little piece of mind that it has duel row bearing
How refreshing and unlike the Porsche forums, objective and intelligent observations. Good job. I'm going to do this on my 99 996 C2 with 102k this year which has the original IMS. I'm leaning towards the MB Motorsport Roller IMS kit for $360 which includes a spacer for dual row 911 and Boxters. I still think this was a poor design decision on Porches engineers part. A sealed bearing, typical what you would see as wheel bearings only these seals are being constantly attacked by hot engine oil. This design never made sense.
This topic gets insane rather quickly when other observations are brought up so I’ve learned to say out. The forums would have you believe this issue it due to using Porches recommended oil (Mobil One) rather than a design fault. If this theory were true, Mercedes, Audi and BMW's would also be having lubrication related issues since they also endorsed Mobil One. I mean seriously, where is the logic in installing sealed greased bearing which is constantly attacked by hot acidic oil in an internal engine environment? I can only conclude that during this time in Porsche history, they were not doing well financially and this was the cheapest solution rather than costly recasting and retooling for a new block design. After all, it was the Boxter and the 996 that pulled them out of the depths of hell. The Turbo engine 996's of the same years just prove this theory as they are devoid of this insane "German engineering" design.
Oil feed bypass modification will stop this bearing failure. There's nothing wrong with the quality of the bearings themselves. The bearing configuration inside the crankcase causes oil starvation with the inside race stationary on the IMS causing a centrifugal dissipation of oil away from the bearing. Most bearing engineering applications are usually in reverse of this configuration, hence draws the oil toward the bearing instead of the opposite direction.
I think you're right about oil starvation being a factor, but I don't believe it's the only factor. If it were the only factor, wouldn't the single and dual row bearings fail at a similar rate?
Burner's Cars IMO It has nothing to do with the bearings..The bearing with the dual row should last longer in oil starved situation, but that's only putting of failure to a later date. As I explained in my post, the bearing configuration is the primary cause. If Porsche re-engineered the crankcase architecture and configured the outer race fixed instead of the inner race fixed to support the IMS, the oil would be drawn to the bearing instead of away from the bearing. This is why a oil feed bypass to the bearing is the only satisfactory solution to prevent failure..
I see your point regarding oil starvation, but all bearings fail pretty quickly when starved for oil, right? A dual row wouldn't last much longer. Yet the numbers I've heard just don't bear that out. Failure of the single row is roughly 8 times that of the dual row by all the statistics I've heard.
I'm not going to say a IMS will eventually fail but "most" bearings should last 200k IF you change the oil often and keep the revs above 3k at all times. Use Redline 15w50 and I also use Zmax to soak into it. I'm in a club and only one guy with a 2002 Boxster S had a bearing completely fail. Not once have I talked to an owner of a 1997-99 who had a bearing fail. I have a 99 with just over 100k and it's very happy so far but I do plan on installing a new bearing when it comes clutch kit time.
Sealed bearings are not designed for oil to seep in. Oil destroys the grease. I don't think Porsche did any testing of just letting a car sit to see if something will fail. Let the car sit for a few years and then drive it... does anyone test that?
Ah, yeah, Porsche: "our new roadster is ready... but we've got to let it sit in a garage for a few years before its release..." At any rate, I agree: it's clear Porsche wasn't as thorough as it should have been. I've heard conflicting information about the purpose of the seals, but I can tell you that every one of the IMS bearings I've inspected contained only engine oil (see burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). This suggests the grease serves only as a break in aid as the oil works in these from 40k to 100k at least...
I am just using my automotive technology education and my engineering education to base my knowledge of sealed bearings. I only have the education and not the practical experience however, so there may be sealed bearings that are supposed to let oil in. I have just never heard of a sealed bearing that was supposed to let anything in (or out). Not much of a seal if it did. But at least they used a ball bearing and not a sleeve/solid bearing or something like that. but having the oil right there may have been alright for a sleeve bearing (as long as they forced oil into it somehow).
Ah, yeah, you definitely have more training than I do. Based on my practical experience, the seal definitely does let oil in, and that oil washes out the grease. However, the bearings seem to last for quite some time with just oil as I have not found (or heard) of a single bearing that still had grease in it. At any rate, an oil feed would have improved the system, but with so many theories and factors out there, I doubt there is a single source of all failures.
Thanks for the video. Sorry if I have the same response as others; I haven't read all of them. Here goes: 1) the grease is meant as the primary lubricant for the bearing. Grease has a higher viscosity which keeps the bearing lubricated and from being ejected from the races under high rpm. 2) RC do is right; "sealed" bearings aren't really sealed- the "seals" are more like splash guards. Oil can pass in and out of a sealed bearing, albeit slower than if the bearing was unsealed. My thoughts: the primary culprit is the pollutants in the oil breaking down the grease in the bearing over time. At any one time there is a mixture of oil and grease in the bearing. Upon contact, the pollutants in the oil are breaking down the grease. But, oil will be forced out of the bearing under high rotation. So, cars that are driven more and at high speeds have IMS bearings that essentially retain less oil, which prolongs the life of the grease. For cars that sit and are not driven at high rpm, more oil will be retained in the bearing, which break down the grease faster. And once the grease is gone, it's only a matter of time. The solution: 1)a grease in the bearing that is better suited to sit in acid laden oil. 2) isolation of the bearing from the oil reservoir. 3) keep the bearing oiled at all times (akin to Pedro's method).
It's a good thought, but I've asked around and not a single person has found grease in an IMS bearing they removed from a Porsche... even when the IMSB itself is in pretty good shape. It seems the grease washes out quickly and the bearing depends on oil lubrication. That would also explain why frequent oil changes are so important for the life of the IMS.
Interesting suggestion of design intent. I struggle with the idea that the intent of the engine design engineer was to depend on a non deterministic lubrication method such as oil seeping past a seal and being held there. If they wanted to lubricate the bearings with motor oil it would be better accomplished a directed splash like how some pinion shaft bearings are lubricated in some rear differential or via a pressurized method. It might have been a design mistake that impacted the reliability of the engine, there are many non optimal solutions in many products. If one believes the numbers, 92% of the units with that bearing setup are still okay. But 8% is ridiculously high failure rate in any industry so I am leaning towards a mistake. I had a VW 2.0T FSI with a HPFP that used a flat tappet with a porous coating on it to riding on the cam lobe. I replaced it every 60K mi and the coating was gone and the tappet was well worn by that time. People that ran HPFP that ran higher fuel pressure saw more failures and so did people that ran the 10K oil changes. It didn't work as well as the model or expected. Supplier quality issue may also come into play. The next iteration of the engine used a roller tappet instead and issue went away. Mostly due to the better design, but I am certain it cost way more.
I completely agree that there was some design flaw. The failure rates are just too high! I've heard many theories on the source of the failure. Seals could be a factor, but I don't think it's THE factor for two reasons 1) sealed bearings are used in other oil bath situations (often with transmissions) to protect the bearing from contaminates 2) people have placed bearings without seals and still experienced failures (some single row LN kits have failed). Granted, this is rare, but in my mind it shows it's not all down to the seals.
More food for thought...under higher speeds (high RPM) bearings generally need a lubricant with a lower viscosity; at low speeds a thicker lubricant is preferred. This is from Wikipedia.... If you consider motor oil a "thin" lubricant at operating temp, then it makes sense that cars that get driven hard last longer. You'd have to actually spec out the numbers to see if there is any merit to this theory.
Interesting thought. I wish I knew enough to be able to spec out the bearing with engine oil... that said, it seems all the bearings have engine oil in them (including all three I inspected: burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). There are also all the DOF options, so it seems the engine oil is an acceptable lubricant.
It is an engine oil lubricated bearing ! If you believe anybody uses a permanently lubricated bearing in service like this.. you believe in L.Ron Hubbard and should move slowly away from the computer, toward a safe facility where you can be observed .
I'm in the process of changing my IMS bearing and with all I read about this subject I'm a bit confused with the choice of a replacement. Low runners (my case) are more susceptible of breaking IMS because the oïl infiltred in the bearing is not renewed often enough. For half the price of a 986 used engine, LN engineering offers a kit that sends more oïl in the bearing to be sure it gets fresh oïl all the time but having seals, the bearing should'nt be in contact with engine oïl because of contaminents or debris that could ruin it. For $800 I can buy a kit that I will have to change after only 4 years even if I drove my cars 5000 miles and had oïl change every 1250 miles???? It sound like nobody's wrong and everybody's right. One sure thing is that at the end I'm like many others: feeling guilty not to put enough money to solve that gigantic (sarcastic) menace but many are making a business out of this.
Yeah, exactly! It does seem like a money making opportunity for a bunch of companies! It would be one thing if the kits were perfect, lifetime replacements, but $800 for a kit that has to be replaced every 4 years? Crazy!
Shaking it I will almost you are hearing the balls rattle in the cage not "wear" or "play" between the rollers and races. As for the rest of your theory I am not so sure I would agree. You might be right but for the wrong reasons. Source:bearing guy with 25 years experience and also a CBS certified bearing specialist.
There are several mistakes in this video. First of all a sealed non-maintenance bearing is very common in many industrial applications. Typically they do have a life span though. And yes, it is no surprise to anyone trained into these that grease oil waashes out the grease eventually. Car manufacturers order bearings by tenders and bearing manufacturers offer solutions. Porsche definitely does not buy bearings as parts and assemble them. Bearings come as they are, full packages as specified in tenders. Porsche is known to be very labour and cost guarding manufactrurer and they would never waste time on subcontracted items. (Read the book "The Machine that changed the World"). Third, I've seen that video by Pedro where the bearing "shoots off all oil". There is point there but this video does not convince. What it does definitely show is the if the oil level is too low the bearing will suffer from poor oil supply. Check where the proper oil level is supposed to be...
I was just wondering why you replaced a dual roll bearing with a single roll bearing? The single roll bearing is the one that goes out the most. Here is a link that explains it better. Thanks, and good job. th-cam.com/video/i14LKvAW-So/w-d-xo.html
1:30 I like how you preface the talk about this being your car by stating the following information is not purely factual. I am going to make the assumption that it was NOT your car.
Porsche fucked up. Bottom line. Stupid mistake really. The bearing used grease, making it a lifetime bearing. Something that is relatively new by way of new greases that do not evaporate at temperature. In engines that sit the oil eventually turns acidic and brakes the boundary layer. The bearing should have direct flow of oil under pressure. Stupid mistake.
Yeah. Definitely a design flaw. I don't think it's all down to lubrication since the single row fails at much higher rates than the dual row, but there's definitely a mistake regardless.
Great videos! I bought a 996 a few weeks ago and have been replacing the IMS bearing as well. Your videos have come in handy on more than one occasion + I find your presentation style to be very entertaining and the under-car videos to perfectly, and humorously, encapsulate the reality of DIY car repairs.
You took apart a perfectly good bearing. You have double row bearings meaning you had an early build 2000. The problem bearings came mid-year when Boxsters went to the single row unit, the "problem" unit. The cars that had IMS problems were usually driven at low rpm a lot, instead of keeping cruise rpm around 3000 most of the time in whatever gear. It also had to do with load, speed of the bearing, and frequency of oil changes.
If you haven't worked in engine development, you shouldn't suspect anything, especially not question the ability of the Porsche engineers. They are the best of the best
Except when it comes to IMS failures, D-chunking, bore-scoring, cooling, cam-chain guide wear and catching fire.
My friend this is the best theory that I have heard regarding the IMS bearing. And it makes perfect sense. I to believe that the seals are there to keep oil in when spinning and not to keep oil out.
Not seen one with any grease in them like everyone thinks there should be. I to believe that the problem could also be the oil quality as in 20,000 or 2 year service is not good enough for the bearing.
I think drive regular and change oil regularly every 5,000 miles and used the correct grade. I here people using Miller’s 10w50 which I think is far to thick.
I like your investigation of this issue however
1) FYI, dirty oil is much lower viscosity, not higher viscosity (with synthetic, probably down 28+% after about 5,000 miles if my memory serves me.
2) The main advantage if not only benefit of his kit is that the continous oil flow acts as a heat disipater and cools the bearing, because once the bearing is spinning oil is thrown out before it gets in the bearing.
I haven't heard (1) before. certainly in the long term, it leads to higher viscosity (higher viscosity = thicker), but I could be wrong in the 5k range... I guess I should do more research. (2) I think lubrication is important and a possible contributing factor to failure, but I haven't seen any indication of heat damage in the bearings I've been able to inspect (see my blog if you're curious: burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). Of course, 3 is a pretty small sample size, so hopefully I can keep collecting IMS bearings.
Thanks for stopping by and sharing your thoughts, btw!
thanks for this video, i'm afraid though that my bearing will go soon. changed the oil today and found copperflakes in the oilfilter. car is a 2003 boxster 2.7liter with the 228ps engine.
how do you lube a bearing ? Pressure, Splash, or sump ( which is perhaps incidental from the lubrication of something else by method 1 or 2.. and it then drains off again..
This is educational. Thx! Does this mean storing those Porsches over a couple months of snowy winter will run a high risk of IMS failure?
Nhat Tran because the contaminated engineoil becomes acidic with time, leaving your car stand for several months with the old oil sitting in it, seeping into the bearing, it will cause corrosion inside the bearing and thus will make it wear faster when you drive your car again.
Change you oil before mothballing it for winter...easy insurance. Change it, run the engine a while until it is hot then shut it down and store it. You should be fine. Dont store you car with last years old oil in it no. OIl is cheap, engines aren't. Also, never run ethanol gas in these cars. Store with gas additive and replace your fuel filter once in a while too. Keep your coolant fresh too.
Sealed bearings don't really seal anything in or out. The seals are designed to mostly keep grease in and keep big chunks out. Bearing "seals" are nothing like actual seals. there is no tension between the seal and the inner race. They will allow liquids in fairly easily.
Thanks! I thought that was the case, but I've heard so many other opinions on the subject.
Do R/C! I just can’t believe that these bearings would hold grease in when spinning around in oil, it doesn’t make sense. Oil is thinner than grease so it makes total sense that oil will find its way in, also it would be a lot more difficult to get the seals off if they were to hold the grease in. Everyone I have seen taken off, seam to come off easily which doesn’t look like a good seal to me. I agree oil will work it’s way into the bearing and the seals are there to stop the oil shooting out when spinning. Oil is the key and change it regularly as well as driving it regularly to, this will keep the oil in good condition and the bearing lubricated.
what kind of pie was it?
Thanks for your videos Professor! 😀
Thank you! Porsche Professor... it has a ring to it ;)
You need to take cutting wheel and cut the bearing open in 2 locations, so you can take it apart and inspect the ball bearings and races. You have a dual row, so did I, my bearing seemed fine when it was unopened, wasn't until i cut it open that i found it's condition, one row of balls completely pitted and on there way to failure, and both rows with inner race pitting/roughening in one spot.
Thanks for the suggestion. I cut open the bearing and will be posting results soon.
WHAT an awesome video
I thought about the same thing, holes in the intermediate shaft, after seeing pedro's (from pedro's garage) video. Now the question is, will those small homes cause other problems?
Oil isn't supposed to enter the intermediate shaft, supposedly due to the harmonic imbalance of having oil slosh around in there. Otherwise Porsche would have just vented the tube from the factory. Even the "open" bearing designs from LN have an inner seal to keep oil out of the shaft.
We could sell it as an IMS Solution for $1700!!! Oh, wait...
Quick question for anyone reading i have a 2000 boxster S with 188,000 still running strong my manufacture date is March of 2000 what are the odds my car has the duel row bearing I bought the car from a guy who inherited it from his father who was the only owner he thinks it may have been changed before but not sure the car has been well maintained just wanted a little piece of mind that it has duel row bearing
How refreshing and unlike the Porsche forums, objective and intelligent observations. Good job. I'm going to do this on my 99 996 C2 with 102k this year which has the original IMS. I'm leaning towards the MB Motorsport Roller IMS kit for $360 which includes a spacer for dual row 911 and Boxters. I still think this was a poor design decision on Porches engineers part. A sealed bearing, typical what you would see as wheel bearings only these seals are being constantly attacked by hot engine oil. This design never made sense.
Thanks! I've spent my fair share of time on those forums, and I know exactly what you mean. I think people get way too dogmatic about these things!
This topic gets insane rather quickly when other observations are brought up so I’ve learned to say out. The forums would have you believe this issue it due to using Porches recommended oil (Mobil One) rather than a design fault. If this theory were true, Mercedes, Audi and BMW's would also be having lubrication related issues since they also endorsed Mobil One. I mean seriously, where is the logic in installing sealed greased bearing which is constantly attacked by hot acidic oil in an internal engine environment? I can only conclude that during this time in Porsche history, they were not doing well financially and this was the cheapest solution rather than costly recasting and retooling for a new block design. After all, it was the Boxter and the 996 that pulled them out of the depths of hell. The Turbo engine 996's of the same years just prove this theory as they are devoid of this insane "German engineering" design.
Oil feed bypass modification will stop this bearing failure. There's nothing wrong with the quality of the bearings themselves. The bearing configuration inside the crankcase causes oil starvation with the inside race stationary on the IMS causing a centrifugal dissipation of oil away from the bearing. Most bearing engineering applications are usually in reverse of this configuration, hence draws the oil toward the bearing instead of the opposite direction.
I think you're right about oil starvation being a factor, but I don't believe it's the only factor. If it were the only factor, wouldn't the single and dual row bearings fail at a similar rate?
Burner's Cars
IMO It has nothing to do with the bearings..The bearing with the dual row should last longer in oil starved situation, but that's only putting of failure to a later date. As I explained in my post, the bearing configuration is the primary cause. If Porsche re-engineered the crankcase architecture and configured the outer race fixed instead of the inner race fixed to support the IMS, the oil would be drawn to the bearing instead of away from the bearing. This is why a oil feed bypass to the bearing is the only satisfactory solution to prevent failure..
I see your point regarding oil starvation, but all bearings fail pretty quickly when starved for oil, right? A dual row wouldn't last much longer. Yet the numbers I've heard just don't bear that out. Failure of the single row is roughly 8 times that of the dual row by all the statistics I've heard.
I'm not going to say a IMS will eventually fail but "most" bearings should last 200k IF you change the oil often and keep the revs above 3k at all times. Use Redline 15w50 and I also use Zmax to soak into it. I'm in a club and only one guy with a 2002 Boxster S had a bearing completely fail. Not once have I talked to an owner of a 1997-99 who had a bearing fail. I have a 99 with just over 100k and it's very happy so far but I do plan on installing a new bearing when it comes clutch kit time.
do you think thinner oil say 0w-40...would migrate into the bearing easier.......im using 15w-50, now i worry its to thick to get into the bearing
Sealed bearings are not designed for oil to seep in. Oil destroys the grease.
I don't think Porsche did any testing of just letting a car sit to see if something will fail. Let the car sit for a few years and then drive it... does anyone test that?
Ah, yeah, Porsche: "our new roadster is ready... but we've got to let it sit in a garage for a few years before its release..." At any rate, I agree: it's clear Porsche wasn't as thorough as it should have been.
I've heard conflicting information about the purpose of the seals, but I can tell you that every one of the IMS bearings I've inspected contained only engine oil (see burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). This suggests the grease serves only as a break in aid as the oil works in these from 40k to 100k at least...
I am just using my automotive technology education and my engineering education to base my knowledge of sealed bearings. I only have the education and not the practical experience however, so there may be sealed bearings that are supposed to let oil in. I have just never heard of a sealed bearing that was supposed to let anything in (or out). Not much of a seal if it did. But at least they used a ball bearing and not a sleeve/solid bearing or something like that. but having the oil right there may have been alright for a sleeve bearing (as long as they forced oil into it somehow).
Ah, yeah, you definitely have more training than I do. Based on my practical experience, the seal definitely does let oil in, and that oil washes out the grease. However, the bearings seem to last for quite some time with just oil as I have not found (or heard) of a single bearing that still had grease in it. At any rate, an oil feed would have improved the system, but with so many theories and factors out there, I doubt there is a single source of all failures.
Thanks for the video. Sorry if I have the same response as others; I haven't read all of them. Here goes: 1) the grease is meant as the primary lubricant for the bearing. Grease has a higher viscosity which keeps the bearing lubricated and from being ejected from the races under high rpm. 2) RC do is right; "sealed" bearings aren't really sealed- the "seals" are more like splash guards. Oil can pass in and out of a sealed bearing, albeit slower than if the bearing was unsealed. My thoughts: the primary culprit is the pollutants in the oil breaking down the grease in the bearing over time. At any one time there is a mixture of oil and grease in the bearing. Upon contact, the pollutants in the oil are breaking down the grease. But, oil will be forced out of the bearing under high rotation. So, cars that are driven more and at high speeds have IMS bearings that essentially retain less oil, which prolongs the life of the grease. For cars that sit and are not driven at high rpm, more oil will be retained in the bearing, which break down the grease faster. And once the grease is gone, it's only a matter of time. The solution: 1)a grease in the bearing that is better suited to sit in acid laden oil. 2) isolation of the bearing from the oil reservoir. 3) keep the bearing oiled at all times (akin to Pedro's method).
It's a good thought, but I've asked around and not a single person has found grease in an IMS bearing they removed from a Porsche... even when the IMSB itself is in pretty good shape. It seems the grease washes out quickly and the bearing depends on oil lubrication. That would also explain why frequent oil changes are so important for the life of the IMS.
Interesting suggestion of design intent.
I struggle with the idea that the intent of the engine design engineer was to depend on a non deterministic lubrication method such as oil seeping past a seal and being held there. If they wanted to lubricate the bearings with motor oil it would be better accomplished a directed splash like how some pinion shaft bearings are lubricated in some rear differential or via a pressurized method. It might have been a design mistake that impacted the reliability of the engine, there are many non optimal solutions in many products. If one believes the numbers, 92% of the units with that bearing setup are still okay. But 8% is ridiculously high failure rate in any industry so I am leaning towards a mistake.
I had a VW 2.0T FSI with a HPFP that used a flat tappet with a porous coating on it to riding on the cam lobe. I replaced it every 60K mi and the coating was gone and the tappet was well worn by that time. People that ran HPFP that ran higher fuel pressure saw more failures and so did people that ran the 10K oil changes. It didn't work as well as the model or expected. Supplier quality issue may also come into play. The next iteration of the engine used a roller tappet instead and issue went away. Mostly due to the better design, but I am certain it cost way more.
I completely agree that there was some design flaw. The failure rates are just too high! I've heard many theories on the source of the failure. Seals could be a factor, but I don't think it's THE factor for two reasons 1) sealed bearings are used in other oil bath situations (often with transmissions) to protect the bearing from contaminates 2) people have placed bearings without seals and still experienced failures (some single row LN kits have failed). Granted, this is rare, but in my mind it shows it's not all down to the seals.
You only need the tiniest amount of oil to lubricate these bearings.
More food for thought...under higher speeds (high RPM) bearings generally need a lubricant with a lower viscosity; at low speeds a thicker lubricant is preferred. This is from Wikipedia.... If you consider motor oil a "thin" lubricant at operating temp, then it makes sense that cars that get driven hard last longer. You'd have to actually spec out the numbers to see if there is any merit to this theory.
Interesting thought. I wish I knew enough to be able to spec out the bearing with engine oil... that said, it seems all the bearings have engine oil in them (including all three I inspected: burnerscars.blogspot.com/2016/08/porsche-ims-bearing-inspection.html). There are also all the DOF options, so it seems the engine oil is an acceptable lubricant.
It is an engine oil lubricated bearing ! If you believe anybody uses a permanently lubricated bearing in service like this.. you believe in L.Ron Hubbard and should move slowly away from the computer, toward a safe facility where you can be observed .
I'm in the process of changing my IMS bearing and with all I read about this subject I'm a bit confused with the choice of a replacement. Low runners (my case) are more susceptible of breaking IMS because the oïl infiltred in the bearing is not renewed often enough. For half the price of a 986 used engine, LN engineering offers a kit that sends more oïl in the bearing to be sure it gets fresh oïl all the time but having seals, the bearing should'nt be in contact with engine oïl because of contaminents or debris that could ruin it. For $800 I can buy a kit that I will have to change after only 4 years even if I drove my cars 5000 miles and had oïl change every 1250 miles???? It sound like nobody's wrong and everybody's right. One sure thing is that at the end I'm like many others: feeling guilty not to put enough money to solve that gigantic (sarcastic) menace but many are making a business out of this.
Yeah, exactly! It does seem like a money making opportunity for a bunch of companies! It would be one thing if the kits were perfect, lifetime replacements, but $800 for a kit that has to be replaced every 4 years? Crazy!
Shaking it I will almost you are hearing the balls rattle in the cage not "wear" or "play" between the rollers and races. As for the rest of your theory I am not so sure I would agree. You might be right but for the wrong reasons. Source:bearing guy with 25 years experience and also a CBS certified bearing specialist.
good point about the cage rattling! I'd love to hear more about your thoughts on the bearing. You certainly have more experience and knowledge than I.
There are several mistakes in this video. First of all a sealed non-maintenance bearing is very common in many industrial applications. Typically they do have a life span though. And yes, it is no surprise to anyone trained into these that grease oil waashes out the grease eventually.
Car manufacturers order bearings by tenders and bearing manufacturers offer solutions. Porsche definitely does not buy bearings as parts and assemble them. Bearings come as they are, full packages as specified in tenders. Porsche is known to be very labour and cost guarding manufactrurer and they would never waste time on subcontracted items. (Read the book "The Machine that changed the World").
Third, I've seen that video by Pedro where the bearing "shoots off all oil". There is point there but this video does not convince. What it does definitely show is the if the oil level is too low the bearing will suffer from poor oil supply. Check where the proper oil level is supposed to be...
Pedro is just pushing his kits, of course.
IMS bearing failures, water pump, WTF?. Bloody nightmare!
Miata MX 5, build far superior for a roadster.
I was just wondering why you replaced a dual roll bearing with a single roll bearing? The single roll bearing is the one that goes out the most. Here is a link that explains it better. Thanks, and good job. th-cam.com/video/i14LKvAW-So/w-d-xo.html
1:30 I like how you preface the talk about this being your car by stating the following information is not purely factual.
I am going to make the assumption that it was NOT your car.
Porsche fucked up. Bottom line. Stupid mistake really. The bearing used grease, making it a lifetime bearing. Something that is relatively new by way of new greases that do not evaporate at temperature. In engines that sit the oil eventually turns acidic and brakes the boundary layer. The bearing should have direct flow of oil under pressure. Stupid mistake.
Yeah. Definitely a design flaw. I don't think it's all down to lubrication since the single row fails at much higher rates than the dual row, but there's definitely a mistake regardless.