IMS Failure at 51,000 miles - NOW WHAT?!
08-31-2012, 02:22 PM
#16
This "certified" (which, BTW means he pays LN to be on the "certified" list) mechanic should have known rule #1 from LN eng, - any engine that has already suffered an IMS failure is NOT a candidate for IMS retrofit, because of all the misc metal particles floating around in the engine.
Have to disagree with the above comments.
First of all, the original IMS bearing is a sealed bearing and no amount of uber high revs is going to get any lube into the bearing. Maybe once the bearing has already begun to fail and the seals have become compromised, maybe some lube would get to the bearing, but it's already too late at that point.
So high revs is not what the IMS needs to survive. Getting the engine nice and hot every time it is started, is what I firmly believe to be the answer to IMS health. (high revs WILL help get you there, but is not what is actually helping the bearing) This will boil away the moisture that can accumulate inside an engine when it is used for short trips. If any of this moisture collects in the bearing then corrosion begins on the finely polished surfaces inside the bearing. Once that happens just one time, it is the beginning of the end for the IMS bearing.
I think this is exactly where your problem came from. All it took was a little bit of moisture to get in the bearing and then the corrosion process begins, uninterrupted with the engine just sitting. In six months the corrosion can do some serious damage inside this bearing. Once the degradation of the bearing has begun it is just a matter of time and miles until total meltdown.
Have to disagree with the above comments.
First of all, the original IMS bearing is a sealed bearing and no amount of uber high revs is going to get any lube into the bearing. Maybe once the bearing has already begun to fail and the seals have become compromised, maybe some lube would get to the bearing, but it's already too late at that point.
So high revs is not what the IMS needs to survive. Getting the engine nice and hot every time it is started, is what I firmly believe to be the answer to IMS health. (high revs WILL help get you there, but is not what is actually helping the bearing) This will boil away the moisture that can accumulate inside an engine when it is used for short trips. If any of this moisture collects in the bearing then corrosion begins on the finely polished surfaces inside the bearing. Once that happens just one time, it is the beginning of the end for the IMS bearing.
I think this is exactly where your problem came from. All it took was a little bit of moisture to get in the bearing and then the corrosion process begins, uninterrupted with the engine just sitting. In six months the corrosion can do some serious damage inside this bearing. Once the degradation of the bearing has begun it is just a matter of time and miles until total meltdown.
On 2006-2008 987.1's (especially 2008), it's a judgment call as IMS bearing is highly unlikely to fail and the cost of upgrading is steep (have to drop the engine and split the case).
08-31-2012, 03:32 PM
#17
I just changed out the IMSB on my '04 Boxster @ 65k miles. The bearing and it's seals all looked and felt like it had just been installed the previous day. That bearing was in like new condition. The seals were still beautiful. If the seals themselves were prone to falling apart wouldn't there be at least some trace of wear and tear after 65k miles and 8 years? I'm pretty sure there would be. And what about IMS failure at less than 10k miles? The seals are surely not failing that early.
The high revs theory is mostly internet folk-lore. I'm a firm believer that it is moisture that is killing these IMS bearings and NOT a lack of lubrication.
The grease gets washed away and you need high RPM's to lubricate the bearing with hot oil instead. In other words, the bearing doesn't necessarily need an immediate upgrade when the seal breaks - "driving the **** out of it" will continue to protect the bearing (though, yes, on the initial IMS bearing design you're better off upgrading sooner than later).
On 2006-2008 987.1's (especially 2008), it's a judgment call as IMS bearing is highly unlikely to fail and the cost of upgrading is steep (have to drop the engine and split the case).
On 2006-2008 987.1's (especially 2008), it's a judgment call as IMS bearing is highly unlikely to fail and the cost of upgrading is steep (have to drop the engine and split the case).
For the post '05 engines with the larger bearing there is no "upgrade" to be done. No one sells a bearing for this.
08-31-2012, 03:40 PM
#18
Drifting
I still don't believe even in this. I think the seal only goes out AFTER the bearing has begun it's degradation. The unwanted axial movement of the bearing then takes out the seal.
I just changed out the IMSB on my '04 Boxster @ 65k miles. The bearing and it's seals all looked and felt like it had just been installed the previous day. That bearing was in like new condition. The seals were still beautiful. If the seals themselves were prone to falling apart wouldn't there be at least some trace of wear and tear after 65k miles and 8 years? I'm pretty sure there would be. And what about IMS failure at less than 10k miles? The seals are surely not failing that early.
The high revs theory is mostly internet folk-lore. I'm a firm believer that it is moisture that is killing these IMS bearings and NOT a lack of lubrication.
I just changed out the IMSB on my '04 Boxster @ 65k miles. The bearing and it's seals all looked and felt like it had just been installed the previous day. That bearing was in like new condition. The seals were still beautiful. If the seals themselves were prone to falling apart wouldn't there be at least some trace of wear and tear after 65k miles and 8 years? I'm pretty sure there would be. And what about IMS failure at less than 10k miles? The seals are surely not failing that early.
The high revs theory is mostly internet folk-lore. I'm a firm believer that it is moisture that is killing these IMS bearings and NOT a lack of lubrication.
The RPM theory was proposed by a well-regarded shop that did a lot of IMS post-mortems; I'll see if I can find the thread.
Edit: found it. https://rennlist.com/forums/987-981-...?highlight=IMS
Portion of the post is copied here, emphasis mine:
Why do intermediate shafts fail (or rather, why do the bearings fail)?
Thanks to a fellow Porsche Boxster owner who is also a retired bearing engineer who worked for Timken Bearing, we have gained much insight towards the root causes of intermediate shaft failures. Here's the reader's digest version of his bearing analysis and how LN Engineering has used this information in developing its IMS solutions. By their estimates, they figure a 90% survival rate of the bearing used in the IMS at 90,000 miles* - resulting in a staggering 10% failure rate (called the Ll0 life)! *Assuming an average speed of 60mph in top gear.
There are two configurations of intermediate shafts – the major variations are in the drive, where the early have a bicycle chain style sprocket where the later is a gear type sprocket. The other differences are in the intermediate shaft bearing configurations, with three bearing configurations - an early dual row, single row, then final version, with the larger single row bearing.
Both intermediate shaft assemblies use a bearing support visible as a small stud from the exterior of the engine in the center of the IMS hub flange. This stud has a flange that centers and rests on the inboard side of the bearing and torques the inner race to the stationary IMS hub flange. The outer race is allowed to rotate which allows the IMS to rotate. A few problems stem from the support stud which is undercut for an o-ring to keep oil from leaking out of the IMS hub flange. This severely weakens the stud as it is undercut deeper than the threads by a good margin. The main problem stems from the use of a sealed bearing. Although the seals are intended to keep oil out of the IMS tube and keep the permanent lubricant in the bearing, neither happens.
On engines observant of factory recommended long drain intervals, oil heavily laden from fuel or just dirty from too long of drain intervals provides poor lubrication for the IMS bearing. Even .002% water in the oil can reduce bearing life by up to 48%. Higher moisture levels up to 6% can reduce bearing life by up to 83%. Excessive oil temperatures also have a negative effect on bearing life - the life of the permanent lubricant used in these bearings is cut in half by every 18F increase in temperature - from an uncontaminated life of up to 30 years at 86F to a useful life of only 90 days at 212F! This is why the bearing engineer recommended removing the seal and allowing the engine oil to lubricate the bearing, and why frequent changes are so important. Oils high in ZDDP and moly further improve longevity as suggested in the article referenced above. More info about ball bearings can be found here.
Now it gets more technical.... Where the exact reason for IMS failures cannot be known for sure, in the bearing analysis it was noted that bearings used in the IMS position are unusual in that they are double sealed and have outer race rotation. Bearings were found to be void of grease and had light oil in them and wear patterns in the ball grooves indicate marginal lubrication due to the relatively low viscosity of motor oil compared to grease.
In addition, conventional class 1 bearings, like the 52100-series bearing steel used in the factory bearings, is typically only stable to 250F, suffering from fatigue and weakening exposed to elevated engine temperatures that slowly affect the bearing's strength over its lifespan. Attempting to reduce engine coolant operating temperatures directly reduces oil temperatures, further improving bearing life! That's why trying to lower the coolant AND oil temperature is so important!
Computer simulation of the 6204 bearing showed that only three ***** are under load at any given time. Hertz stress is moderate. Lube film thickness is very small. Ideally it should be greater than the worst surface finish. Speed is not high enough to develop an elastohydrodynamic film to overcome surface finish/film issue. Fatigue life is high due to relative light load but with no EHD film there will be metal/metal contact and wear. With only three ***** under load at any one time the unloaded ***** will be dragged around by the ball separator. When a ball leaves the loaded zone it will tend to be driven into the separator pocket.
The engineer’s initial thoughts were that the ball-separator failure led to bearing collapse, but after analysis of said IMS bearings, it would appear that bearing wear/fatigue spalls lead to separator wear and outer race failure. Separator failure and bearing collapse causes catastrophic failure of the mounting bolt(s) and IMS/timing chain components. The first recommendation was to use a bearing without seals and secondly to use a higher viscosity oil (with greater film strength). More frequent changes will also improve lubrication quality. An oil with extreme pressure additives like Moly might also further assist in increasing bearing life. Higher rpms also increases bearing life as this lessens the viscosity requirements of the lubricant to maintain EHD lubrication, also providing a reasonable explanation of the lack of IMS failures in tracked cars or those driven "like they were stolen." Likewise, far more failures are found in engines with low mileage that are garage queens and never driven to their full protential. Further recommendations by the retired Timken engineer are evident in the design of LN Engineering’s IMS upgrade and retrofit kits.
Thanks to a fellow Porsche Boxster owner who is also a retired bearing engineer who worked for Timken Bearing, we have gained much insight towards the root causes of intermediate shaft failures. Here's the reader's digest version of his bearing analysis and how LN Engineering has used this information in developing its IMS solutions. By their estimates, they figure a 90% survival rate of the bearing used in the IMS at 90,000 miles* - resulting in a staggering 10% failure rate (called the Ll0 life)! *Assuming an average speed of 60mph in top gear.
There are two configurations of intermediate shafts – the major variations are in the drive, where the early have a bicycle chain style sprocket where the later is a gear type sprocket. The other differences are in the intermediate shaft bearing configurations, with three bearing configurations - an early dual row, single row, then final version, with the larger single row bearing.
Both intermediate shaft assemblies use a bearing support visible as a small stud from the exterior of the engine in the center of the IMS hub flange. This stud has a flange that centers and rests on the inboard side of the bearing and torques the inner race to the stationary IMS hub flange. The outer race is allowed to rotate which allows the IMS to rotate. A few problems stem from the support stud which is undercut for an o-ring to keep oil from leaking out of the IMS hub flange. This severely weakens the stud as it is undercut deeper than the threads by a good margin. The main problem stems from the use of a sealed bearing. Although the seals are intended to keep oil out of the IMS tube and keep the permanent lubricant in the bearing, neither happens.
On engines observant of factory recommended long drain intervals, oil heavily laden from fuel or just dirty from too long of drain intervals provides poor lubrication for the IMS bearing. Even .002% water in the oil can reduce bearing life by up to 48%. Higher moisture levels up to 6% can reduce bearing life by up to 83%. Excessive oil temperatures also have a negative effect on bearing life - the life of the permanent lubricant used in these bearings is cut in half by every 18F increase in temperature - from an uncontaminated life of up to 30 years at 86F to a useful life of only 90 days at 212F! This is why the bearing engineer recommended removing the seal and allowing the engine oil to lubricate the bearing, and why frequent changes are so important. Oils high in ZDDP and moly further improve longevity as suggested in the article referenced above. More info about ball bearings can be found here.
Now it gets more technical.... Where the exact reason for IMS failures cannot be known for sure, in the bearing analysis it was noted that bearings used in the IMS position are unusual in that they are double sealed and have outer race rotation. Bearings were found to be void of grease and had light oil in them and wear patterns in the ball grooves indicate marginal lubrication due to the relatively low viscosity of motor oil compared to grease.
In addition, conventional class 1 bearings, like the 52100-series bearing steel used in the factory bearings, is typically only stable to 250F, suffering from fatigue and weakening exposed to elevated engine temperatures that slowly affect the bearing's strength over its lifespan. Attempting to reduce engine coolant operating temperatures directly reduces oil temperatures, further improving bearing life! That's why trying to lower the coolant AND oil temperature is so important!
Computer simulation of the 6204 bearing showed that only three ***** are under load at any given time. Hertz stress is moderate. Lube film thickness is very small. Ideally it should be greater than the worst surface finish. Speed is not high enough to develop an elastohydrodynamic film to overcome surface finish/film issue. Fatigue life is high due to relative light load but with no EHD film there will be metal/metal contact and wear. With only three ***** under load at any one time the unloaded ***** will be dragged around by the ball separator. When a ball leaves the loaded zone it will tend to be driven into the separator pocket.
The engineer’s initial thoughts were that the ball-separator failure led to bearing collapse, but after analysis of said IMS bearings, it would appear that bearing wear/fatigue spalls lead to separator wear and outer race failure. Separator failure and bearing collapse causes catastrophic failure of the mounting bolt(s) and IMS/timing chain components. The first recommendation was to use a bearing without seals and secondly to use a higher viscosity oil (with greater film strength). More frequent changes will also improve lubrication quality. An oil with extreme pressure additives like Moly might also further assist in increasing bearing life. Higher rpms also increases bearing life as this lessens the viscosity requirements of the lubricant to maintain EHD lubrication, also providing a reasonable explanation of the lack of IMS failures in tracked cars or those driven "like they were stolen." Likewise, far more failures are found in engines with low mileage that are garage queens and never driven to their full protential. Further recommendations by the retired Timken engineer are evident in the design of LN Engineering’s IMS upgrade and retrofit kits.
Last edited by sjfehr; 08-31-2012 at 04:04 PM.
08-31-2012, 05:30 PM
#19
Race Director
And there might be another but I'd have to interview the service manager/techs to ascertain as best I could if I would feel comfortable having the shop undertake this job. I might add I would not even consider doing the interview if I believed I'd find the shop not suitable.
The interview would be primarly to help calm my fears/concerns, get a handle on what's involved and of course this includes some pretty firm quote.
Which brings me to a side note. I was at a Porsche dealer some time back and learned that one of the senior techs was going away for a week for training.
Well, more testing that training. The testing was to renew his 'gold' tech certification. There is gold, silver and bronze. This certification has to be renewed every so often (every year, or maybe every two years, I am not sure).
The process to renew (or get this classification) consists of hours of study (monitored by computer) and progress is checked by periodic audited tests, with the final test done at a Porsche site/lab down in southern CA.
In this final test the tech is given an engine -- he doesn't know beforehand which engine -- and this engine has been given a problem and the tech has no clue as to what the problem is.
Using his diagnostics skills and tools and test equipment (I believe he is provided with a standard set of Porsche tools, Porsche test equipment, etc.) he must identify the problem, and fix it and do so right and in the time allotted.
If he is successful he keeps (or gets) his gold certificate which means he makes more money, and of course there's the prestige factor too.
If a tech had this gold certification I would I think trust him to do the engine rebuild provided of course my interview went well, and the service department/tech indicated they were interested in the rebuild.
Not all dealer service departments I would hazard a guess are interested in this 'heavy' duty work.
Anyhow, the only dealer I have come across in which an engine rebuild was underway was at Rector Porsche in Burlingame, CA. I walked in to the service area -- I sometimes have some pretty good access to these areas -- and spotted a 996 engine apart and its cases and parts laying about (covered with shop towels).
(I took a bunch of pics of this engine and its parts and posted them in a post some time back. The pics I think are stored in my personal space on this site and may still be visible.)
The tech said the engine suffered an IMS bearing failure at about 20K miles. It was clear from the condition of the IMS and its bearing race the bearing was toast as was the IMS.
The tech told me though his tear down/inspection of the engine found that within the guidelines Porsche has the engine was suitable for a rebuild.
The tech reported no other collateral damage other than a camchain rail's composite plastic covering had cracked. (The tech reported the owner shut off the engine at the first signs/sounds of trouble.)
The tech said that with a new IMS and its bearing, a new camchain rail and of course some clean up (the cases were already cleaned and the IMS bearing debris didn't make it into the clean/high pressure portion of the engine's oiling system) the engine would be fine.
I was back the next day or the day after and asked about the car. The tech told me that parts had come in and he had reassembled the engine, installed it back in the car and after having subjected it to a bay test then a test drive and found everything good (operating to Porsche standards I think the official wording is) and the car was on the roof (of the dealership) awaiting the customer to come and pick up the car.
Sincerely,
Macster.
08-31-2012, 05:46 PM
#20
IF Boxsters that are raced see reduced IMS failures my hypothesis is that it is because the engine is always fully warmed up to high temps keeping the interior of the engine moisture free. (or free'er)
In your "experts" explanation they say keeping water and oil temps down is important for bearing health. Well guess what? Those same racing Boxsters that are seeing low IMSB failures are seeing sky high temps of their water and oil. He forgot to mention this. A hot crankcase is a dry crankcase. A dry crankcase is a happy environment for the IMSB.
08-31-2012, 07:21 PM
#21
Anyway, I'm not surprised that your bearing and seal looked perfect. Many 986 owners have reported the same when they had theirs replaced with LN units. It's the fact that you never know "when" it may fail that drives people to upgrade them (and at the relative cost, no brainer!).
I think LN makes bearings for 987's as well, it's just a PITA and $$$ to put them in... probably not worth it given that the upgraded bearings in 987's (with the exception of some 2005 Boxsters) are highly unlikely to fail. I question when some indies say "IMS failure" in a 987... they may be making a conjecture based on their previous 996/986 experience.
08-31-2012, 07:40 PM
#22
Drifting
If there is any air inside the bearing there is also moisture. The moisture then condenses out of the air and onto the bearing. The Seals are probably not air tight and allow a small amount of air to be exchanged in the bearing bringing in more moisture.
IF Boxsters that are raced see reduced IMS failures my hypothesis is that it is because the engine is always fully warmed up to high temps keeping the interior of the engine moisture free. (or free'er)
In your "experts" explanation they say keeping water and oil temps down is important for bearing health. Well guess what? Those same racing Boxsters that are seeing low IMSB failures are seeing sky high temps of their water and oil. He forgot to mention this. A hot crankcase is a dry crankcase. A dry crankcase is a happy environment for the IMSB.
IF Boxsters that are raced see reduced IMS failures my hypothesis is that it is because the engine is always fully warmed up to high temps keeping the interior of the engine moisture free. (or free'er)
In your "experts" explanation they say keeping water and oil temps down is important for bearing health. Well guess what? Those same racing Boxsters that are seeing low IMSB failures are seeing sky high temps of their water and oil. He forgot to mention this. A hot crankcase is a dry crankcase. A dry crankcase is a happy environment for the IMSB.
08-31-2012, 08:54 PM
#23
Drifting
If you sell -- I'm interested in buying.
I PM'd you,
Mike
I PM'd you,
Mike
09-01-2012, 02:36 PM
#24
5th Gear
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OK guys, now it get's interesting!
I was quoted around $1500 for the engine swap from my Indi, fantastic.
Now we are considering the following:
2.7l with 53k miles on it + IMS update + Clutch for 11k
or
2.7l > 3.4l conversion with 8k miles on it
The remaining questions are:
What does it take to marry a 3.4l (M97.21) from a 2008, with a 5-speed plus any extra's (exhaust, dme/ecu)?
Remember I have an 05' 987
Has anyone does this successfully?
I was quoted around $1500 for the engine swap from my Indi, fantastic.
Now we are considering the following:
2.7l with 53k miles on it + IMS update + Clutch for 11k
or
2.7l > 3.4l conversion with 8k miles on it
The remaining questions are:
What does it take to marry a 3.4l (M97.21) from a 2008, with a 5-speed plus any extra's (exhaust, dme/ecu)?
Remember I have an 05' 987
Has anyone does this successfully?
09-02-2012, 04:35 PM
#25
Sounds like this mechanic has already dragged you over the coals. This "certified" (which, BTW means he pays LN to be on the "certified" list) mechanic should have known rule #1 from LN eng, - any engine that has already suffered an IMS failure is NOT a candidate for IMS retrofit, because of all the misc metal particles floating around in the engine.
Maybe you just have enough cash floating about to not care about the $1300.00 or whatever the initial stroking of the IMS cost?
Good luck dealing with this "IMS expert".
