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Sometime in Late 2005, Porsche changed the IMS bearing from a single row to a duel row bearing design. This has proven to be far more robust than the flawed single row design found in all 996 cars and some early 2005 997 cars. Effected engine models are m96 & m97.
With the release of the 997.2 car in 2009, Porsche released the 91A Engine which eliminated the IMS bearing system all together.
Sometime in Late 2005, Porsche changed the IMS bearing from a single row to a duel row bearing design. This has proven to be far more robust than the flawed single row design found in all 996 cars and some early 2005 997 cars. Effected engine models are m96 & m97.
With the release of the 997.2 car in 2009, Porsche released the 91A Engine which eliminated the IMS bearing system all together.
Does that answer your question?
All true except the change was from a single row bearing to a LARGER ingle row bearing, not double row, which only existed on older ('99-'01) 996s.
For the most part, cars with build dates of Feb-Mar 2005. Mine is a 2005 997 C2 with a build date of 03/05 and it has the larger revised bearing. The build dates may not be 100% absolute but are a good starting point. Also check the VIN to see if included in the class action suit. There are many threads on this in this forum, scroll through the survey thread at the top of the 997 Forum for more info and links.
The only way to determine what bearing is in an '05 car is to pull the transmission and look at the bearing carrier nut - bigger nut = bigger bearing (larger late '05 - '08 is on the left)
With the larger bearing, you can't replace the bearing, but that's OK if you'll only be street driving the car. There is actually an advantage to the smaller bearing car, in that you can replace it with an oil fed setup like that used in the Mezger engines in the GT & Turbo cars, but you have to inspect the filter and oil pan during a PPI to make sure there isn't any ferrous debris from the bearing already starting to come apart and then you have to replace it. This type of bearing doesn't have rollers or ball bearings in it - it rotates on a film of oil.
The issue with tracking the larger bearing cars is that with the increased circumference of the bearing, the bearing surface speed actually exceeds the design parameters and can cause it to fail. The reason is that the IMS bearing Porsche installed is actually a sealed alternator bearing that was designed for the inner race to be stationary and the outer race to rotate, however, in this application on the Intermediate Shaft, it's the outer race that's stationary and the inner race that rotates. Increasing the size of the bearing from the M96 to M97 engines allows for the ***** and outer race to be a larger size and therefore a little more robust, but now has the bearing larger than the access hole, which is why the larger bearing cannot be removed and changed without a complete teardown of the lower end.
The second problem with all the IMS bearings is that it's a sealed bearing that sits in oil. As the bearing seals wear, they allow the engine oil to penetrate the seals and actually wash out the lubricating grease that was sealed into the bearing during manufacture. Enough fresh oil can't get past the seal to adequately lubricate the internals of the bearing and you end up spinning a bearing with insufficient lubrication, which causes it to overheat, swell, and fail. Anyone with a small bearing car should replace it - sooner rather than later. Anyone with a larger bearing car should pull the grease seal that is accessible once the bearing cap is removed, which will then allow adequate splash lubrication of the bearing internals from the motor oil it's sitting in. This is all that can be done to prolong the life of a larger bearing car unless you tear apart the motor.
As Hella-Buggin states, 2009 is the first year of the 9A1 DFI engine that eliminated the bearing, but these engines aren't immune to issues either.
My personal recommendation would be to buy an early 2005 with no evidence of bearing deterioration and replace the bearing with The IMS Solution. Buy a car with extensive service records that show it was cared for, from a warm weather climate or one that was not driven in the winter, which will reduce the chances of bore scoring. Do a thorough PPI including having cylinders #3 & #6 scoped, the oil pan dropped, along with the other normal stuff, and you should be good to go.
There is such a car for sale (if he actually decides to part with it) from member Para 82. It's a 2005 launch car where he's already done the bearing. It has Adaptive Seats and PCCB brakes and is price about $6,000 too low IMO. Here's the link - https://www.cargurus.com/Cars/l-Used...ting=169099391
"My personal recommendation would be to buy an early 2005 with no evidence of bearing deterioration and replace the bearing with The IMS Solution. Buy a car with extensive service records that show it was cared for, from a warm weather climate or one that was not driven in the winter, which will reduce the chances of bore scoring. Do a thorough PPI including having cylinders #3 & #6 scoped, the oil pan dropped, along with the other normal stuff, and you should be good to go"
There is a process by which you can remove the larger bearing during a clutch replacement just the same as the smaller bearing. Someone designed a jig that bolts up to the case halves and allows for the excess material to be line bored which then allows for the bearing to pass through the opening. Not sure about the metal debris removal during the milling process but overall it looked like a viable solution for 06-08 owners.
There is a process by which you can remove the larger bearing during a clutch replacement just the same as the smaller bearing. Someone designed a jig that bolts up to the case halves and allows for the excess material to be line bored which then allows for the bearing to pass through the opening. Not sure about the metal debris removal during the milling process but overall it looked like a viable solution for 06-08 owners.
I'm aware of that process, and it's a good point of information, but no way I'm going to trust that the exacting tolerances required can be achieved when externally mounting a machine and milling the case of my $25,000 motor in order to remove the IMS bearing when the street driven failure rate on the larger bearing is as low as it is.
Interesting point but I'm thinking the part of the case actually being machined has nothing to do with the bore where the bearing resides. The machining is only done to the section of case material that is "outside" of the bore. Really has no effect. The material is only there because as Porsche made the bearing larger they didn't want to retool and redesign the case half so in essence it became "incased". This puts much less emphasis on the accuracy of the process.
If it meant getting into the bore itself then no way and I would see your point regarding accuracy with rudimentary tools/techniques.
Also not saying I still don't have reservations about the method but I think we needed to understand with more detail what the method is...
Originally Posted by Petza914
I'm aware of that process, and it's a good point of information, but no way I'm going to trust that the exacting tolerances required can be achieved when externally mounting a machine and milling the case of my $25,000 motor in order to remove the IMS bearing when the street driven failure rate on the larger bearing is as low as it is.
Also not saying I still don't have reservations about the method but I think we needed to understand with more detail what the method is...
Yup, I'm always interested in more knowledge and valid new processes to resolve issues with these motors. It would be great if someone who had this process done would chime in on this thread about their experience with the boring and longevity of the motor afterwards.
During my M102 hands-on M96/M97 engine building class at FSI, it was brought up and dismissed as a bad idea.
03-10-2017, 02:45 AM
IMS question
