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YOUR RESEARCHM96 engine replacement details
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most reliable of the factory bearings
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Reported cause
The larger bearing found in MY06-08 engines has the same load capacity as the early dual row, which have proven to be the most reliable of the factory bearings.
Leading evidence: 'most reliable of the factory bearings' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'most reliable of the factory bearings' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check checks out ok' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Fill with coolant, bled system, cleared all faults present &
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Performed · outcome unconfirmed
Removed engine/transmission assembly, unflaged & flanged, reinstalled engine/transmission, filled with coolant, bled system, cleared all faults present & test drove.
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Suggestion
You or your indy can drop the trans to take a look at the bearing as well as check the clutch and flywheel for wear at that time.
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Suggestion
You can check with LN to find out if there is a way to replace the "newer" factory IMSB.
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most reliable of the factory bearings
No successful repair reported for this finding.
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Reported cause
The larger bearing found in MY06-08 engines has the same load capacity as the early dual row, which have proven to be the most reliable of the factory bearings.
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Hi,
I have a 1999 Carrera 996 that had the engine replaced in July 2010. The engine number is M96 / 01AT66X67414. How do I determine what IMS bearing is in the replacement engine and the probability of failure.
Regards, David
I think there are some others that know a lot more about this than I do. But when I was looking for a car, I did come across one or two with a replacement engine & did some research. If yours was replaced in 2010, it most likely has the more robust 997 style bearing. However, it's possible that particular engine was older and had been sitting on the shelf for a while. If so, It might have the less robust 996.2 single row bearing.
Short story - To be totally sure, you would probably need to talk to a dealer and give them the serial number. Maybe they could give you the build date on the engine and an opinion on the style of IMSB in it.
OP - Best info I can supply is your engine serno is 1,000 “AT” rebuilds into the period when the new, unserviceable bearing was used. So 99.9% sure that’s what you have.
Use the example below to decipher your code:
The engine number M96/03AT665 68531 translates to...
M96/03 = 3.6L motor
AT = denotes factory replacement engine
6 = 6 Cylinders
6 = Natural Aspirating Motor
5 = date of manufacture = 2005
68531 = actual serial number
911 CARRERA M96.01 1998 W 66W 00501>60000 6ZYL/3,4L /220 KW /300 hp
911 CARRERA M96.01 1999 X 66X 00501>60000 6ZYL/3,4L /220 KW /300 hp
@daviddbohn
- look for the casting stamp in this post on your own car:
https://rennlist.com/forums/996-foru...ing-stamp.html
I explain how to decode the stamp in post #2, this will tell you the day that your block was made.
What this does not tell you
is what day your engine was assembled, hence, it will not tell you which IMSB is inside your car. It will be a clue, however, if the date falls well within a specific range. Say for example, if the block were cast in 2008 we can pretty safely assume it has the updated single row bearing that cannot be pulled.
So from my engine serial number, I must have an early remanufactured engine, my guess would be sometime early 2004 or even 2003 with a 5204 or 6204 IMS bearing.
Serial number on my engine is
M96/04AT66Y65546, so unfortunately for me number 65546 is 980 away from the earliest example you've seen with the M97 style 6305 bearing.
FYI my 996 that I previously owned had engine serial number M96/01AT66X67023 which I confirmed had the larger 6305 bearing.
I'm dusting off an old thread here, in hopes of clarifying....
So if I'm looking at an C2 with an AT factory rebuild engine, I want one BEFORE the serial no 66526? Am I interpreting this correctly?
Just trying to sort all of this out....
To sum it up:
Before gets you one that you can replace with a number of different aftermarket solutions with varying maintenance schedules.
After gets you one with a very low failure rate that you're stuck with. However, you can remove the seal with your next RMS/clutch job. To my knowledge, there are no reported failures of the large IMS after the seal has been removed.
It's personal choice, but I'd prefer the latter since it gives you more time to schedule it with transmission out maintenance without worrying about it blowing up in the meantime.
FWIW, in looking into "AT" engines 2 years back I found mentions of numerous AT serial numbered engines before 66526 as having the larger, non-serviceable, more reliable IMS bearing...so I'm pretty certain there is no exact "before this number, this bearing" reference
Ref here in forum for 65131
having the larger bearing, which is the earliest I have found.
https://rennlist.com/forums/996-foru...nt-engine.html
scroll down to bottom
Hey, that's a tremendous help!
That's huge - the car I'm looking at is AT 66247. MAYBE - just maybe - it has the larger bearing. That's a big push in the right direction for my peace of mind!
Does that seem reasonable? Am I interpreting the data correctly?
From my POV, I think it's a good assumption that 66247 has the larger IMS bearing, which I'd consider a good thing.
Earlier #'s
M96/03AT66565897,
M96/03AT66565812,
M96/03AT66565745,
M96/03AT66565160,
M96/03AT66565131 are all said to have that larger bearing as well.
Hope what can be checked checks out OK.
I am looking at a 2003 C2 tip cab's service history and had the same question (
How do I determine what IMS bearing is in the replacement engine and the probability of failure?
). There is an invoice from 2010 from a Porsche dealership when the car had 16,563 miles on it. Job #1 reads, "Customer states that the car was smoking and a loud knock was heard on re-start. Intermediate shaft broken, shavings throughout engine. See attached warranty assistance request for authorization. Removed engine/transmission assembly, unflaged & flanged, reinstalled engine/transmission, filled with coolant, bled system, cleared all faults present & test drove.
Old #66321022
New #66568799"
Parts: 996-100-995-BX .6L 05 996 CARRE
I have no idea what unflaged & flanged means. The part number is for a replacement engine. Actual new engine serial number is 68799 and it was built in 2005. Given the information above, I am comfortable believing that this car has the unserviceable, large single-row 997/
M97 style 6305 bearing and that it won't blow up.
I suppose the purpose of this post is documentation for myself that I went through this exercise lol.
During that era Porsche was replacing engines witg new ones that had the "new bearing". Usually it was due to not passing the "go-no-go" test. But some did fail resulting in an engine replacement as well. Its been said to pull of the rubber seal to allow oil to better flow over the bearings. You can check with LN to find out if there is a way to replace the "newer" factory IMSB. I cant remember if they have a procedure or not.
You or your indy can drop the trans to take a look at the bearing as well as check the clutch and flywheel for wear at that time.
No need to loose any sleep. Enjoy the 996. Great car!
Thanks
@GC996
, I reached out to LN. Their response:
"The incidence of failure with a 2006-2008 M96 or M97 engine that have this larger IMS bearing is highly unlikely with estimates being about a 1% failure rate, if not less.
We advise those with manual gearboxes that when you have your clutch replaced, it's best to have the grease seal removed off the original bearing to allow engine oil to better lubricate it. At that time, you can reseal the IMS flange and have the rear main seal replaced as well. Tiptronic cars, not having any components that need servicing, should have the grease seal removed off the IMS bearing as soon as possible. Grease seal removal will greatly extend the original bearing life.
The larger bearing found in MY06-08 engines has the same load capacity as the early dual row, which have proven to be the most reliable of the factory bearings.
There is no need for a direct oil feed for the factory ims bearing as the bearing will be submerged in engine oil once you have the grease seal removed. Likewise, invasive procedures to allow you to extract the oversized bearing that compromise the integrity of and introduce contaminants into your engine are not needed and can actually lead to engine failures.
For more information about the 06-08 non-serviceable IMS bearing and recommended preventative maintenance for these models, please visit:
https://lnengineering.com/products/the-definitive-guide-and-faq-for-porsche-ims-bearings/my06-08-porsche-cayman-boxster-911-ims-bearing.html
"
This car is a Tiptronic (I edited my first post to include this). 16 years later isn't quite ASAP, but sounds like it should be okay based on the failure rate. The link he included gave info for this thread's original purpose about the serial numbers:
"Engine numbers up to M96/05 69507475 has the smaller IMS bearing and engine numbers from M96/05 69507476 has the larger revised bearing. Engine numbers up to M97/01 68509790 has the older IMS bearing and numbers from M97/01 68509791 has the larger revised bearing."
If anyone from LN reads this, thanks for the extremely useful and quick response.
Quick question popped into my head for future maintenance: Is the replacement engine fully dressed with brand new external components or do they strip the old components off the dead engine and bolt on to the new engine? Let's take the water pump for example, which LNE recommends is replaced every 4-6 years or 50-75k miles (composite impeller, do 160 deg t-stat as well). Is it brand new with the new engine or is it the old one from the original engine?
