My Mechanic: Some 996 C4S's don't need IMS fix. True?

I had my Mechanic crack open my 2004 C4S to do an IMS fix. They do a lot of Porsche work and have experience with this job. They told me that some C4S's from this year don't need the IMS job because they have a different layout that has no problems. He took a pic of my IMS which I have posted below. Is he right? If so does anyone have more information on this? I can't imagine a reason he would have to lie.

You have the smaller single row IMSB which is notorious for taking out the engine. Go for the LNE Solution and never look back. Based upon other people's input I have to change my opinion (which was all I was giving to start with). I also assumed that the 2004 model was what we were looking at. I did not consider that the engine might be a replacement engine. So I stand corrected on all counts.

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That's the 6305 "M97" large single-row bearing. You must have a reman "AT" engine in this car. That's the non-serviceable bearing. Plus, very few reports of failure. I'd leave it alone until the time comes to rebuild the engine.

b3freak your service recommendation aligns with what my Mechanic said. I'm still confused about the reman AT part. This car has a first owner who had it for most of its life and put around 30k miles on it. Then a seller bought it from him and I bought it from the seller. It's now sitting at around 40k. So are you saying it seems like either the seller or the original owner blew the motor (maybe because of the IMS?) and rebuilt it, or replaced it with a remanufactured one? Does the fact that its an AT motor give some idea of when this might have happened? Thanks for your help.

The only way to make sure is to take a picture of the engine number. If it has an AT in it, it is a replacement engine. Here is my original engine number

The 6305 large bearing was not introduced untill 2006 , that means that sometime after 2006 your engine was either (1) rebuilt using the updated IMS shaft and bearing or (2) replaced with a factory AT engine built after 2006 ( AT = factory replacement in German). If your engine serial number has "AT" in it, it is a factory replacement engine.

How can there be two competing opinions ... OP, what are you paying your mechanic for if you don't trust his judgment?

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My opinion is your car had a replacement engine under warranty as PorscheTech3 mentioned. It�s definitely the 6305 non-serviceable bearing because you can tell from the image- the size of the center bolt and they fact that the bearing is larger than the access port. That bearing is very robust with very little reports of failure. It this was the original engine, it would have the most problematic bearing - the 6204. Count your blessings and just drive the car and not worry about it.

Whether or not his IMS is OK, it seems silly to pay a mechanic to take apart the engine without doing the fix while you're there.

Thanks for the help everyone. I got down under the car to find that engine number. It's too tight and also looks to be under some paneling, though its hard to tell. I'm taking it to my friend's place, he has a lift. I'll post what I find. I wanted a second opinion from the community obviously and it looks like my mechanic was right, but I wonder why he didn't explain it this way to me, or check the engine number to tell me the full story. I initially did trust him, they seem really capable, get great reviews and work on all kinds of Porsche sports cars with a specialty in racing, though they do a lot of normal work too. Hes kind of an odd cat though. I also talked to a few Porsche guys who were very skeptical of what I was saying about the bearing not needing replacement. Things just weren't adding up so I posted. Also I was under the impression you cannot do any of the IMS fixes for this bearing. Is that correct? I definitely told him to do the fix if he could while he was in there but he said they can't do anything for this type of bearing even if I wanted to.

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Because you can�t extract that bearing without splitting the case. The 6305 is larger than the port on the case. I don�t even consider grinding/boring out the ims port an option.

This is the problem with the internet when trying to figure this stuff out. You only get bits and pieces at a time, with important "bits" often left out either because it's too inconvenient to type it out or it just gets glossed over. If you really want to figure out all the different iterations of IMSB's, when the were used/produced and why, you've got lots of reading to do. As for the mechanic not explaining things better, to them time is money, and who knows maybe he was having a bad day, or maybe he's just tired of explaining the IMSB to his customers. The bottom line is that you've gotten mostly correct information, but in a disjointed fashion that doesn't necessarily make sense. Unless you're willing to remove the engine split the crankcase and replace the existing bearing with the IMS Solution (basically a $5k bill unless you start doing "while you're in there" stuff, which could bump it up to $7k in a heartbeat), you're already doing as well as you can do...

I'm resurrecting this old thread because I never put a capstone on it. Engine code is: M96/03AT66565028. So you guys called it. Factory replacement engine. Would love to get the full story for what happened from the original owner.