High mileage, original IMS bearing, engine survival question.

Hello fellow 996 owners! I bought a 2003 C4S on BAT in May 2024, that the seller said might have early bore-scoring, for $20k. https://bringatrailer.com/listing/20...a-4s-coupe-27/ It "could be" super early bore-scoring, or just 150K mi of cylinder wear (I think the latter, and why I decided to buy it) I don't plan on driving it much (1-2K miles/year, it is just a toy) and I don't track it. I don't want to rebuild the engine, but could if had to. Considering an IMS change (maybe) as I think it is still on the original (single row?) bearing, but the sump/filter was clean at the first oil change, and the Blackstone report is good, so for now, I am in the "monitoring" phase. I have lowered the engine a bit (to change #4 plug, left cam sensor and aft motor mounts), and could do it again. Here is my question. After hearing about the hydrolock damage caused by a failed AOS, I am considering the UAOS from @Porschetech3 (from what I hear, a failed AOS gives no warning...) I know the AOS is difficult to access, so do you think I can/ need to put in the UAOS? Have you done it? Is it a reasonable job? (I did rebuild, myself, my 2.7 engine 20 years ago, and just had it out to change the high pressure fuel lines, so know a little.) Obviously I would like to prevent ANY catastrophic engine failure... Thanks, Paul

I think it�ll be a walk in the park for you, given your experience. I would suggest watching some videos to see what�s involved, and brainstorm what additional parts you�ll want to replace �while you�re in there�, such as: throttle body gasket, intake manifold gaskets, fuel injectors, starter y-cable, oil cooler seals, vacuum line elbows, etc. I siphoned a lot of powersteering fluid from the reservoir during this job, and filled it up with fresh fluid too. I also highly suggest getting the �track drain� option for the UAOS. And also to get yourself a smoke machine so that you can test for any vacuum leaks after you button everything up. I also removed my decklid from the car for my UAOS install. It allowed me to reach deep into the engine bay because my head was no longer obstructed by the decklid. I used one of these during the job and found it really helpful. Get yourself one of these if you haven�t already got one. Amazon Amazon

THANK YOU! That is what I hoped someone (with experience) would say! Paul I couldn't get the link to work, but I think it is this: TEKTON 1/4 Inch Drive x 10 mm 6-Point Universal Joint Socket | SHD08110 Thanks!

Yeah, that�s the tool I intended to link. Sorry about that.

Hi Paul, I would for sure put the UAOS System on it ...and also the Optional high mileage/Extreme Track Duty Auto Drain ... It is not just for Track Driven cars, but for high mileage cars as well to get the most performance and mileage out of them... Since there is a question about the valve seat on #3 , I also would suggest a Compression Test and if that is good, a Blow-by Test just to see what you got ... If these test prove average for a 150K miles engine I would just drive and enjoy !! ( the UAOS System can always be transferred to a new engine ...) .. Cheers !! Skip

I'll be the first to say that ims bearing replacement , even if it has a single row, given the engine already has bore scoring, might not be the best use of money. If you do go with an IMS Solution, then you could always reuse that on the rebuild, when it comes to that point. I'd focus on doing whatever you can to extend the life of your engine. Although you are beyond prevention, the same steps we recommend should be followed as that will buy you the most time, especially considering that you do not intend to drive the car that much. https://lnengineering.com/products/w...e-scoring.html

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Since I also have a high mileage (245K+ miles) 2003 C4S with original IMS bearing from the factory, I would say that one of the worst decisions you can make is to barely drive the car. My luck has been good, but if I had it to do over again I would have definitely swapped out the IMS for the LN solution when I first bought it 10 years ago. There is some great knowledge base and insight to be found on this forum on these fantastic cars.

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Congrats on the OG factory IMS and still going after 10 years

With high miles, you may consider using a different oil and more often changes. I recco that you listen/look at the video Slackker put on RL and Brandon Clarks thoughts. This one: 📺 Watch the full episode on YouTube: Ask Brandon Ep. 3 – The #1 Cause of Porsche Engine Failure (And How to Prevent It) I am switching to DI50, already have DI40. I don't do many miles, so that cost is also fairly low. I imagine it is hard to get to 3000 miles on an island! Also sent DM to you. YMMV

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Thank you Charles, I really appreciate how much first hand information all THE EXPERTS (you know who you are) give to us members here on RennList. Having experts with your level of knowledge and expertise reply to postings here on RL is unbelievable! As a contrast, I am trying to save my friends mom's 2011 BMW 128i. It wouldn't light up the instruments or crank, and had a few CAS "wake up" codes (Greek to me). But many other things worked... I posted a question on a BMW owners forum. I got responses like "change the battery", "charge the key remote battery" and other (neophyte) comments. None were useful. It turns out the depleting battery damaged the CAS module, and with a professional re-code (TheECU Pro) it worked fine. Back to Porsches... The sale listing for my C4S (from the seller's pre-sale inspection) said it has bore scoring, but I think the pictures show a 150k mi of driving... (no galling, yet). I have only done one oil change (just after I bought it, because I wanted to look in the sump) The oil analysis report didn't indicate any adverse conditions. I used LiquiMoly 5W-40 and a bottle of CeraTec 3721 for that oil change, and it has been just over a year now, but only about 2000 miles. Time to do it again? (BTW, who made up the 12 month rule for these cars? Why not 6 or 18 or 24?? It IS synthetic oil... The whole point of synthetic oil is less oxidation, right?) I know the engine could last another 100k mi (@cboxell is an example) or it could D-chunk, or have the IMS disintegrate the next time I drive it... but I don't think either is going to happen with diligent monitoring (but spinning the main bearings?? see video above... I don't think there is anyway to detect that before it happens...) I hope the former, because I don't love this car enough to do a pre-emptive rebuild (with no? symptoms) right now... Paul

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Paul, tough to tell if you are joking around or serious. Looks to me like you are begging your engine to fail so you can get a rebuild.

I have 155K plus on my original IMS (that I'm aware of) in my 02 Cabrio. I drive it daily and have put ~30k on since I bought it last May. IMS replacement is the plan for this fall. I actually did the AOS twice unfortunately... I wanted to do the UAOS when it went out the first time, but it was unavaible at the time and I didn't want to be out of commission for 2 weeks. So I put a stock AOS in, and then re-did it again when it went out again about 20k miles later... I now have the UAOS with the track drain. The job in itself is not hard. There are 2 bolts that are difficult to reach, but the swivel socket will help. As will a mirror to get a visual on the bolts. lots of pateince and ibuprofen as you'll be waist deep in the engine bay for a bit... I think the UAOS is totally worth it if you can plan to do it from day one.