LN Eng retrofit post mortem

Can someone direct me to data showing bearing wear and function versus miles after LN Eng retrofit installation? If your m96 has the 13mm IMS bearing nut you can inspect or replace your retrofit bearing (as is now being suggested) for ~$3000 per visit. Might as well do RMS while you are in there. On the other hand, if you are considering using the LN Eng hybrid bearing as part of your reman or >MY05 rebuild (22mm IMS bearing nut) you will want this data first as bearing inspection would be prohibitively expensive. Unless you are okay with R&I plus tear down every 40,000 miles.

What exactly are you looking for? I can't really grasp from your post what "data" you require. The elective 40K mile bearing swap has been recommended by LN for a substantial period of time now- it is nothing new.

I am looking for operational life data for the hybrid bearing. I would assume that before the retrofit went into production data was collected to calculate MTBF. It is my understanding that a sealed bearing was selected by Porsche because of inadequate oil supply to the IMS bearing area. I also understand that this sparse oiling was taken into account during the hybrid bearing selection process. Perhaps we have a mechanical engineer or SAE person who can comment on what tests, metrics and qualification processes are industry standard for critical bearing applications.

I carried out the majority of tests for LN on this and supplied the data to them. There was also no less than three bearing engineers involved with this. I have utilized the same hybrid bearing technology in EVERY ONE of my engines since the beginning of my engine program and have a 100% effectiveness rating with them. Prior to the IMS retrofit being possible this same bearing technology was used in the IMS Updates for completely torn down engines that we reconstructed. LN has the data that you desire, whether they feel that your request for it is worthy of release of is up to them. Remember, Porsche Engineers designed this bearing and the associated issues. Do all the calculations and tests that you want, the results of the IMSR are speaking for themselves. Many of them have more than 40K miles, I put over 30K on the very first IMSR ever carried out in one year alone. That engine is still going strong. Contact LN.

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Not sure I understand what data you're looking for. As somebody who has nothing to sell, to gain or to lose from anybody choosing to worry about the IMS bearing, let me also tell you that I'm driving an original bearing'ed 159k mile 996, which is my 3rd with over 90k miles (all on original bearings). Also replaced a "perfect" factory bearing for somebody else. Through my work with other shops, I've seen 3 failed 996 motors (i'm seeking them out, and it's been somewhat rare to find one), none of them were an IMS issue. Also from my experience, I'd recommend a car that had a factory re-man'd engine, since the most likely issues w/these cars will not be catastrophic, instead things like AOS, starter, alternator, hoses, etc. will need replacement over time, which are all updated and newer in the case of an updated motor.

Last year we saw more water pump related failures kill engines than the IMS... 13 cars in a row to be exact.. Today we just has an AOS failure kill one. The IMS is the most widely known mode of failure, but far from the only one.

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No wonder my wife thinks I am nuts for wanting a 996. Maybe I should consider a more reliable vehicle... like a Lotus Esprit or Lancia Scorpion At least parts are available for Porsche... good thing.

I thought AOS problem is noticeable and water pump doesn't suddenly fail? Therefore fixes can be done before either one or both can kill the engine?

You guys are worrying entirely too much, honestly. It's one of the most reliable platforms I've been around. Properly maintained, I haven't thought twice about driving mine cross country, doing time trials in them, and driving them back...

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My thoughts exactly.

The AOS can fail in at least two different ways.. One of these does NOT cause the engine to smoke. The diaphragm fails and creates a crankcase vacuum that can pull oil away from the oil pick up tube and create an oil starvation issue. This creates low oil volume and pressure which killed the #1 main bearing and #3 and #6 rod bearings of one engine that we just diagnosed yesterday. That engine never smoked when the AOS failed at all, it just would not idle. A few days after the AOS was found bad the engine gained a rod knock and then effectively died. We have seen this same trait many times over from this particular mode of AOS failure. I experienced this mode of failure from one of my own stock engines in a Boxster in 2009. The water pump failure isn't what kills the engine... Its the secondary damage from broken impeller blades that silently circulate in the cooling system until they find a passage in a cylinder head to obstruct. The 2000 and 2001 engines have the smallest capillaries in the heads and these failures occur to them in much greater numbers than any other engine. When this passage is obstructed a very small portion of the head gains a "hot spot" and then a crack occurs.. Since this area has coolant and oil passages near each other the crack intsersects them and creates intermix. This intermix creates foamy oil and this can easily kill every bearing within the engine and even the cylinders. These are a couple of ways how the simplest of failures can cost you a complete engine. The moral of the story is to ELECTIVELY change the water pump every 3 years (no matter the milage) and the AOS at the same time. Perhaps since we have been working with these engines and their failures longer than anyone we are exposed to the majority of them. Who knows, but it certainly is real under this roof and we have documented EVERY failure we have seen..

Jake, thanks for the clarifications. I honestly never heard of the AOS failure you described. It's good to know the symptom (not idling?). I'll keep in mind the 3 yr replacement cycle for both AOS and water pump.

An engine swap every year or so should prevent most of these problems. Sorry, I couldn't resist.

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Seriously, this is getting out of control.... why does it always seem to swing to the extreme, the hsyteria of the m96. These modes of failures can be found on every car, yes even Honda's. Though, much respect to Jake, Im not buying the AOS, oil starvation issue, just my opinion... These cars are 11 years old now, proper maintenance, and if you want some sleep... get an IMSR.... Its either you get use to the IMS, AOS, Water Pump or you dont... if you dont, get out of it or pay the man. These engines are stronger than you think....

j beede - You are going to town aren’t you!!! Just relax and enjoy the ride...

My car bought at 66K miles 4 years ago is one of the most reliable cars ever owned. I would buy the car with the dry engine over your #1 color combo. Example: I wanted black interior but settled for gray instead in a silver car.

The person who experienced the AOS failure was at sea level where vacuum is the highest. The AOS can easily created enough vacuum on the crankcase to effect the oil being picked up in the sump in some driving conditions. While under deceleration the manifold pressure is as high as possible. The situation can also very easily end up creating aerated oil, which has no film strength. We have seen this exact same thing occur many times, and like I said it happened to my own engine in 2009. Its the only mode of failure that I have ever directly experienced with my own Porsches. I could not agree more in SOME instances. Our old test car was unreal, from start ups in 10F temps that took the car to redline (immediately)until it boiled over to running it for 4 hours straight on the chassis dyno till the exhaust system got so hot that the bolts holding the exhaust flanges together popped in half. That engine is still alive. With proper preventive maintenance and a pro-active mindset the engines can live a super life and take tremendous abuse. Of course, just like with any engine, a hell of a lot of it is dependent upon luck.

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+1000

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After reading your post(s) I don't think 996's are the right car for you.

Among the other early warnings provided by the "Guardian" are AOS and water pump issues on the list ?

Everyone who is freaked out about a 996 needs to remember that most of us don't log into this board (or any other) and post, "Omigosh everyone, guess what happened to me today? I took the car to work then took my wife to dinner in it and it DIDN'T BLOW UP!!!" We usually only post here if there is a problem. So reading this board too much may lead you to believe that 996s suck and are completely unreliable. Keep in mind Porsche built a ton of these things and most of the owners don't even know about Rennlist, yet these cars continue to run on a daily basis. So take forums and the posts on them with a grain of salt. Sure there will be a risk since this is a car that is around 10 years old, but prepare yourself for the risk, be proactive with preventative maintenance and go out and enjoy yourself in your truly awesome vehicle. Remember life isn't worth living if you're not going to take some risk for satisfaction!

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+ 996

Hey Jake...can you answer a question for me? How does the Cup AOS differ from stock? It's over 10 times the price...I was just wondering how it's better than the stock unit. Looking at photos, it just looks larger...but there has to be more than that. Secondly, would the Cup AOS provide any more "long term" security over the stock AOS? (if indeed it is larger capacity) Or is it only advantageous in a true cup car? Sean

AOS Guardian? Is there a convenient line or some place we can tap a vacuum sensor into to monitor irregularities? Dunno, just thinking out loud...

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Will the IMS Guardian alert us of these failures too?

Guys, foor the last few days I have been in my office working on the paperwork side of the IMSG and have been by the computer for 14+ hours a day.. Thats not the case today, the rest of this week, or next week as I have a lot to get done in the lab before we close the entire week of the 4th for our summer shutdown. I'll pop in when I can, but I have actual work to do after I finish my Lunch..

What happened to the 5,000 miles in 5 days test drive that was to start on 6/20?

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The factory was slow getting the final sample to me, we just received it yesterday.. and my Wife has been sick, so I am not personally carrying out this test.

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Topaz and TRT, You may be right... but I still want a 996. ...j

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Good choice, see ya!

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I think your time will be better spent looking for a 996 than hand-wringing about possible problems. Every 911 series (with perhaps the exception of the 84-89) suffered from some form of potential engine nightmare, whether it was busted head studs, badly designed cam chain tensioners, exploding airboxes or that interesting 964 motor decision to not include a major gasket. Porsches have always been, and will always be, expensive to maintain and repair. Just because 996s have come down in price due to the 150,000 Porsche sold, they are going to be any different. In fact, simply because of the complex electronics of any modern performance car, they are probably going to be worse. Deal with it, or go buy a Honda.

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I assumed that "water cooled technical discussion area" implied that technical discussion (including requests for and review of data) was welcomed. I will take your advice and see if Charles is willing to assist me.