Do These Cylinder Walls Look Normal?

I recently replaced my engine with a freshly rebuild long block (the new engine appears to have already failed, but that's for another thread). I replaced my existing engine because I thought it was suffering from bore scoring. I had the classic ticking noise. Upon removing the engine, I decided to scope the cylinders just to see what they looked like. See attached images below. I don't see a ton of obvious scoring, but maybe I'm missing it? I do see what looks almost like cracks in the cylinder walls as well as areas where the oil is kind of smudged in a vertical line on the cylinder. What do you guys think? Signs of scoring? What are those crack - looking things? Does the oil residue look weird? I don't really know what I'm looking at here. Advice appreciated.

There is no �bore scoring� in your photos. There are plenty of threads here and other photos on the web or at FSI or LNE, or�.

Wished mine was like that ...

Yes, normal. Can't explain the squiggly lines, but it's not scoring. Change your oil every 5K mil or 6 months whichever comes first.

You don't say if you scoped from the bottom or top? Bottom is preferable as the skirt scores first. I'm guessing you're from the bottom due to the amount oil. Like others said no scoring. The lines, i think ive seen those before in some other posted images here, as far as i recall they aren't anything bad but maybe someone else can chime in. Did you find the source of the ticking?

Jagtem, out of curiosity, what m96 engine is it and whats the story on the long block failing? You peaked our curiosity. 👍

Just throwing it out there but could the squiggly line be the two flow fronts of molten alloy have come together and chilled solid inside the cast right there? Anyhow I wouldn't worry about it being a crack.

Here are the two

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Thanks for the info, everyone. The cylinders were scoped from the top with each piston at BDC. It's an early M96 from a 1999 car (M96.01?) I recently had a freshly rebuilt one shipped after waiting almost 9 months for it to be built/ delivered. Swapped out my tired engine (the one from the photos) and began break-in on the new motor. All seemed fine. Oil pressures and coolant temps were monitored constantly. At around 100 miles, I lost power when accelerating up a hill. Felt like a bad multiple misfire. Engine died. I re-started and struggled to get up the hill. Engine started sounding REALLY bad, and then I noticed an absolute plume of white smoke. Shut it down and flat-bedded home. Have not tried to restart since as I've been out of town since the failure. Engine still has full oil and coolant. The only thing I can think is a bad head gasket failure? Any ideas? I'm beyond disappointed and will be contacting the company regarding their one year warranty. Hopefully they will help make this right. I will withhold the company name until I get a resolution.

Oh that is bad. At this point, you should contact the rebuilder and ask them what they want you to do for troubleshooting if anything. It does not matter what the cause of the problem is, it is their problem. Loss of power, white smoke, likely intermix, I assume they want to see the engine sent back to them. Let's hope they make it right.

Internet lore says head gaskets do not fail on these engines .

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Jag, sorry about your engine problems. what does your engine builder have to say?

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Correct, unless someone forgets to do the final torque angle on the head bolts. :-) Seen this more than once.

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Thanks for the input, all. I just reached out to the engine builder today as I was out of town for about a week immediately after the failure. Hoping to get a response tomorrow. They do explicitly warranty their engines for 1 year, but I'm sure this is still going to be a giant PITA. When I received the engine, it was missing a water pump and thermostat housing, which were supposed to be included and pre-installed. They quickly arranged the parts to be shipped to me, but I'm wondering it this oversight may have been indicative of a general lack of attention-to-detail. Based on Charles' comment, maybe they got complacent about the final bolt torques. We shall see.

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It didn't occur to me before, but if the head gasket did blow, maybe they reused the head studs. If you pay close attention to what some of these rebuilders are actually changing out vs replacing during the rebuild, it's easy to see why they are charging less. It's important to read the fine print.

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Deadly sin number 1.

Just spoke to the engine builder. Based on what I told them, they're thinking it may be the AOS? I installed a brand new AOS when the engine went in. It was an aftermarket/ OEM quality unit from FCP Euro. Is a failure of the AOS even a possibility here? The engine is spewing white smoke, has lost almost all power, and sounds like the proverbial "bucket of bolts". I wouldn't think that an AOS failure would cause such an immediate and catastrophic failure, but I'm not sure? They've told me to verify that the smoke is coming from both tail pipes and to check for oil in the intake. Thoughts?

A new AOS can fail or be faulty. Someone on Rennlist, I think, had 3 failures. This is why most now recommend UAOS instead. Secondly, if the engine sounds like a bucket of bolts, that�s alarming. Is something else broken? I would be cautious of starting the car at this point. I would check the oil and filter for metal just in case.

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It could very well be the AOS..... The factory style AOS has been known to fail right out of the box, even the OEM Porsche ones....People have reported AOS failure as soon as it was installed or two failures in a year...ect.. All the Factory style AOS's have the Mann+Hummel cast number on them so I believe they are all made by Mann+ Hummel ( who don't even sell them to the public) .. Mann+ Hummel have factories all over the world but are based in Germany and I believe they make ALL current Porsche AOS's , and they are all junk unless they are modified using my Patented proceedure that makes them "Lifetime".. If the AOS fails excess oil will be drawn into the engine causing extreme smoke, causes lower octane that can cause "pinging" ( metalic sound like marbles) , and can even lock the engine ( Hydrolock), Hydrolock can cause bent or broken rods,and even cracked cylinders in extreme cases.. This is the amount of oil it takes to cause this damage...very little and won't show up "low oil level" Here is where the oil will lay sometimes untill you go up a hill or turn a curve Here is the bent rods from an AOS failure Here is what happens when you go up a hill or turn a curve when the AOS has failed Here shows multiple cylinders all fail at the same time from Hydrolock Here is the classic D-chunk caused by Hydrolock

Thanks for the info. Sounds like my next course of action should be to check for oil in the intake before I try starting the engine again.

Dang man that sucks, I feel for ya. Hopefully the builder is being helpful, I am sure it wasn�t cheap and this seems like it could still be on them.

Pulled the throttle body. Found oil in the intake. See attached photos. It seems like this could definitely be the problem. The issue manifested while I was accelerating up a hill, so that checks out as well. On the bright side, it looks like this was not the fault of the builder and they were able to diagnose the cause based on my brief description of the problem so I feel I can trust them moving forward. The downside is that my brand new engine may be grenaded due to a faulty brand new part. Unbelievable. On Monday I will try to clean out the intake and cylinders the best I can and try to rotate the engine by hand. I've been told by my builder to disconnect the AOS pipe to the intake and try to run the engine and burn off all the oil to see if the engine will run normally. Fingers crossed. Any other advice?

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I know it's no consolation, but what AOS was specifically used? I hate to say it but when replacing the AOS using a manometer to verify the crankcase vacuum is in spec probably should be a must. For a factory AOS, it should be between 4-6" of h2o.

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I got the whole kit from FCP Euro a while ago. The brand of the AOS itself is "Vaico". I hadn't heard of this brand, but I trust FCP Euro to supply decent quality parts. The messed up thing is I bought this AOS kit intending to install it on my old engine, but I ultimately decided to have a new engine built, so I just saved the kit to install with the new engine. Can you say more about testing the crankcase vacuum? Is there a link or DIY to learn more about this?

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Although I believe Vaico is not a Porsche OEM, they are an OEM supplier for other automakers and I would say is better than some others. FCP Euro like many other parts resellers don't necessarily choose what they sell. They use e-commerce feeds from one or more wholesale suppliers such as Worldpac, IMC/Parts Authority, or SSF Imported Auto Parts. I won't call out any specific brands here, but there are clearly some brands that make products that are of questionable quality and most independent shops know what brands/products to use and which ones to steer clear of. The use of a manometer to diagnose issues with Porsche engines I believe was first done by Tony Callas at Callas Rennsport. Although not a new idea, it was new to Porsches. Tony also works on BMWs and they use a manometer for diagnostics. His tool which is geared more towards shops as it includes a handful of adapters for most Porsche models includes reference values which are not published anywhere based on his own research. https://lnengineering.com/callas-ren...ment-tool.html

How to: https://rennlist.com/forums/996-foru...l#post18573373

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Hmm, might this "aos crankcase vacuum measurement tool" be the same as this crappy manometer without the "CR" pad print? But it comes with ten bucks worth of hose and a cap "on sale" for just $399. Gee, thank's forum sponsor!

With the amount of oil pooling in your intake I think you have found the cause of you issue.. Many engines have failed in this fashion and the cause was never found ( when it was actually the AOS that failed, but when engines fail , oil is expected to be everywhere so is not suspected as the cause) Rotate the engine by hand to see if it will go 2 full revolutions...IF it does then start it up and test the AOS with the manomitor... If it doesn't rotate , then pull the plugs and rotate by hand a few times, then rotate with starter to pump out the oil...Install clean spark plugs and start to test with manometer... Hoping for the best for you and hope you "dodged a bullet" and that your engine is OK !!

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If not choosing UAOS solution why would anyone choose some aftermarket AOS when genuine Porsche version is so cheap (relative to some other Porsche parts). I was holding some (don't remember the brand) aftermarket AOS and it really felt like 'el cheapo' component compared to genuine which is much sturdier (not saying that fully translates to internal quality).

Assuming the engine is OK, do yourself a favor and get the UAOS track version and put it on the car. Doesn't matter if you track it or not. The risks that it can help mitigate (hydralock, d-chunking, intermix, blowing smoke, etc) on the street and track and the benefits it brings will allow you to sleep at night and not worry about "if it's your aos failing again". Too many 996 owners don't take the limitations and fragility of the AOS seriously enough and instead want to save a couple of bucks so they put the same crappy part back in the car. Admittedly many 996 owners are new and just don't know any better. Keep that baby running strong! ​​​​​​

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People dont know what they dont know. If u hang out here then u know but the majority of owners only find this upgrade after a failure.

Keep in mind that the AOS failure is the cheap part. The AOS doesn't;t cost much money at all. The collateral damage from the AOS failing is the expensive part. The failure path is the very thing that makes the system work, and that is vacuum created by the intake manifold during engine operation. When the AOS fails a bridge is created between the crankcase oil supply and the intake manifold. It seems the people that I talk to have yet to understand how the AOS actually works. In this case they certainly can't understand how it creates collateral damages when it fails to keep the air and oil separated. Once I achieve their understanding of this, then we have to talk about what happens when you try to compress oil in a cylinder. I use a hydraulic cylinder in this discussion, and then they sometimes understand it.

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The Genuine Porsche AOS is cheap but the Genuine Motorsport AOS is not ( $1600 for 996.1 and $800 for 996.2 ) and it uses the same exact diaphragm and both are made by Mann+ Hummell .( UAOS uses a diaphragm twice as thick) The Motorsport AOS has a chamber twice the size of the standard AOS, while this helps keep oil from the intake it also means less is in thee Sump and contributes to oil starvation...Another example of an engineer not seeing the whole picture... UAOS diaphragm vs Porsche Porsche diaphragm UAOS diaphragm

Every six months?!!!

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What's every 6 months?

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Absolutely. In the days when TBN was the king in regard to grading oil life it made a big impact on these mandates. Now that oxidation values have taken this over it's even easier to see that time in service for the oil takes away from it just like mileage. The oil is in service whether the engine is operating or not. As soon as the oil bottle is opened exposure to the environment starts the oxidation process.

Update: I pulled the front plenum crossover tube to get better access inside the left and right side manifolds. Found massive oil pools in there as well. See attached photos. I went ahead and wiped out the oil and cleaned the inside of the manifolds as best as I can. Also pulled spark plugs. The plan for tomorrow is to spray a bit of fuel in the manifolds and rotate the engine by hand to wash/ pump out as much excess oil from the manifolds and cylinders as possible. Fingers crossed that when I get things cleaned up and back together that the engine will run. If it seems to run okay, I will absolutely just buy the UAOS kit and install it before driving the car again. I will admit to some level of ignorance with regard to the AOS issues on these motors. I had heard that they could be problematic but didn't realize just how catastrophic things could get. I just assumed that failure would lead to a bit of smoking, it's crazy to me that this brand new part could allow so much oil into the intake.

Question for the experts @Porschetech3 and @BRS-LN . How much of the d-chunking events that occur in the M96 are actually caused by aos failure?

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I would render an estimate of about 75% .. Before I retired from Porsche in 2016 from heart failure, I saw many engines replaced from this very fashon of failure......A lot of the engines that carry the "AT" replacement engines were from this...( moreso than IMSB failure).. Basic Factory Warranty 4years / 50k miles and CPO Warranty 2 more years / 100k miles ...when a car came in smoking heavily , making pinging noise ( marbles in a can), and then would not turn over after shut down, or lock-up while running. The Porsche " Hot LIne" was contacted and they would require a Replacement Engine ( AT) to be installed. They would not even Pay/Allow us to open the engine for damage assessment, or to allow clean up of the engine to see how well the engine would perform. Their reason was that the possibility of a slightly bent rod or a hairline crack that would not be readily apparent, would manifest at a later date, so thier decision was to elminate any posibilty by replaceng the engine... I almost lost my own engine in this fashion and the reason I invented the UAOS.. I know I will be accused of "fear mongering" when I say this but there are still people who think a 1%-3% chance of failure (catastrofic) is an acceptible risk...I say BS, the failure rate should be 0.003% for anything that can cause catastrofic failure when driven in a normal manor ..and I'm not saying the engine is "junk" on the contrary, I'm just trying to educate to the real world and wake people up that these things can be fixed/mitigated without even opening the engine if you are educated... I truly hope the OP's engine will survive this trama ( as mine did) and I can use his example to help educate the comunity...

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I'll just add that we don't see many engines with d-chunks any more. Most all are coming in because of cylinder bore scoring. I do believe that the blocks cast with the Lokasil I process vs Lokasil II or III are more susceptible to d-chunking, although I have seen later blocks d-chunk too.

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Agree. Let�s just use rough numbers to say that 3% of 175,000 total 996s is still 5,000+ failures. I work in tech and have seen server memory failures up in the 0.5% range, and that is a huge pain for a lot of people. On the consumer side, this high of a failure rate would be totally unacceptable. When was the last time you or anyone on this forum had a bad memory device on their phone?

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5,000 failures is enough to keep the RL 996 forum busy with bad news.

Seems like an easy no-brainer to solve for the 4 modes of catastrophic failure on the M96. 1. AOS - UAOS 2. IMSB - LN Solution or Retro 3. Water Pump - New Oem water pump every 5-7 yrs. 4. Bore Scoring - Oil changes 2x a year with good oil, fresh fuel injectors, smart start-up procedures Pretty easy list to knock off.

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Right !! ...0.5% is "huge" ... I was a Top Troubleshooter for FoMoCo in the 90's when they went to the "Six Sigma" Program that called for a 0.00034% failure rate....it made a big difference.. Yes and enough to keep the bad info flowing when the other 170k people claim it is all "overblown"..lol

Update; Here's what I did: 1. Removed throttle body and front plenum crossover pipe to wipe out pools of oil in the left and right side manifolds. 2. Removed and cleaned spark plugs 3. With plugs out, squirted some fuel down each of the intake runners and into each cylinder 4. Rotated engine by hand with spark plugs out to help flush fuel through the intakes ports and cylinders. The engine rotated easily by hand. 5. Reinstalled plugs and throttle body, but kept the AOS plastic hose to the plenum disconnected. Plugged AOS port on the crossover tube/plenum. 6. Pulled fuel pump fuse and ran starter motor for several seconds. Again, engine turned over fine. 7. Reinstalled fuel pump fuse, crossed fingers and started engine. I ran the engine at around idle for about 30 minutes to try to burn off all the oil. The engine smoked heavily from both tail pipes as well as from the disconnected AOS plastic hose. Also removed the oil filler cap and got smoke from there too. The engine seems to idle okay, but it's definitely misfiring. Got codes for random/multiple misfires as well as cyl. 4 and cyl. 6 misfires. After about 30 minutes, the smoke was definitely reduced, but still smoking primarily from the left hand tail pipe (the one that gets exhaust from cylinders 4,5,6. Also still smoking from the AOS plastic hose. I know that a little bit of oil can generate alot of smoke, but I'm concerned that after 30 minutes I was still getting smoke from the left side tail pipe. Is there any other way that additional oil could be entering the intake? Remember, I've got the AOS plastic hose disconnected and that is currently venting smoke to the atmosphere. Do I just need to run this thing for longer? Regarding the misfires on 4 and 6.... Could this be a result of having the AOS disconnected from the plenum? Or could this be the result of slightly bent rods? Maybe fouled plugs? Would a compression test tell me if I've got bent rods? The engine actually sounds better. It's still a little rough, but definitely doesn't sound like the bucket of bolts it did before. I'm hoping the roughness is the result of the misfires and not something deeper. Any additional tests/ checks I can do to definitively diagnose this thing? Thanks.

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Looks like the cayenne 955/957 AOS diaphram. Or very similar.

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If the disconnected AOS hose goes to the intake that is a huge vacuum leak. You should plug the hole in the intake. The only way I know to find a bent rod is to measure distance from TDC to some fixed reference in the head, or take the engine apart. Even with a slightly bent rod the engine should run OK and make decent power. Perhaps a leakdown test at BDC might show if there are cracks in the cylinder walls. Borescope might work better. I would think that any residual oil in the intake would be gone within a couple minutes. Smoking at the exhaust after 30 minutes is not a good sign.

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It should look similar, Mann+Hummell is the Big Kahuna of OEM intake systems. They make numerous intake systems for many OEM manufactureres like Porsche, Vw, Audi, BMW, Mercedees ect....Most of the stuff they make goes straight to the OEM manuafacturers, they don't sell anything to the public except through Mann Filters... It's a good sign that you don't have any bad noise coming from the engine after the "Trama", but you are still a long way from declaring "survivour" .... The engine will smoke for 3-4 days up to a week getting less and less and only smoke after the temp has reached a higher level than previous as it burns away half-baked oil half way down the exhaust system... Depending on the mileage of your Cats and 02 Sensors, you may find the excess oil has killed them and start getting codes for Cats and 02 Sensors.. I would run Compression Test , Leak down Test, and especially Blow-by Test to try to gauge the health of the engine. I don't suppose you got any of these tests after the engine rebuild for a baseline?? The engine will not run smoothly with a failed AOS ( air leak) or if the crankcase vent is plugged off ( too rich) ..so that has to be corrected before you can expect the engine to be perfectly smooth... Like theperf said, even after all these testes are passed, and miles are ran with no smoke, and Cats and 02 Sensors have either survived or been condemed, and even if the engine is running smoothly, there is no way to know if a rod is slightly bent from the "trama" ... only time will tell ( or a complete teardown/inspect) .... But I am pulling for your engine to be a survivor !!! and hope the Porsche Gods smile on you !!

Update: After speaking with the engine builder, I am going to install a new AOS, new spark plugs, and new O2 sensors and gingerly run the car. In preparation for this, I am beginning to remove components from the engine for engine removal. I pulled the throttle body to inspect the inside of the plenum again. I was dismayed to find a fine coat of oil on the inside of the plenum/manifold. I had wiped the pools of oil from the plenum prior to running the car for about 30 minutes with the AOS plastic tube disconnected. My question: is there any other possible way for oil to be making it into the intake or is this just maybe residual oil from the back of the plenum, intake runners which I couldn't reach to clean? Perhaps the vacuum of running the engine re-distributed the small amount of oil which I couldn't clean. Also, I removed the mufflers and found thick oil dripping from the catalytic converter pipes. Obviously the cats will be coated with oil. Is there a safe way to clean/ flush the cats off the car? Can I just flush with some soapy water or brake clean? I will be replacing the O2 sensors as well. Thanks.

UAOS

Well, maybe scratch everything I just said. As I was preparing for engine removal, I decided to do a compression test. Cylinders 4 and 6 (the ones I'm having misfires on) have almost no compression. They read 10-20 psi versus the other cylinders reading 165-180 psi. Now I'm at a loss. Is this indicative of bent rods, even though I'm able to easily turn the engine by hand? I put a borescope in the bad cylinders to have a look. To bring this thread back full-circle.... see attached photos. Does this look like scoring? This engine has less than 100 miles on it. You can see the cross-hatching is still visible in some areas, but others look scored. How would a bad AOS lead to this? Is this from bent rods possibly? Cylinder 6:

Cylinder 4:

Leakdown test will tell you where the compression is going. Could be a bent valve, broken ring, cracked head, cracked cylinder.

So sorry it will not be a survivor... Those cylinders look terrible !!! ( and look like cast iron) Send me your old AOS, I have a special bench test proceedure to test them..... Chicken or the Egg came first....can be deduced on an engine from forensic evidence.. If the AOS" proves" to have failed , it can cause bent rods as shown in examples and the damage that insued.. If the cylinders failed first from (....not speaking to this at this time ) ... then the excessive blow-by would overwhelm any AOS and fill the intake with oil... Evidence needed to form a diagnosis....1.AOS test....2..rod straightness test...

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Yeah seem like maybe steel sleeved? Bummer, sorry it ended this way�.

Jagtem sorry for your problems. Curious also ,if A O S actually failed.

Oh man....

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Thanks for all the feedback you've been providing. If you're serious, then I possibly will take you up on that offer to test the AOS, unless there is a simple way for me to do it at home? Likewise for testing rod straightness... any foolproof method for doing this without tearing down engine? I will have another conversation with the engine builder tomorrow in light of this new evidence. Yes, steel sleeved. Supposedly designed to eliminate the possibility of bore scoring in the future...

Well, steel sleeved can probably be rehoned so that's something. Given those marks there are probably broken rings or pistons. It's pretty obvious that head has to come off to figure out what is bent/broken. When that is apart use a dial indicator to measure how close the piston gets to the block deck and compare the 3 cylinders. If #4 and #6 are more than a couple thou different than #5 I would assume the rods are bent.

And the plot just got thicker and thicker...

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I'm absolutely serious, send the old AOS to UAOS C/O Skip 2101 Ridgebrook Rd. Fultondale Al. 35068 I'll test it using my bench test method. The flow regulator works in a unique way using 4 pressures ( crankcase pressure, intake pressure, spring pressure, and atmospheric pressure) in two opposite directions open/close to regulate the amount of flow for all load conditions...Most don't understand how it all interacts and is the reason it remained unimproved for 20 years untill I almost lost my engine due to the frail diaphragm membrane. Then I was determined to redesign the system.. Since disassembly of the engine is now shown inevitable, it is easier to remove the rods and lay on a flat surface to determine the straightness, than to measure in situ.. You can measure piston to valve clearance in situ the same way it is done when designing a high lift Cam, to ensure a 0.070 min clearance at all degrees using dial indicators and degree wheel, but that takes many hours to get precision measurements...less time is spent to just tear down the engine.... Yes I have designed my own Camshafts back in the 80's, you can't set new world records by using a Cam that has already been designed and in use...

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Skip beat me to it yet again. If the cylinders failed first then the loss of ring seal could certainly overwhelm the AOS. I'm wondering if they reused the stock pistons and did not remove the ferrous coating off the skirts or if they set the bore size to the nominal 96.00mm which would have been too tight for the iron liner. I've seen this time and time again when blocks come to us that were done by someone else with steel sleeves that the components are mismatched and clearances aren't right. This damage could have also been caused by improper honing of the bores, poor cleaning of the parts before assembly, or purely an assembly error (improperly gapped piston rings, broken rings from not using a tapered sleeve ring compressor, piston ring installed upside down, etc.). I'll throw out there that I've seen also engines fail from the scavenge pumps being installed upside down which would cause other oiling related issues. Regardless, I'd wager to say the AOS was not the cause of the failure and is a symptom of a larger problem with the engine.

@Jagtem Quick question -- why are the pictures in the first post from stock Lokasil bores while the last pics you posted are clearly honed? Did the builder only steel sleeve one cylinder?

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The first pictures are from his old engine... then his new 100 mile engine are the recent set... I agree with everything you said Charles, I was biting my tongue , a habit I aquired from doing Expert Witness work in last few years...I see some very interesting car cases......

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^Correct. Thanks again for everyone's input. At this stage I've got half a mind to just scavenge the new components off the new engine (timing tensioners, water pump, etc.) and install them on my old engine and put it back in the car.... The only problem is all the exhaust manifold bolts snapped off in the old engine, but I imagine I could get a machine shop to remove them/ re-tap the threads. Last night I took some more detailed photos of my old engine's cylinders. I'll attach them below. Based on these photos, it looks like my old cylinders are now in much better shape than the ones on my "new" engine. Would I be crazy to just install my old engine? "Old" engine cylinder 1: Old cylinder 2:

Old cylinder 3: Old cylinder 4: Old cylinder 5: Old cylinder 6:

I know it's impossible to tell from just photos, but would it be advisable to just run this engine? I only replaced it because I suspected bore scoring based on the infamous "ticking" sound. But the cylinders appear okay. Maybe I just clean it up, get a leak down test (possible while out of the car?), throw a new IMSB on it and run? Engine has 130k on it and ran strong but was beginning to leak and smoke around corners (the reason I bought the AOS kit in the first place). Argh. This is a nightmare. Thanks for everyone's help.

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If you still have the original engine, it might be worth considering putting it back into the car. Yes, you should be able to do a leakdown test. You'll probably need to squirt some oil in each bore and turn the engine over before carrying out the leakdown test on each cylinder. If you still have a flywheel on it, you might be able to do a compression test as well by just throwing a starter on it, but the engine will have to be secured as it's going to be squirrely out of the car :-) Obviously not as good as a running compression test, but it's better than nothing. If you do put it back in, on top of a new AOS I'd advise running a tad thicker of an oil, specifically Driven FR50 due to the extra moly that is in the Driven oils as we know this helps protect the cylinder bores best. Also don't rob any of the components off the "rebuilt" engine that has failed on you. You don't want to inadvertently contaminate the old engine with a component that has FOD from the failure. Although you can't do it easily with the engine out of the car, you could also pressurize each cylinder with compressed air and put a pressure gauge on the coolant expansion tank (or a rubber glove works too) to see if you end up pressurizing the cooling system in the process. I saw a Porsche tech at the dealership do this years ago to check for cracked cylinders in a 996. Likewise with a filled cooling system, you can also pressurize the cooling system and look in each cylinder for coolant intrusion into the cylinders or the crankcase (with the sump removed of course).

^ Good info. Thanks, Charles. I got the engine out today. Drained oil didn't look too bad, but It seemed like there was maybe a bit of oil in the coolant when I drained that, really small amount though. Possibly being overly sensitive. There WAS, however, lots of metal shavings in the oil filter. See attached pictures below. At this point, the engine builder is still adamant that the fault couldn't be theirs. They are still pointing the finger at the AOS. Their theory is that the AOS failed causing the engine to hydro-lock on oil resulting in catastrophic bent rods and bore scoring and loss of compression on cylinders 4 and 6. The only odd thing is that cylinder 1 is also scored, but compression is still fine there. I will likely be taking up Porschetech3 on his offer to test the AOS. I'll send it to him on Monday. Once he makes a determination on the AOS, I'll consider my next moves.

This all really stinks, I feel for you. It really upsets me when these things happen and engine builders instantly put their hands up and blame a part that wasn�t theirs and/or the owner. I have seen this countless times in my years in the car game with all engines and engine builders. Very rarely are they interested in helping the owner regardless of their own interests.

Quotes source post: 18608824

I have no problem going out on a limb to say that even if the AOS failed, that is not what caused the cylinder damage. That is an accumulation of wear that didn't happen overnight.

I have done a detailed bench test on the AOS from the new engine and it has not failed, this means the cylinders failed first at only 100 miles.. I would say the piston/cylinder clearance initially was not enough to account for the piston diameter growth when warm, or that the engine suddenly overheated causing the piston diameter to grow quickly to a larger diameter than the clearance provided and cause the extreme cylinder wear and galling.. The extreme wear and galling of the cylinders ( different from bore scoring) allowed way to much blow-by gasses to pass the cylinders and slightly pressurized the sump while flowing way too much air flow through the crankcase vent system, this pushed oil into the intake causing the smoke and possible hydro-lock. So even if the rods are bent from hydro-lock, it is the failed cylinders that caused this and not the AOS..... ( Although the UAOS would have kept it from smoking and kept oil out of the intake, it would not have saved this engine.... This engine failed due to cylinder/piston bore failure very quickly..) Once the piston/cylinder start to gall, the temperature shoots out of sight and can even seize/lock-up very quickly. I have seen it happen in a matter of seconds. If the engine didn't suddenly overheat, then the issue is just due to the initial clearance. It's all about the initial clearance and the piston growth. Pistons made from a 2618 Aluminum Alloy need more initial clearance than a piston made from a 4032 Aluminum Alloy, and either one of those will need more initial clearance if used in a Iron/Steel cylinder to keep it from galling... A 4032 Aluminum Alloy Piston in an Aluminum Nikasil cylinder ( like LN does) can be ran the tightest without galling...Tighter without galling means more power and less emissions... For further analysis, the initial cylinder clearance needs to be known and piston material type...

Quotes source post: 18632338

I'll just clarify a few points. We use 2618 alloy forged pistons as our liner material is best suited to run these pistons due to similar expansion rates and allows for tighter clearances. We typically do not use the 4032 alloy as you have to run them tighter in our cylinders, otherwise they'll be noisy when the engine is hot. We do not have any piston slap issues with the 2618 forgings when paired with Nickies.

Quotes source post: 18632338

Wow, one I think it was great of you to do such a detailed analysis, hopefully the OP can use this to try to get some resolution. Not trying to rub salt into an open wound at all, but I think this is a great example of why it is critical that you select someone who is well proven when rebuilding these engines. Sure they might cost more, but I would rather spend $30k and know I am getting something that is tried and true than gambling $18-20k and risking this type of outcome. Lastly in general it sucks to see these outcomes when engine builds fail, even ones with written warranties like this. The builder immediately points to some that isn�t their fault. I have seen this with all makes and models far more often than a builder stepping up to address this issue.

@ PorscheTech - Thanks alot for your detailed analysis and breakdown. I will be forwarding this information to the engine builder and will keep the thread updated with their response. I have so far withheld the this particular company's name pending a favorable resolution. We'll see what happens. Thanks again for all the insight, everybody.

I don�t know how warranty works with engines, but if there�s less than 5% failure rate, then a 5% premium for a warranty on the engine should make this a no-brainer. They should just send an engine, or if local, install a replacement.

So this was not an LNE repaired block, I assume? The last 996 I did, the block came back from LNE with perfect bores, new pistons, new rings. all I needed to do was to grind the rings to specs (14 thousandths) and all was good, The next one will also go to LNE.

Posting a long-overdue update to this saga. The engine went back to the builder and was torn down for inspection a couple of months ago. I also moved to Europe during this time, so I haven't exactly had a ton of time to deal with this situation. As a part of this process I ended up selling the car with the old/ bad engine for just $10k. Broke my heart to do it. Anyways, the engine builder is claiming no fault and saying that the catastrophic bore scoring/ compression loss must have been the result of rapid overheating. Here is the direct email quote: We finally have your engine apart and took it to our machine shop that does all of our sleeves, and piston fitment for each rebuild. We have a couple videos at the machine shop showing piston clearance which is correct: 0,06 on all cylinders. Only 3 cylinders got scored, if piston clearance would have been wrong, all of them would be the same. This led us to the conclusion that this engine must have been overheated. Some cylinders cooled more, some less because there must have been an air bubble in the cooling system. Pistons got swollen due to the temperature, it's visible in the video and pictures how they expanded under the heat. If clearance would have been wrong, the pistons would wear out in the middle first, the widest area. In this case, pistons expanded on the sides due to high heat, material expansion was on the sides because of the supports (explained in the video). Again, if the clearance is wrong, then the middle (widest) part gets worn out first. In this engine, the sides expanded first which indicates overheating. We've noticed you also installed a smaller crank shaft pulley, because you cut off a piece of the block. The smaller pulley changed the efficiency of the water pump, and added to the whole problem. All of those things cumulated adding to the overheat. Coolant system in these engines has to be bled correctly, because they're easy to overheat. When we install an engine we always start it for a while so as not to heat it up too much, then shut it off and add coolant on a cold engine. This procedure has to be repeated a few times for best coolant system bleeding. The temperature on your gauge will not show anything abnormal even though you might have an air bubble in the system. Engine could be too hot and gauge can show you a normal reading. I find this a little hard to swallow. I specifically purchased and utilized the AirLift vacuum coolant tool to do the initial coolant fill. I then of course kept a close eye on the coolant level and burped/ topped off while idling/ running with the coolant vent valve open. I also ran the car for about 100 miles while constantly watching the temp gauge like a hawk. During the moment of the actual engine failure, the gauge did not indicate that the coolant was overheating. Is it even possible that the engine could overheat so rapidly that it wouldn't even register on the temp gauge until it was too late? I would find this to be an incredible engineering oversight on Porsche's part if this were possible. At this point I no longer have the car, and I'm out over $12k for the engine. The builder refunded my $4k core charge when I sent the newly built / blown engine back for evaluation, but they're refusing to admit any fault or honor the 1 year warranty. Any thoughts on if their position has any merit? I've worked in automotive/ performance shops my whole life and I know that you can't warranty against incorrect use by the end user, but I took every precaution to make sure that I installed and broke in this engine correctly. Considering that I used the correct vacuum fill procedure and then burped the car while running it for 100 miles, I find it hard to believe that a small air bubble could cause this kind of destruction. What do we think?

I think u r getting screwed from every direction. Unfortunatetly there is not much u can do about it but tske the guy to court and that will cost u more. U can bluff by sending him papers and see if he will settle? Imho if the motor was built correctly with the correct procedures this wouid jot have happened.

Unfortunately the AOS has been known to fail very quickly,,, especially if you get one thats NOT a real Porsche one.

I think the engine failed and still, nobody really knows why. It doesn�t sound like it was your fault. It�s true that an engine can overheat and not show up on the gauge. The reason is because a water temperature sensor cannot detect heat if there�s no water circulation. I agree, engine designers should have considered putting another sensor somewhere else to protect against water pump failure or a complete loss of all fluid (although that would be pretty noticeable). I�m sorry this happened to you. This sucks.

Quotes source post: 18941739

We put overheat tabs on the exterior of the engine case's coolant passages. If the engine is overheated, the tab's center melts out. Many cylinder head and engine rebuilders use them for warranty purposes. An air pocket can certainly overheat the engine - we've seen this happen before, but using the lift tool should nearly eliminate the chance of this occurring. As far as the temperature gauge, on earlier 986/996 models the gauge responds very quickly, but by the time you get to the 997/987, the reading is dampened and delayed. By the time the temperature starts increasing on the dash, the engine is much hotter than it actually is reporting. I know I've personally seen a car with data show 180ish (the normal position) on the dash while the actual coolant temp is 225F.

Quotes source posts: 18940702, 18941739, 18941891

Wasn't an AOS failure. The unit was tested and ruled out as a culprit. Thanks for the info, guys. The only reason I don't think it was an air bubble (aside from me using the vacuum fill tool) is that I ran the car for around 100 miles before this incident occurred. I would think that an air bubble of that size would have made itself apparent much sooner than that, no? At this point it's just speculation and I appreciate everyone's input. I think I will at least try to get a partial refund from the builder. Ironically, there is a lawyer who reached out with interest in possibly buying the car when I had it listed for sale with the blown engine. I ended up selling the car elsewhere, but he's a Porsche guy and has offered to send a letter to the engine builder requesting that they honor their warranty. I'm sure it will cost me a few hundred bucks, but might be worth it if I can recover a few thousand in the end. If they don't play ball, I will be sure to post their company info here. It is a company that I'm sure many of us here have heard of as they've been offering budget M96 rebuild services for a long time.

Did the builder tear things down far enough to get a look at the bearings? I had an engine die at 70 miles due to a bearing failure which Jake attributes to the oil filter being pre-filled before the initial start-up. Debris made 3 of the cylinder walls and pistons look scored even with Nickies.

Quotes source post: 18962280

Can you elaborate more on how this would have damaged the engine? For me it is common practice to at least saturate the filter element during oil changes.

Quotes source post: 18962391

https://rennlist.com/forums/996-foru...l#post17094609

FWIW,, to back this up a bit,, I work in the IT industry, and a big part of my Job is ownership of some very large chiller plants, The chillers have Oil filters on them, and most all have a warning label to NOT pre-fill the filter or bearing damage will result.. Makes sense to me.. I haven't pre-filled a oil filter in years, then when Jake told me not to on the new engine I was like "makes sense to me"

Quotes source post: 18941891

So that's what those are !! Ha !!

Quotes source posts: 18962280, 18962391, 18962400, 17094609, 18963232

Interesting. I'm pretty sure I did pre-fill the oil filter, as I've always done that for regular oil changes. Didn't realize it wasn't advisable on this engine. But I have a hard time believing this would be the cause of catastrophic bore scoring?

Quotes source post: 18963812

https://rennlist.com/forums/996-foru...l#post16652578 That's why I asked if the builder sent you pics of the bearings. In my case damage to the #7 main bearing led to a spun #6 rod bearing. The rod bearing material caused enough damage to the cylinders, that LN recommended the block/Nickies be completely redone (which they kindly offered to cover).

I have never prefilled oil filters.... ever.

Quotes source posts: 18963843, 16652578, 18963922

Well... Now I know something new. The builder did not send any pictures of the bearigs and never even mentioned pre-filling of the oil filter as a potential culprit. They did however send me the following pictures of the bores/ pistons themselves. Nasty:

Part of the issue I see here is they reused the stock pistons. The pistons have an iron clad coating. You can't run that on an iron bore. That's a recipe for disaster. I wonder what they did for end gaps and for piston to cylinder clearance too. The reason I ask is that I see this all the time. I'd say at this point about 1/4 of all the blocks we are getting in have been steel sleeved.

Quotes source post: 18971915

No effing way? Who would do that on a rebuild? You buy new pistons, new rings, to go with the new bores....

Quotes source post: 18972983

They may have been new but should not have been the stock pistons according to cn's experience.

Quotes source post: 18973635

Considering the cost of new factory pistons, I highly doubt they put new ones in. :-) We see this all the time. People don't know what they don't know.

Quotes source post: 18971768

Those pistons look super dry

My guess is that between the iron clad skirt coat and incorrect piston to cylinder clearance, those two factors contributed to this failure. I don't think this was caused by pre-filling the oil filter (I'd expect the main and rod bearings to show damage if this was the case) nor from an air pocket in the cooling system.

I have a feeling the op is getting f'd in this one. I would deff trust cn's anyalysis over a builder that thinks iron sleeves r a good idea for these motors. I also find it hard to believe there is no "overheat" tab on one of the heads so the builder can prove it got hot. Not sure u could prove either theory and its probably what this builder is counting on. Be nice to know who did the work.

The engine builders with the best track records moved past using iron/steel liners in this engine a long time ago save for possibly Jarno at Werksmotor in Germany. It is a cheaper path but presents several challenges including considerations due to different thermal expansion rates and inferior heat transfer properties. It also has poor wear properties compared to Nikasil.

Quotes source post: 18971915

According to this post, " piston clearance ... 0,06 on all cylinders. " https://rennlist.com/forums/996-foru...l#post18939525

Quotes source posts: 18976155, 18939525

That's roughly what we run with a forged piston with our aluminum sleeves (varies on brand of piston, alloy, and cam skirt profile). I can't comment if that's appropriate for a steel cylinder, but with a JE Piston on an aircooled engine, you typically have to run .0015" to .002" more clearance with the same 2618 forged piston on a steel cylinder vs an aluminum one. Piston alloy also is a variable. A 4032 high silicon piston can run about .0005" less clearance than you would otherwise run with a 2618 forged piston. I am also curious where they measured that 0.06mm clearance as piston skirts are cammed and the gauge point can vary depending on the piston. Lastly, unless they match honed each cylinder to each piston, I highly doubt those used pistons all measured the same. Hell, even in new aftermarket sets we can see up to a .0005" variation between the smallest and largest pistons, so who is to say some of the bores were tight, especially if all those used pistons did not come out of the same engine.

Just based on random exposure to race setups. (not specifically any Porsche engine) Steel sleeves in a AL block with forged Pistons need about .008+ REALLY depends on teh piston builder. The pistons pictured look like a classic "stuck piston" from a motorcycle.. They needed plenty of clearance due to piston expansion. Going to lean or too rich was a fatal mistake ...

Op another thing to consider is the "break-in process" ...... During break-in the pistons will usually run much hotter than " after break-in is completed"... The pistons transfer their heat to the cylinders through the rings to the cylinder walls, when the engine is not yet broken-in, the rings are not sealing well to the cylinders and much less heat is transferred to the cylinder walls therefore the pistons will run much hotter ( and grow larger) during break-in with mostly oil splash/squirt to cool them... This is one reason the "break-in process" is so critical. Did you get a specific break-in regimen from the builder? What exactly was your break-in regimen??

Mine for comparison (Short version i had a specific list but this is off the top of my head.. ) was nothing over 3500 for the first five hundred miles on Breakin oil, dump the oil then nothing over 4500 for 1500 more miles (non synthetic) dump the oil then drive normal with no hard pulls to redline, for 1500 dump the oil again... switched to lubrimoly.. Drive it.. At this point, part of the tuning logging I was pulling 3 full power pulls to 7K in 3rd for each log to the tuner. Cut the filter each time (I have a LN solution) Check the magnetic drain plug. OVERNIGHT drain on each oil change nets almost another quart especially if you have the plug out and the Oil filter off.

Quotes source post: 18976379

The break-in regimen as provided by the engine builder was quite straight-forward, and I complied with it (until about 100 miles, when the engine popped): Break in period First recommended oil change is after first 1500 miles. After that every 4,000 miles. If these requirements are not met, warranty will be voided. Customer is also advised not to go over 4000 rpm's for the first 1500 miles. All parts inside the long block have to break in. Always use Mobil 1 5w30 synthetic oil formula or better. The only thing I changed was that I actually used Driven BR 5w-30 break in oil. Is it possible that using the break-in oil could have caused problems?

BR30 was a good choice for a break-in oil and certainly that did not cause the damage shown in 100 miles. Based on the information provided it seems that there was a problem with the rebuild itself. I am in full agreement that the break-in process is important but this engine suffered a massive amount of damage in just 100 miles. Looking at the pistons and cylinders it is so bad in such a short period of time that it reminds me of engines I have seen torn down where someone ran it with low oil pressure; that is an incredible amount of damage for just 100 miles. BR30 for 100 miles has nothing to do this IMHO.......

Quotes source post: 18995604

As long as the car wasn't tracked with BR30 in it, I don't see that causing a failure. In years past we have recommended BR30 for break in of street driven cars in colder climates, however BR40 would likely be a better choice, especially in hot climates.

Quotes source post: 18995544

Whatever engine builder recommends Mobil 1 let alone M1 5w30 isn't qualified to work on a lawnmower, let alone a Porsche!

Yes, agree normally you would run BR40 but since the engine builder states to "Always use Mobil 1 5w30 synthetic oil formula or better" possibly a 30 grade is deemed more appropriate by the builder due to their modified specifications. In this case it seems appropriate to follow what the builder said to do and all the specified procedures were followed for break in and otherwise as stated by the OP.....and considering how terrible the pistons and cylinders look in just 100 short miles this is surely something to do with the build. If the AirLift was used it is the best tool and there will be no pockets of air in the cooling system. That is especially critical on these cars due to the setup but it seems all the appropriate procedures were followed by the OP. There are a lot of places builders can go sideways in a rebuild if they don't know exactly 100% what they are doing. I am sorry this happened to the OP.

Quotes source post: 18995733

It is a valid point and a similar thought went through my head but I will give them the benefit of the doubt. Most people without a background or knowledge of chemistry don't understand even the most basic differences in oils, the technologies they use, etc. That being said if the engine can run a SAE 40 grade hot viscosity I would definitely choose that over the SAE 30 grade.

Quotes source posts: 18995731, 18995733, 18995756

These were my thoughts as well. I've always run LiquiMoly 5w40 as normal oil for other Porsches. I worked at PMNA for a few years, and remember some of the engine builders telling me that Mobil1 was garbage.

Mobil 1 is "garbage" in non-technical terms. The ubiquitous 0W-40 is effectively a SAE 30 grade straight out of the bottle (so I'm scared to even think about what their 5W-30 grade hot viscosity cSt is, terrible I'm sure) and has many other characteristics one could easily pick issue with (high Ca, etc). But let's also be fair; it is an inexpensive oil that you can buy at Walmart. It cannot be compared to more advanced technology like metallocene catalyst PAO technology as chemically it is different. Different production methods and technologies have different trade offs including expense. But in this case, even running M1 5W-30, this never should have happened to you in 100 miles if the engine was built properly.

Quotes source post: 18995956

Agreed.

Quotes source post: 18571062

Hi everyone! Just looked at this topic and found a similar "squiggly" line like on my engine... just for sure, is it really not crack but the squiggly line? I was sure this is not a problem, but my friend told me that these are definitely cracks and I am worrying now, although he has no knowledges about Porsche at all)) Picture of my lines is below:

Navarro is the real expert so hopefully he will opine. Also it is always helpful if you can post which engine and model year we are looking at. That being said the squiggly is nothing but the crack is concerning. It looks like it could be the beginning of D-chunk........

Quotes source post: 19083255

thats just a squigley line.

Quotes source post: 19083392

Yes, just a squiggly line.

*deleted*

I am an idiot. I was looking at yelcab's photo that was quoted. I thought it was two separate photos.

Quotes source post: 18995796

Hi Jag, I'm following this thread with a close interest. Have you had any more interactions with the engine builder? I am interested to know who it is at this point - I think that would be fair enough given the runaround you've been given. Hope you've had some luck with the lawyer.

Quotes source post: 19085756

The OP can speak for him/herself but I highly doubt it. When I bought my 996TT from a famous athlete who took a nosedive in life and made bad decisions he ruined my gearbox and I took him to court in what should have been a slam dunk case given the evidence I had. He showed up to court wearing flip flops and sweat pants, this kid is a real piece of work. Before I even could say a word the judge said he wanted to say a few words before we started... then proceeded to give this prelude telling me that he was disgusted with "rich people" like me that can afford this car and that he was very upset the local taxpayer money had been used to build a new track (I don't even live in this state much less pay taxes there). As if that had anything to do with me or my case. What the actual F. Anyway, without getting off on a tangent the reason I always tell people to go to Raby or LN or Hartech is because it doesn't make sense to go to anyone but the very best even if it is a little more expensive because once the money trades hands, it's gone baby gone. It doesn't matter how much evidence you have, the court system does not protect buyers in this regard in most situations. I fixed the gearbox better than it ever was and learned my lesson about dealing with people like this.

Quotes source posts: 18962400, 17094609

This is interesting. Lake posted saying you SHOULD pre-fill your filter as you get better oil pressure faster basically (but I don't understand the part where he is saying some people think oil is dirtier out of the bottle?). You Tube I see Jake says very clearly you should not pre-fill, even with oil changes. I wish he was still around..... I checked the shop manual just out of curiosity (not that everything in there is always right) and it does not say that the filter should be pre-filled. Also some cars including one that I own have the filter mounted on top of the engine. Even if I pre-filled, when I went to install it would dump oil all over my engine. I am a bit confused........

Quotes source post: 19093002

It depends on the engine. Our engines, no.

Thanks, I would tend to agree, that probably should be made more clear in Lake's video (if I can be a constructive critic, don't mean that in a snide way, Lake is very helpful). Even for some engines where it might make sense, it still isn't possible which also should be noted in the video. For example my Mezger it's not possible (but it's a true dry sump) and it's also not possible for my Audi Q5 2.0T. Only would work with an engine like the 996's where it's mounted upside down, but in the case of the 996 it is not advised anyway.

Quotes source post: 19093072

I find it interesting that car designers are designing oil filter locations that cannot have a pre-fill. Which likely means that it�s not an issue or else they wouldn�t do it. Now, some will say that there are plenty of design/manufacturer decisions made that don�t always lean toward the best outcome for the owner, but it would be quite risky to mess with oil delivery, so I doubt they would screw this up. In short, whatever the owners manual says is probably the way to go for oil changes, save for intervals.

Quotes source post: 19093002

When you fill an oil filter, any debris you pour in goes directly into the main oil gallery. In the past its been reported little parts of the oil container's plastic cap ring that didn't break off completely ends up falling in the filter and then gets directly blown in the main oil gallery. Thus causing a massive obstruction to flow and has been reported to happen more than you'd think. And has caused bearing melt down in some engines. So, some engine builders/techs recommendation is to not fill filter first. I've done it both ways on both my 996.1 & 996.2. On either, in my anecdotal experience, it takes at least another couple seconds for oil pressure on the dash gauge when using an empty oil filter. If you fill your filter just be certain of what pours in to it, as whatever goes in it will be unfiltered and directly injected into the main oil gallery....

Quotes source post: 19093002

Perhaps Lake was speaking more in broader generalities while Jake was speaking more specifically about Porsche flat motors?

Quotes source post: 19093630

Yes Jake was talking about M96/7engines. Lake was speaking generally but my point is that you can't really generalize and it will be specific to the engine. Some engines may not be a good idea to pre-fill and others it may not even be possible..... to the point made above, if the engine is designed this way from the start I wouldn't expect that it is a make or break kind of thing.

Jake tested this specifically for the M96, so I trust that more than anything. Good point about debris in the oil. I like to wipe everything I can on the outside before filling. Much of the debris comes from dirt on the outside falling in.

You can prefill most oil or fuel filter safely, safest way is plug the center hole and prefill using the outside smaller holes around the filter. center holes are filtered flow and outside hole are unfiltered flow. I don't prefill the M96 oil filter.

On the new filter I take a small screwdriver and make sure the drain back seal is loose. Sometimes portions are stuck in place.

We still recommend against pre-filling the oil filter. The way I look at it is that there are plenty of applications where the filter is sideways or upside down where you can't pre-fill the filter and it's not an issue there.

Timely video from Lake. You Tube

Yes, that is the video I posted in #123 which prompted me to think about this over my early morning coffee (this is when I have my Deep Thoughts by Jack Handey moments). I think Charles' post #133 sums it up in the fewest words but it is sort of fascinating that what is such a simple concept -- to pre-fill the oil filter or not -- is a topic of debate. I asked my friend this same question and he is an bona fide expert on Porsches and engines every bit as much as Jake and Charles with decades of experience. He told me he always prefilled the oil filter when it mounts vertically and said for inverted or horizontal mounts (my Audi 2.0T, my 996TT Mezger, etc) he pulls a fuse or disables the fuel pump and/or ignition and then spins it over to build oil pressure. LOL.... loves it, he spins it over "by hand", doubt many people go through that trouble. It occurred to me after posting this video that Lake has re-branded himself as The Motor Oil Geek doing more general engine stuff rather than focusing on Porsche-centric information.

Quotes source post: 19085756

The engine builder was MB Motorsports. Final update: I'm pretty much screwed. I've decided against fighting them in court. I'm taking this as an expensive lesson. I'm now living in Europe and the car was sold as a project to a kid in California. I posted a much more in-depth account in the form of a warning to others here: https://rennlist.com/forums/996-foru...l#post19111764

Quotes source posts: 19111768, 19111764

Sorry this didn't work out in your favor. FWIW, MB Motorsports was banned from Rennlist quite a few years ago.

Quotes source posts: 18571062, 19083479

Happy holidays Charles and yelcab! I have a question for you both, please correct me if my thought process is not right. Looking at yelcab's photo above for reference, humor me for a second in a hypothetical scenario where a bore has no scoring but does have a structural crack at the top of the cylinder that is serious enough to develop into D-chunk over time. Scoping from the sump even with the piston at TDC would have missed this, no?

Quotes source post: 19181285

If you had a crack like that in the cylinder, the car is un-drivable because it would misfire, spew out white smoke via the back smelling of coolant, cappuccino color engine oil, and you would have to stop driving it way before it has a chance to D-chunk the engine. That engine actually had TWO cracked cylinders and the case was sent to Charles of LNE to do a 3.8L nikky job. My neighbor is driving it now and he is quite happy with it. And you would not see it if scoping from the bottom of the engine, but it is a moot point because the oil intermix would give it away without the need to stick a scope up its ash.

Quotes source post: 19181517

Thank you for the reply and for the information you have posted here. I completely agree with everything you said but my initial thought was hypothetically if there were signs of stress before the cracking got anywhere near a chance to actually D-chunk off, and thus before the milky oil/coolant, it seems strictly theoretically that this could be missed in a sump borescope inspection. There is no question the sump is the best singular method to borescope but for engines that can D-chunk (and I thought I saw Charles post a few months ago that he's seeing more of these now) I was wondering if they would actually advise then scoping from the spark plug to check for any structural anomalies at the top of the bore. Seems like you might need to do both, depending on the specific engine, to be the most safe in a PPI. If I ever have this issue I would send to Charles as well so good call on that. Thank you for the information and insight.

Doubt we will ever truly know, but it would be interesting to know how many of these cracks/d-chunks came from failed water pump blade or from a failed AOS.

Quotes source post: 19181285

Yes, scoping from the sump would have missed it, but the engine would have had intermix with a crack like that in the bore, even without it becoming a full fledged d-chunk failure.

Yes, that makes sense, I was thinking about it more over the weekend and thought the same after giving it more thought and reading yelcab's notes. Thank you Charles and yelcab for the information, very much appreciated.

Quotes source post: 19181527

Based off what we've seen, it's mostly 3.4 996 engines that crack or have d-chunk failures, so basically the Lokasil I blocks. We do from time to time see a 3.6 with a cracked bore, but it's far and few between with Lokasil II and III blocks. That said, it might not be a bad idea to also scope from the spark plug if looking at a 996.

https://lnengineering.com/products/w...e-scoring.html "Porsche models with Alusil blocks including Panamera, Cayenne, Macan, as well as Boxster, Cayman, and 911s with the 9A1/MA1 engine should also be bore scoped to check for bore scoring, however with these engines inspection through the spark plug hole with the piston at BDC is the only option. " ( underlined emphasis my own) So much valuable information on your website and so many topics covered it is insane. On the 9A1 obviously scoring is much less of a concern but is still a concern. Why exactly is inspection through the spark plug hole the only option on the 9A1? Obviously the passage must be blocked but do you know specifically how? Since you cannot access through the sump does this mean the bore scope on 9A1 is less conclusive? Sorry for always asking you so many questions but this is what you get for knowing so much and being smart

Quotes source post: 19195035

The way I describe it, the MA1/9A1 engine has a lasagna bolted onto the bottom. Too much stuff in the way unfortunately. I still think there is value in scoping, but you have to make sure it's with a high res camera to catch even the slightest signs of scoring. Used oil analysis for sure would catch it first.

Quotes source post: 19198235

Thank you, love the visual image I am getting from the description haha Last question and I promise I am going to stop bothering you for a while: Do you know the model of the bore scope you are using? I know I have told you before but I really appreciate the information you have given me. You have greatly improved the value of RL with the information you have posted. Also the more I think about it UOA is almost more important than the bore scope in the sense that it is easier to read the results and not make a mistake. I am concerned than many people, even professionals, are not doing the bore scope procedure correctly and do not know how to read the images.

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I know lots of shops use the Snap-On scope. This is the one I have: Amazon Amazon

THANK YOU. Was going to guess Snap-On but the one you have has more and better features for the price. Fully waterproof, 360 degree 4-way articulation, all the different light settings, that thing is a steal for $400 (actually looks like even less when I login with Prime). Thanks again.

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That is a COOL scope! I wanted articulation too, but cheaped out a little: Amazon Amazon