996.2 Carrera 4S Bore Scoring Inspection Images and Report

Car Info and Introduction: Year: 2004 Model: Carrera 4S Milage: 62,000 Miles Miles Since Last Oil Change: 4000mi Oil: Motul 8100 X-Cess Gen 2 5w40 Additives: 2 Bottles LubroMoly Ceratec Modifications: Low-Temp Thermostat, Magnetic Drain Plug, Rennline Tunable Semi-Solid Engine Mounts, LN Spin-On Oil Filter Adapter with NAPA Gold filter, No cats (stolen), LN Single-Row Ceramic IMS Bearing installed at 16,000mi. I thought I would write up some info on my car and its cylinder heath in order to track bore scoring progression, symptoms, and what I�m doing to slow its decline. 2004 Carrera 4S - Technically fourth owner. Was owned by two individuals before being purchased by my father in 2013 at 16,000 miles. Summer driven only except for a few regretful startups and idling in the winter. Maintained first at dealer, then independent specialist, then me once I started to become proficient. I was given the car by my father at 40,000 miles, although only transferred it into my name upon his passing. Previous Service: 4,000mi ago, in 2023 I experienced constant misfires in all cylinders on Bank 2 (4, 5, and 6). I diagnosed this as a bad Variocam solenoid. At the time I had some extra cash from some art sales, a lot of free time, and decided to do a minor overhaul/refresh of the engine. As part of the process I scoped the cylinders, both through the sump and spark plug holes and discovered very light scoring/scratching in some of the cylinders. Unfortunately I did not mark which image went to which cylinder, but an example of the worst of it can be seen below: Because of the minor severity of it, and the fact I�d just spent my $6k budget on parts and tools, I decided to go forward with the minor refresh and check back on the scoring during the next oil change. I pulled the engine and transmission and replaced the following (from memory, will add additional items if I recall later): spark plugs, coils, Variocam solenoids and actuators, AOS and all associated plumbing, power steering upper and lower reservoir and o-rings, oil cooler o-rings, cam position sensors, crank position sensor, coolant hoses, low-temp thermostat, coolant, water pump, magnetic drain plug, LN spin-on oil filter adapter, belt tensioner and pulleys, clutch, clutch slave cylinder (blew old one out upon reinstallation), MAF, vacuum hoses (replaced with silicone, intake gaskets and o-rings, checked oil pickup tubes for debris and smoke tested the engine. I also tossed on a fresh set of rear tires and welded the loose baffles in the factory Sport Exhaust. Compression leak-down is good and less than 10% on all cylinders except for Cylinder 1, which suffers due to a leaky exhaust valve. I wanted to change the injectors but the affordable OEM options were not available at that time. I chose to refill it with Motul X-Cess Gen2 5w40. Previously it has used LubroMoly 5w40. I added two bottles of LubroMoly Ceratec. The Past 4000mi: Further precautions included not letting it idle upon startup, driving only in moderate weather, and not revving above 3500rpm for the first five to ten miles. I am also careful not to lug the engine and drive taking advantage of the car�s momentum. So far the car has not exhibited any other symptoms of bore scoring. Plugs are not fouled, no ticking or slapping noises, and both exhaust pipes are clean as a whistle. Inspection Results: Drain Plug: One small shard of ferrous metal on plug, small amount of ferrous powder. Oil Filter: One spec of green Variocam seal, one or two brown flakes from timing chain guides. Spark Plugs: All spark plugs show even burn with no fouling or dampness. Cylinder 1: Cylinder 1 pics are from the top (plug side) only. Cylinder 2: Cylinder 3: Cylinder 4: Cylinder 4 shows the worst scoring. Cylinder 5: Cylinder 6: Cylinder 6 shows some discoloration/wear(?) at the bottom of the cylinder. I also am sending my used oil out for analysis and will add the results when they are delivered. Conclusion and Plan Moving Forward: I will be replacing the semi-solid engine mounts with factory mounts due to the data I've read on Rennlist regarding solid mounts. I wonder if my bad exhaust valve could be contributed to this. As the car is asymptomatic and scoring is still relatively minor, I plan on continuing to drive it while saving for a DIY rebuild. I put around 5k miles on the car per year, and feel I can get at least another 6k out of it before tearing it apart. If no external symptoms prompt me next year, in the fall I will scope the engine again to check progression. When the time comes I will send the block to LN for nickies and order the Jake Raby book and video series, while doing the labor myself. I�ve never rebuilt an engine before, but there�s a first time for everything and I can�t imagine my financial situation improving to the point where I could afford an FSI rebuild. I also don't want to spend $30k on a car that's only worth $35-45k. I do, however, plan on keeping the car for as long as possible. Over the winter my goal is to purchase and install a third radiator kit and install the LN Single Row Pro bearing, as the current ceramic bearing is past it�s lifespan and very close to the maximum miles recommended. Thoughts, analysis, opinions, and questions are all welcome.

Very nice pictures for documenting .....Those spark plugs are burning clean....The bores actually look pretty good for Lokasil......I would like to see the UOA when available....Drive and enjoy !!!

�04 c4s Thanks for this. I�ll closely follow. i plan to drop my engine this winter too. did you use a lift? I plan to just simply put mine on taller jacks but I have to research the clearance I need to pull out the engine. Plan to replace the guides and chains etc. did my ims, clutch etc last winter. Will do a scope but I don�t really want to know 😅 no symptoms.

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I used the newer three-leg jack stands from Harbor Freight. I believe they're a knockoff of the Esco stands. I aways start by jacking from the rear points in order to lift up the front on each side so slide a jackstand underneath. Then I lift the rear from the motor and slide jack stands under the two rear points. Where it gets tricky is further lifting of the front end. I use a jack and a section of 4x4 placed carefully on a seam or suspension component to raise further, until the jack stands are at their max height. After that point I add sections of 2x12 under the jack stands to go even higher. I've found with this method I can get the rear crossmember 36 or so inches above ground level - more than enough to slide the engine and transmission out using the one-ton Harbor Freight hydraulic lift table. Regarding borescoping - sometimes ignorance is bliss. However, if I hadn't scoped on a whim last year, I wouldn't've witnessed the beginnings of scoring, not installed a low temp thermostat, not done everything to make my engine burn as cleanly as possible, and would've kept using the same low-moly oils and no additives. I also wouldn't've adopted a better warm-up procedure. I feel like without that knowledge my scoring would've progressed much faster than it has.

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Skip, is it me or does OP's number 3 plug look dodgy? Also, did later cars use a different spark plug? OP's #3 spark plug My '99 original #3 plug (on the left) at 40k miles.

@bradgillette , congrats on the great condition of the car and especially engine. Love to see guys refresh their engines and take care of their 996. I wouldn't be suprised if you got another decade with the engine before having to do a rebuild. But it's nice to have the skills to know you can rebuild on your timeline. Take a look at the Driven DI40 VS DT40 thread. You may find it of interest. Lots of fresh high quality and high viscosity oil may be the most important ingredient in the M96.

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Caught my eye too. I assumed it was just camera artifact. Good work on the documentation. I say drive it with the precautions you mentioned. Let us know. Maybe you'll only get another hundred or 150,000 mi before rebuild.

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Yes, I saw that and stopped to look at it again, it is burning clean but there is a slight overheating to the electrodes, ( good eye ).....it is a Denso plug so probably is a 6 heat range instead of the 5 that is called for on the 3.6 engines..( need to see the full Denso part # ) Yes, the 3.4 engines use a 6 heat range with 4 ground electrodes from Bosch or Beru, the 3.6 uses a 5 heat range ( one step colder) with 4 ground electrodes.. The Denso shown is a replacement ( cross-refferenced).. maybe a platinum/Iridium? and probably the wrong heat range ....You have to be careful with cross references on heat ranges, the NGK heat ranges 1-10 are opposite from Bosch/Beru 1-10...where the Bosch/Beru get hotter the closer to 10...the NGK get colder closer to 10 ......and a heat range 5 in Bosch/Beru is a heat range 7 in NGK....confusing I know.. ..but there manufactures are not "bound" to be like each other or have standardized rules..( no standardized SAE rules on heat range identification numbers)

That plug look different, I also use the Denso iridium plugs, but keep the gap at .031 + - .004 tolerance.

Just keep doing an engine oil analysis and keep an eye on the iron.

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I've kind of set a goal to get my life in order enough that I can afford the rebuild in two to three years - but if I can drive the car during those years and squeeze some more time out of it, that would be great. The downside to getting my life together is that I likely wouldn't have the free time to do the rebuild at that point. Is there a specific plug you'd recommend? Is there any downside to running the plugs I currently have installed? Trying to stretch dollars so if I don't absolutely need to change them I'd rather not. Also have had trouble with some plugs causing alternator whine in the radio - I have a hardwired FM transmitter in order to connect aux devices to the MOST system. I'm new to the oil analysis, and have read some threads about what to look for, so forgive my ignorance but what would high iron content signify? IMS bearing race wearing? I know that copper content would point towards other bearings wearing.

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For bore scoring, used oil analysis can be very useful. We often see increased iron, aluminum, and silicon levels when there is bore scoring, even when other symptoms are not present. As far as IMS bearing wear, the particles generated don't come up in normal used oil analysis. What you want to look for is ferrous debris that looks like silver glitter in the oil and filter.

Finally got the used oil analysis back from Blackstone. Took a few weeks. They say silicon is high, but I also used RTV to reseal the sump as part of the last oil change. Any thoughts?

Quotes source post: 19671860

I'd recommend resampling in 1000 miles to be 100% sure if you have concerns about bore scoring. If I'd expect the silicon, aluminum, and iron levels to probably be the same or worse even with a much shorter OCI if you do have bore scoring. I always get a kick when I read BS's comments about the IMS bearing. :-) They should know that without a particle size and count test you can't use used oil analysis to detect a failing IMS bearing. At least they've gotten better than telling people that the high silicon is because the air filter is dirty, so I guess that's an improvement!

***UPDATE 5812 MILES LATER*** The car is now at 67,812 miles and I thought I'd give an update. Haven't changed much other than removing the semi-solid mounts for factory style liquid-filled. Here's the state of the spark plugs: As you can see, they're all even except for Cylinder 1 - which is toasted. Last year I did a leak-down test, not because of any symptoms, but because I like to torture myself about the health of this engine. Every cylinder was good except for Cylinder 1, which had poor compression due to a leaky exhaust valve. I decided to run it for a few thousand more miles and see it it got worse, and eventually I developed an uneven idle. Felt like misfires but no codes. I got a new borescope and decided to pull the headers off and try and get a closeup video of the leak by airing up the cylinder with some thin oil to watch leak out. I then made an odd discovery: The leak was gone! My current, uneducated theory is as follows: Carbon buildup on the valve prevented it from sealing. Due to Cylinder 1's low compression, the ECU sent more power to that coil/plug, causing the spark plug to wear prematurely. This caused the uneven idle, even though the valve was now sealing properly. I'm still going to do more tests and try to scope all of the valves, but I think I no longer need a head rebuild - which is wonderful, as the car has a few other expensive needs. AS FOR THE CYLINDERS... Here's the current state of the cylinders, only from above this time. Surprisingly they look pretty good. The Motul, Ceratec, and progressive warm-up procedure (under 3.5k for fifteen minutes) must be doing its job. There is, of course, more streaking in cylinders 5 and 6. I'm going to re-scope it with a different scope and see if the difference in light source provides any more info. Cylinder 01 Cylinder 01 Cylinder 01 Cylinder 02 Cylinder 02 Cylinder 02 Cylinder 02 Cylinder 02 [img alt="Cylinder 03 You can start to see here on Cylinder 03, along with the subsequent cylinders, where it starting to show patches of light uneven cylinder wear, possibly caused by ovalization?"]https://cimg0.ibsrv.net/gimg/rennlist.com-vbulletin/1800x1013/cylinder_3_07_c2d527b28ca0fd8deb38687e3e80cdb2ff09b5bb.jpg[/img] Cylinder 03 You can start to see here on Cylinder 03, along with the subsequent cylinders, where it starting to show patches of light uneven cylinder wear, possibly caused by ovalization? Cylinder 03 Cylinder 03 Cylinder 04 Cylinder 04 Cylinder 04 Cylinder 04 Cylinder 04 Cylinder 05 Cylinder 05 Cylinder 05 Cylinder 05 Cylinder 06 Cylinder 06 - Car has been sitting for about five months at this point so there's oil pooling in some cylinders that usually isn't there. However, the fact it's most present in Cylinder 06 makes sense. Cylinder 06 Cylinder 06 - This damage wasn't visible in the previous scope. It's definitely more scuffed up than before, but I have only these two data points so far. Will be interesting to see what it looks like a year from now. I'm going to switch to a heavier weight oil and continue with the Ceratec. It could be snake oil, but it could help slow things down. I need to pull the engine out to replace my throw-out bearing (Pulling the trans together with the engine just works better for my jack-stand and hydraulic table setup), and I'm also going to replace the injectors while I'm at it. Wanted to do it two years ago but they were prohibitively expensive during the pandemic. Its LN Ceramic single-row IMS bearing, installed in 2013, is now just over 51k miles. So I'm going to replace that while I'm in there with an LN Single Row Pro (dual row in the space of a single-row) or The Solution. The right thing would be to go with The Solution, but I'm also trying to make a little bit of spare cash go a long way. I'd also like to check my cam deviations but need to finish reading the PIWIS 3 thread.

Bores look very good. What oil weight are you running currently? Ovalization is a result, not a cause. The patches you see, you wouldn't be able to feel them if you could reach in there and are far, far away from what scuffing looks like. They're are at the spot where side loading of the bore by the piston on the power stroke is greatest. It is this force that over time ovalizes the bore. In this direction (perpendicular to crankshaft) the bore diameter increases, not diminish. The latter perhaps being your train of thought for being a cause of the patches. In another note: the severely worn spark plug, are you certain it was changed at the same time as the other 5? I'm not well versed on the capability of the 7.2 gen DME in the 996.2 and whether it can fire a plug multiple times but it would need a hell of a lot of multiple firings to cause that amount of tip erosion. If you'd want to observe whether that plug indeed caused the misfires , swap it with the plug in cil 2 and check if the misfires stay with the plug. Moot, if you have observed this by fitting new plugs altogether. Thanks for sharing your pictures!

The Ceratec is certainly helping. You'd get the same result with running Driven DT/DI. Going to a 50 wt will also help for sure as that will bump up the HTHS vis. When you check cam deviation, be sure to also check fuel trims at the same time. I would also smoke test the engine while you are at it. Both are things we recommend as part of our strategy for bore scoring prevention and mitigation.