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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).
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.
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).
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
Last edited by Porschetech3; 01-30-2023 at 03:42 PM.
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.
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.
How much of the d-chunking events that occur in the M96 are actually caused by aos failure?
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...
Last edited by Porschetech3; 01-31-2023 at 03:54 PM.
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...
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.
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
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?
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?
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
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?
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..
Originally Posted by GC996
5,000 failures is enough to keep the RL 996 forum busy with bad news.
Yes and enough to keep the bad info flowing when the other 170k people claim it is all "overblown"..lol
Originally Posted by GC996
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.
Last edited by Porschetech3; 01-31-2023 at 05:45 PM.
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.
01-30-2023, 12:49 PM
