AOS - Failure after 500km? (300mi)

Hi, New to me my 996.2 has a smoking issue. Here's the timeline * June buy the car. PPI notes oil leak possible from RMS. * drive it for a few 100km and note that on heavy acceleration there's smoke from the rear. Stop the car, let it sit, and most restarts the car was smoking for a few seconds and then stopped. * 3rd July - Took it to known porsche indie. Leak identified (from the IMS Solution cover plate). They did all the usual tests (???) and said AOS doesn't fail any of the tests * Approve gearbox out and fix the leak. New clutch/DMF at the same time. I also asked if it was easier to replace the AOS whilst the box was out and it would save me $300 in time. so replace AOS * They open the AOS and there's a tiny hole that they think was probably the issue * July 10 to Aug 10 - Not a wiff / sign / nothing of smoke. Including 250km of hard (2nd/3rd) in/around some twisties. * zero oil consumption that I can see * yesterday drove 70km on the freeway. A copy of wide open throttle in 3rd (love the noise) . all good * last night drove to the shops for groceries. Car was warm, oil pressure at idle around 1.5. Turned onto a little 'strip' where I can give it a little beans. 2nd to 80kph - rear full of smoke. * got home parked it for two hours. Started it... smoke... (i'll see if I can attach a video somehow. I've called the indie and they're talking about pulling intakes out, spark plugs to scope the engine etc.... The car did have some sort of engine refesh from the previous owner. Threw lots of $$$ at it. and the engine is only 5000km old.... They're not even questioning the AOS. Said 'they've never seen a new one fail that quickly'

Not saying this is your problem, as I'm not there and internet diagnosis is problematic for sure,,, but.... Brand new AOS have and do fail as reported on this forum, and its not uncommon especially for cheap after market ones. You can disconnect the aos line at the throttle body and plug throttle body port off with a vacuum cap from any auto parts store. Leave aos line open, wrap end of line with rag and insert in plastic baggy tied off lose with a tie or something so line can breath a little but not drip out oil on engine. Shouldn't be much oil coming out with no vacuum on it any more. Secure the line so it doesn't get caught up in belt or melted on exhaust. Run/idle/drive engine easy till it clears out. Probably some residual oil left in intake that will need to clear out to fully stop all smoke. If smoke stops it most certainly is the aos again. jmo

It tokes about 10 seconds to test the crank case pressure with a manometer and an old oil cap with a barbed fitting. Anything over 6 inhg and its bad. On this side if the pond there has been a UAOS developed and its worth installing if u can. Just do a search here for details.

Below is a picture of what @De Jeeper is describing. You can find the parts on Amazon. Oil cap can be found at your local porsche dealer. The oem aos can last for a good long time and it can fail quickly as well. The big problem with the oem AOS is that it struggles to process the oil regardless of whether the diaphram fails or not. So if you are running the oil level at or near full, it will most likely smoke. Especially under heavy acceleration and cornering. Same can be said for parking the car on a hill. You will most likely experience smoking problems. As mentioned, if you want to eliminate the smoking, failure risk and hydralock risk, go with the UAOS track version. It can handle up to an extra quart or two of oil above full without a problem. What this means is you never have to worry about over filling it, parking on a hill or under heavy acceleration and high G turns. Plus the diaphram is 2x the thickness of the factory AOS. Just an all around better part than the factory aos.

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While I agree DJ, and the UAOS is most certainly the way to go, many 996 owners don't have a manometer and cap with fitting. Or have the desire/time to get the stuff and do the test. Meanwhile.... Thing is many with bad aos continue to drive wondering whats wrong, not knowing what can happen. if they are going to continue to drive the car to the shop or where ever, best to have a faulty aos disconnected asap imo. And pulling that line will do it quick and easy. don't even have to pull the airbox. Might prevent a hydro-lock or partial hydrolock if it hasn't already happened... jmo

Agreed. Gotta figure out what's causing the smoking and mitigate it. Easy to do.

I had a brand new AOS fail under hard acceleration. Talk about a bad feeling�. Only plus was no mosquitoes around for days. Replaced AOS and no problems since.

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I'm sick to the stomach.

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Thanks - Yea I don't have one of those but I could, as a test, pull the line off the throttle body and plug the hole with my finger and get wife to start the car. (or see if that pipe dripping with oil)

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No one in Australia sells the UAOS from what I can tell. I can see it is a smart system.

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Doing the simple test was mainly in responce to his comment about his indy not thinking it was the new aos. If the indy put the factory or oem aos in the part should be under warrentee and it should be repaired for free. If he used a cheaper aftermarket unit in then shame on him and it should still be done for free. Unless i misunderstood and the indy did not do the install?

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The indie did do the AOS about a month ago. On the phone they started talking about taking intakes off, camera in cylinders etc.. I'm trying not to think the engine's has something catestrophic.

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Justin, I wouldn't loose any sleep over it. It's an extremely common occurance and an easy fix. You have 3 choices to fix it (AOS) in order of worst to best from my 22 years of experience owning my 996.2 and experiencing AOS failures on the street and track many times. 1. Replace the factory AOS with another one. 2. Replace the factory AOS with the Porsche Motorsports AOS 3. Replace the factory AOS with the UAOS track version. I don't know a thing about international shipping, tarrifs and emissions restrictions from the US to other countries, but at the very least, if you can't get the UAOS in your country, I would then replace the oem AOS with the second best option which is the Porsche Motorsports AOS because it can process the oil much better than the oem AOS. However, if you want the best solution, put the UAOS with the track extension on your 996 if you can import it into your country. It's the Swiss Army Knife of AOS solutions with a laundry list of advantages over the oem AOS and Pprsche Motorsports AOS. Even if you don't track your car, go with the UAOS track version because of its functionality. No brainer and no loss of sleep.

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Any noises or codes?

Factory AOS have been known to fail out of the box, as others have said. The genius behind the UAOS - @Porschetech3 - is a member of this forum, you can ask him nicely if he'll ship to Australia. I'm guessing they want to look in the intake plenum to see if there is oil and any other debris in there - you could also drop the sump / cut open the oil filter to check for any debris in the oil, doing a fresh oil filter change as part of the operation. Install the LN Engineering magnetic drain plug at the same time. That should cost less than re-doing the AOS at the outset and will ease your mind as to what is going on, or give you very bad news but at least you know where you are.

@justinbAUS Are you smoking from both tail pipes or just one? Both would more likely point to the AOS.

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These engines are pretty damn durable but their are 3 catastrophic failure points that are easily solved for and therefore prevented. 1. IMSB failure. Easy to solve, just replace the oem IMSB with an LN Retro or Solution. 2. Water Pump failure which can lead to possible head/cylinder cracking. Easy to solve, just replace the water pump every 5 years. 3. AOS failure which can lead to exhaust smoking (not catastrophic but it is a pita and can lead to your cats going bad), the possibility of intermix when the aos starts to deteriorate, as well as in extreme cases which are typically on the track or aggressive canyon carving when too much oil gets in the cylinders and the pressure cracks them which is also known as hydralock. Easy to solve for, just replace your AOS with the UAOS track. The fourth failure is a slow failure known as bore scoring. This can be easily solved for by running great oil, changing it at least 2x a year, making sure your fuel injectors are in great shape and functioning properly. My guess is your smoking is from over filling your engine oil coupled with the oem AOS inability to process it. Common Issue. But your indy is probably suggestingvthat they look at your cylinders to make sure that they arent cracking, which is probability a low probability event. Besides, you would most likely see it with intermix. If you go that route might as well get the bores scoped to check their condition for bore scoring so you can further sleep at night. I can't emphasize enough how durable these engines are if you solve for the 4 items listed above. Further, I wouldn't jump to any negative conclusions. Sure, anything can happen, but in reality, they are low probability events.

Justin, I just saw you had another thread on Gulf oil and you sent out a UAO. Have you received the results back yet?

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Both. I threw it up on YT You Tube

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Yikes! Oil smoke is bluish and smells... oily. Coolant "smoke" is whitish and smells sweet-ish. I'd pull that AOS line as mentioned earlier. Also a manometer isn't expensive and can be a good excuse to buy a blingy oil cap.

Does it eventually stop smoking after startup, or is it continuous?

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Only just sent that off. These guys usually take around a week. Will post when results are in.

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Hi - Only ran it for the length of the video and then stopped it. Haven't started it since.

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Hi - thank you for the time you spent on this (and all of you for that matter) Car has IMS solutions (for the last 8 years) / water pump 3/4 years ago, and the engine had a refresh. When the indie resolved the oil leak (it was from the IMS cover plate gasket) and replaced the clutch I had them replace the AOS as I did experience the smoke within the first week. Not as much smoke as this, however. The indie changed the oil/filter. The oil level was spot on max with the stick and sensor. And from everything I've read (my car is 2004) it has the newer dip stick for the reduced level recomendation. It subsequently had 250km of big squirts (2nd/3rd gear to 7k) on sweeping bends with my friend following. We switched cars and I followed the P and we both noted zero smoke. This event only occured Sunday night As for 'great' oil. That's turning out to be a PITA. Everything that Lake Speed Jr recommends (Driven, Motul x-cess gen2) as well as others just isn't sold here in Australia. Redline is available but that comes to $300 for 9L (quart is 0.948L) and no idea how long it has been sitting on the vendor's shelf. So I've sent off a virgin oil sample of what the indie is using - Gulf ULE 5w-40 One thing I cannot get my head around is how sensitive these cars are to oil level and how it affects the AOS. I've looked for some YT videos to try and explain it to me but not found anything. Is is only an issue on high revs? with/without wide open throttle? or high G's? Cheers

I defer to Skip (@Porschetech3) who would be the guy to answer the engineering side of the AOS. While it's a big pita when it happens, its no big deal to put a better one on.

china parts are garbage for evry bramd.. ... need to buy 3 and one will work;; maybe.. NOS is best as always.

That smoke video sure does look like oil smoke... Yes I have shipped UAOS Systems to Australia before, and all over such as Canada, South Africa, all over Europe and Asia.....The shipping cost is about $70 usd , and doesn't count for your Country's Taxes/Duties/Customs because they are all different so I don't mess with that, I just handle the UPS Worldwide shipping cost. You have to deal with your Countries Import rules ... As far as the installation goes , the UAOS System is Plug-N-Play, only two more screws to have to R&R's from the OEM AOS system, and with the Track Drain Option you have to install the new oil fill tube provided also... Any competent Professional who is familiar with replacing an OEM AOS can install the UAOS System...It's very straightforward... Also since this is a fairly new engine I would suggest to get your Tech to make sure the scavenge pumps are installed correctly ( oriented correctly) and working properly just to be safe...

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Thanks - how does one check that the scavenge pumps are installed correctly? remove sump? how would you know that they're not installed correctly without getting into the engine?

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The scavenge pumps have the number 1-3 and 4-6 cast on them 180* apart ( opposite sides) Bank 1 ( drivers side in the US) should have the 1-3 facing towards the crankshaft... Bank 2 ( passenger side US ) should have the 4-6 facing towards the crankshaft ... These can be seen just by looking at them......There are several threads in the archive on this issue with very good visual pictures...

Hi so quick update. Started the car this morning and lots of smoke that settled after 10-15 seconds. Little blip of the throttle and more smoke. So had it towed to the indie. Got an email from the indie. Their words we wait and see.

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If you're indy is going to swap out the AOS for a new one under warranty, I'd ask them if they would do a UAOS instead for the difference in part cost - the labour involved is pretty much the same.

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I'm in Australia and the UAOS is 4 week wait according to the site ;(

If the aos does test good i would just lower the oil level 2 bars on the digital read out and and call it fixed. As u have been reading the aos is very sensitive to oil level.

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I've been reading that they're sensitive. I'm still confused how over filling the oil affects the AOS. Is it that oil is sucked up through the return line?

The m96 motor accumulates a lot of oil in the heads during high g driving. The aos pulls vapor from the top if the motor under vacuum and all this oil gets too close to the aos intake. It gets sucked up and overwelms the drain back feature. Then it dumped directly into the intake. This causes the smoke and sometimes hydrolock.

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Well, if your AOS does prove to be the problem and if waiting without running your car is a concern,,,, Could always run a easy to cobble up homemade catch can system or a store bought one. Some m96 owners have done so for years. Have read here about racers on this forum permanently running catch cans...A catch can is just a more permanent setup than the one I described in my earlier post... Car should run fine without the aos connected, maybe even better. Disconnecting the vac line to aos and setting up some type of home made or store bought 'catch can' breather, would give you as much time as needed to get the UAOS.. Here is a $22.00 cheapy Amazon catch can with breather and drain that might be plenty good enough till your uaos comes in... jmo

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Hi mate - I got the results back. I posted it on Bob is the oil guy (despite my introduction to the that forum for asking about Gulf oil resulting in minor scortching....) Happy to post here. But where?

Why not post them here?!

Gulf Formula ULE 5W-40 VOA

Looks like the sample doesn't have any moly which is something you want for the M96. Take a look if you can find Millers Nano 40 or 50. It's manufactured in the UK but you may have access to it. You may be able to find it on Amazon as well. My indy used it as their oil so I ran it for 12 years in my car on the street and track and it took good care of my bores. But my indy changed their oil so i ended up going to Driven DI40 after talking to Lake about what he suggest that can be run on both the street and track. For sure, DT is cheaper but can't handle the heat as well on the track and I wanted to use only one oil that could do double duty. Oil is everything in our engines and I wouldn't skimp on getting the best you can in your M96. It's only 2 oil changes a year unless you track your car and it will be more.

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Hi Mate, Indeed I've learned that moly is highly desirable. I did this VOA to see the content because I cannot get in Australia all of the recommended oils. Millers, Driven, Motul X-Cess 8100 GEN2, Pennzil Ultra Platnium etc... just not here. There is a distributor of Driven and I'll admit I've only made one attempt at contact without success. Redline are here but they're all eBay / Amazon sellers and $300 a fill. How long has the oil been sitting on the shelf?... If that is what I have to do then so be it.

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I had Autowerks Wyong install my UAOS bought from LN engineering.

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If you can't get Millers or Driven, another option would be to just purchase a moly additive, such as LM Ceratec or Swepco's version: https://lnengineering.com/swepco-502...oz-bottle.html

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Good info on the Moly additive bonding to Aluminum/Alusil/Lokasil in the description/benefits of the Swepco /LM additive, whereas ZDDP additive only bonds to steel/iron components .. ....

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Is this stuff any good ?

@allgood read the description in the link Charles provided on the Swepco additive, it mentions the LN MoS2

@justinbAUS have you had your indie check the cam deviation to see if its within limits?

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Hi RobRoy, No. the car is still in bits waiting for UAOS. Can a cam deviation issue cause the oil to be sucked up into the AOS? or would it create too much crank case pressure?

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Neither, its just good to know and check the values occasionally.

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The engine recently got new chains / guides etc.. so they should be good for a long time ?

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Yea probably wouldnt check then until another 50k miles and then every 15k.

It wouldn't hurt to check it to make sure everything was done properly since it was a previous owner.

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Sir - you were on the money. I didn't install a UAOS as the cost of shipping etc made is a $3500 spend. So I decided to replace the AOS with a Porsche genuine and I fed back to the Indie (right at the beginning) about checking the scavenge pump. After they installed the AOS (and completedly a leakdown test (less then 10% loss across all cylinders) they pulled the pumps. Bank one (1-3) was 180 out of phase!!!!! I've just picked up the car and it is humming along.

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@justinbAUS Glad you got your car sorted !!! That is the 3rd M96 I have saved from catastrophic failure on this forum for this paticulal issue just recently ( <<<< patting self on the back ) The UAOS System was not really meant for the "good enough crowd",,( we got along without it for almost 2 decades), it took almost 2 decades to get tired all the engine failures from hydrolock, cracked cylinders bent rods, and all the labor to replace the AOS every few years, then sometimes even the OEM Genuine Porsche one fails right out of the box......Let alone the recent development to UAOS to increase durability in high g turns..And in the long run the labor saved pays for itself.. I am curious of the cost in Australia of $3500 to install the UAOS. Would you mind breaking that down for me? I'm sure others in other Countries would be interested as well..I know the Import Rules are different in every Country, with the US import Rules the most lenient, but what all does that $3500 include ?

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Private message sent - I don't like mentioning company names publically. Feel free to ask more questions. I would like to install the UAOS myself but I just don't have anywhere I can do it in little stages / take my time. (no garage... my car lives on the street)

Thanks for the info !! ....Too bad the situation of the excessive costs kept you from upgrading to the UAOS System..

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I deal with a very different Indy in Australia. They had a 996 preped for an event and as you say the factory new AOS failed - as it drove out of the shop. After doing a whole LN 3.8 Nickies deluxe bottom end. They fully supported the UAOS, given the extensive build to support. .

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The guys doing the work on my car to get me where I am basically refuses to install 'customer' parts. I suspect they might lighten up once I build rapport... but plan to chat to your guy

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The install of the AOS or UAOS system is not as hard or time consuming as some people have made it out to be...except on tiptronic cars... Before I retired from the Porsche Dealership I never charged more than 3 hours for an AOS replacement on a manual car...There is no "book time" on AOS replacement ( Porsche never dreamed it would be nessesary), so shops just charge what they "feel like" for the job...I have seen up to 10 hours charged or quoted to replace the AOS ..but I suggest that 4 hours is fair if they are competed. Most 996 owners will smartly combine the IMSB/RMS/AOS job to keep labor cost down. Labor seems to be the most expensive part of any 996 engine repair these days.. I use Kris Murphy as a routine example all the time. He is NOT a professional , just a mechanical inclined individual with good skills and has done 5-6 UAOS installs on 996.1 cars and can install the UAOS Track Version in less than 3 hours.. He has done so on all his friends cars that frequent the local Track .. All the 996 cars at this Northeastern Track use the UAOS Tack Version.. I know why and understand some shops refuse to install "customer parts" because they do a "mark-up" on all parts used to help with cost of doing business...The parts they use they are normally awarded a discount to them, then resell at a small profit along with the labor charge... Anyway if you decide to tackle this job in the future, I'm sure you can get plenty of support .....

Hi Everyone, I'm just circling back to this post that I started. So I’ve completed another 500km and I’ve just did a use oil analysis (UOA) after 1500km to see where the engine is at since it is all new to me. Since the bank one scavenger pump was installed upsidedown I'm wondering what sort of affect that would have had on the oil. the UOA has show the oil's has oxidised (within limits) but higher than I would have expected given the short distance. So I'm wondering if the upside-down scanvenger pump may have aerated the oil increasing the oxidiation value? I did attempt to ask the well known BITOG forum but I'm finding the user base there are more about post count than contribution. Any thoughts appreicated

Justin, your oil doesn't have any moly. Charles gave you some thoughts on a moly additive a few posts back. There has to be someway to get better oil in your country? I would pay up for it if it was my 996. Heck, I am paying up now for Driven DI40 in the US and previously for Millers Nano from the UK. Lubrication is everything in the M96.

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Hi GC996 Yea aware of the moly. This is the first oil change in my ownership so I've not had a change since and finding moly oil here isn't straight foward. I think I'll end up having to go to Liqui Moly Molygen oil as that's all I can get here.

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Is that an environmental law thing in your country that makes it difficult to get?

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I don't believe so. DI is imported 1200km from me, for example. Lake Speed Jr gave me a list of four oils that he likes for the flat 6 all of which isn't sold here. Pennzoil isn't in Australia at all. Motul is big in the bike scene but not so much with automotive. In referencing this Virgin Oil Analysis Results - Google Sheets If you take the Mobil 1 Euro 5w-40 SP (line 10) or the Mobil 1 Euro 5W-40 SN (Line 11) neither are sold here! and there's other examples. And there's other oils that on on this Forum and BITOG forum that are just not sold here. Why? small market. It is the same with tyres. I can see Michelin supply a bigger varity of sizes in the US and Europe, but not here. Pilot Sport 5 in the sizes I need for front and rear are not an option. But I can get them for Pilot Sport 4S. It's got to be a lack of customer base thing

It looks like your engine survived the "up side down" scavenge pump....good thing you have net been driving the snot out of it or Tracking it... Also I am shocked at the labs " normal wear metal range" most all labs here have much tighter standards for "normal".... that lab considers 65 ppm iron to "caution" range....here anything in the "teens", deserves a close watch...interesting ......

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With the pump upside down what would it have been doing inside the engine? sucking oil from the pan into the bank 1 head?

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Crazy. Sounds like the best thing you can do from an oil standpoint is network with the Porsche and racing community (including indys) to find viable sources for good oil. I can't imagine the track community and those that are serious about their engines in your country not finding good sources for oil and additives.