Air Oil Separator AOS Question

Hello all. I think I'm going to have to replace the AOS. The bummer is that it was replaced 3 years ago at around 70K miles. The car now has 103K miles on it. It is a 2002 C4 Cab. There is a lot of vacuum on the oil fill tube when the car is running and I take the oil filler cap off. You can also hear a distinct hiss of air being pulled in and the engine starts to idle rough. When I cover the oil tube with my hand, the rough idle goes away. I started wondering about this because I was getting LOTS of white smoke on start up, but only sometimes. It seemed random actually and I thought it was only when I started the engine cold and turned it off cold that I would get this. I tested this and got a little white smoke consistently doing this so I thought this is the normal behavior. Then I took a nice drive and parked in my usual spot at my golf club and after playing golf, started the car to go home and noticed smoke like it was coming from James Bond's car on start up. It went away quickly and didn't come back. The next day the same thing happened. My theory was that oil was seeping into the intake or cylinder because of the angle my car was parked. It was on an incline nose down. So the next day I went to play, I parked in a different spot where the nose was inclined up and after my round of golf, started the car and zero white smoke. I was thrilled actually. The oil wasn't able to accumulate with the nose up on the incline when parked. Then I did some more research and just decided to check the vacuum at the oil filler tube when the engine was running and it was like described above. So, I think I need to change the Air Oil Separator. My question is this: Is there an updated part number that is an updated part that makes these things more reliable than previous versions? It seems that these AOS parts, genuine or not are not very reliable. Jake Raby mentioned in one post that he has had genuine AOS's that are bad out of the box! Has this been addressed and if so, what is the new part number? If they are still infamously unreliable and won't last that long, what about installing it in a location that makes it much easier to replace? I know it goes into the block, but its really just pipes that connect to it. Can't we just in concept, extend the pipes to the AOS so that it can be placed in a place that would be a no brainer to replace? As far as I can tell, there are 5 ports on the thing, 4 of which are just connected with pipe clamps. What about making those pipes longer? The part that connected to the block, is there an adapter that could be installed to the block and a pipe run from that to the AOS? Has anyone done this? Is there a way to bench test the AOS so that I know that I'm putting in a good one considering that people on here have experienced them bad out of the box and it seems to be a royal pain in the rear to R and R? Thanks in advance!!

.. sometimes they don't last long, if you have a vacuum leak this shortens the life of them. If you drive/track your car a lot they don't last as long either. We just replaced our AOS in the spec Boxster after 10 races and it was bad. You can cut open the end to view the diaphragm. The diaphragm is the part that fails, its very soft/flexible and can get small tears in it. No upgrades other then the MOTORSPORT AOS, but it is will cost about 6x the amount as the standard unit. Extending the tubes would require some kind of bracketry and custom made soft lines, the factory lines are hard plastic with flex hoses. This would not be something easy to do. Of course we sell all this stuff on our website with free shipping Motorsport AOS: https://rennpart.com/product/motorsport-aos/ Standard AOS: https://rennpart.com/product/air-oil...carrera-02-08/ Motorsport picture:

A useful tool to diagnose a failing AOS is a digital manometer. It has been mentioned and linked many times. It is only $30 from Amazon and is a quick and easy diagnostic method. Use an old oil filler cap and adapter to make it easy .JFP & Ahsai have shown photos of this in the past

Is the same crankcase pressure/vacuum present at the dipstick tube? If so, it would be fairly easy to make a silicone and fuel line plug adapter to fit the dipstick tube...

Thanks for the answers! I've been thinking about it and I guess the main issue with the AOS is the rubber diaphragm being compromised and letting manifold vacuum to the crankcase. I guess to bench test a new AOS unit one just needs to pull vacuum on the proper port of the AOS and see if it holds. If it does it is fine but if it doesn't then it's bad. Would this work as a bench test? which port on the AOS pulls the manifold vacuum? another thought. What if one just disconnects the manifold vacuum connection and just plugs the tubes. Any negatives to doing so besides emissions related issues. Without the vacuum to the AOS, there would be no vacuum to the crank case. Would love thoughts on this. Thanks!

Another thought would be to extend the vacuum line to the AOS and put a valve on it that is easily accessible. If it goes bad just turn off the vacuum and when you need a smog check just turn it on temporarily? Once the AOS goes bad just turn off vacuum and go on your way?

Actually. I think the two hoses, small rubber hose and larger plastic hose connected to the front plenum is the vacuum line for the AOS. I've attached a photo. Don't know how to add arrows to photo on my phone so sorry if it's not clear. Can anyone one confirm that the large plastic pipe is the vacuum line for the AOS? Also what is the smaller rubber vacuum line for? It is connected to a valve that is controlled by the ECU, I presume, because the valve is connected to an electrical connector. Id like to disconnect it and plug up the hole on manifold side and see if vacuum on oil filler goes away. Then drive around with it disconnected and see if there are any negative side effects to having the AOS vacuum disconnected, but there's that darn smaller rubber vacuum line that I don't know what it does. Please help! Thanks in advance!

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Yes that large rubber hose connected to the intake plenum goes to the AOS. I applaud you thinking outside of the box but in all honesty if your AOS is bad or going bad it needs to be replaced. Also a manometer on the oil filler is the best test as if you test anywhere else you may get different data that is potentially incomparable. Don't disconnect an​​​​​y vacuum lines they are there and connected for a reason.

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If you can't find a spare oil filler cap to sacrifice, here's my $2 adapter for measuring the vacuum via the oil filler tube.... (Its one of those sink stoppers) Was pulling almost 14 in Hg with the old AOS!

Thanks for the reply! I'll get one of those meters. It will be a nice addition to my toolbox! Thanks for the info on the big tube. I found in my Bentley manual, by dumb luck, that the smaller line is the fuel vent line. Essentially this vacuum port on the front plenum is an INPUT for the crankcase vent system (the AOS) and the EVAP system. I disconnected them and plugged the hole and have been driving around and the car runs great. Also the excessive vacuum from the oil fill tube is now gone and there is no studder of the idle when the oil fill cap is off. Im going to drive it around like this for a while and see if the white smoke disappears and see if my oil consumption gets better. I've ordered a new AOS from the dealer but really don't want to do any work on the car right now. I just want to enjoy it as I've done lots of projects on it. Most recently R and R of the tip and I just got the car in Jan. I'll probably get around to changing it out later this summer. Here re is a pic of what I did:

NJS. That's brilliant. I'm going to rig one of those up. Thanks!

Be aware if you have removed vacuum from the crankcase the engine oil accumulate water at an impressive rate. Unburned fuel too. This can be dangerous. If fuel builds up in the crankcase oil it can form an explosive mixture and if it ignites... Say goodbye to some engine seals. The behavior you posted regarding removing the cap and even putting your hand on the open tube is normal. In one case with my Boxster the vacuum to the crankcase because of what proved to be a bad AOS I was unable to remove the cap with the engine running. Had I managed no way would I have covered that opening with my hand given how much pressure difference there was. However, I have to say an AOS can go bad at any time. Usually not after just 30K miles but there have been a few cases of what would have to be considered premature failure. It is possible the new AOS has suffered a case of infant death, so to speak. If the vacuum at the crankcase is excessive this is a good sign the AOS is bad. If so you should replace the AOS and afterwards be sure all vacuum lines are connected properly. If the crankcase vacuum is not excessive be sure the oil filler tube cap is not leaking. These can over time develop some "slop" where the fit to the tube and the cap fails to seal properly even though it is screwed down tight. With the engine up to temperature and idling see if you can move the cap around and if the engine reacts. Be sure the oil is not overfilled and the oil doesn't have too many miles on it. As the miles accumulate on the oil of my Porsche cars both engines are more likely to smoke upon cold start. And be sure you are running an approved oil. The wrong oil can have a foaming problem -- these engines generate a lot of oil vapor/foam -- and this can overload an already marginal but otherwise working OK AOS.

Same as my car, start to remove the oil filler cap and the car begins to change behaviour, can't remember what it did but I got nervous and did the cap back up. As Macster mentions I'd be very weary of blocking off things that usually aren't...

Hey Macster. Thanks for the input. I've been researching PCV's and the vacuum is need to flow fresh air into the crankcase and vent out the bad stuff. So so simply removing the vacuum connection is just causing the flow to not happen and like you said, bad accumulation of bad stuff. So so looks like I'm going to have to change the darn AOS out assuming its bad. I need to get an actual reading of the vacuum from the oil fill tube so I need to get the meter and rig it up. Also is it possible to test by pulling vacuum on the AOS vacuum port that connects to the intake and see if it holds. Not sure if that would work because simply pulling a vacuum might not close the valve? Thanks again!

I wanted it test the vacuum tonight but couldn't get to the store to get a drain stopper so instead Inised this: A little meatsause for dinner then oil filler cap. If somehow one day your oil filler cap goes missing then... I could feel the slightest vacuum on the cap but not enough to pull the freshness seal. I ised the oring ring from the original cap to help seal it up. Removing this and the real oil cap resulted in same behavior. There is very little vacuum which leads me to believe the AOS isn't bad. Ill redo the setup with a real oil filler that I'll pick up tomorrow when I pick up my new AOS to double check. Original oil filler cap O ring removed O ring filler tube Ragu on oring

You really need a manometer to test it properly because the correct vacuum level is ~5 inches of water, which will never register by your vacuum gauge that measures inches of mercury. 7" of water is already too high. AFAIK there are no bench tests for the AOS vapor ports anyone has posted here. I think the reason is you will need to simulate the vapor pressure and flow in the crankcase. If you remember how a regular pcv works, the flow is pressure dependent. You can test the two small coolant ports for leak.

Thanks Ahsai. I just ordered a manometer and oil filler cap. I've reconnected the vacuum lines and will pick up the new AOS tomorrow at the dealer. Thanks again all for the great info!

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While this is true, the conditions needed to get an explosion in the crankcase is very remote. There's very low stoichiometric ratio inside the engine as it runs. So, the mixture is very far from ideal to ignite, plus one would need a source of ignition inside the crankcase, and that's also very remote. It has happened, but even with a broken AOS the conditions for an explosion is quite remote. Having said that(we rarely hear of an engine exploding), the AOS is really mis-named. It doesn't actually separate the air and OIL vapor, but separates the air and liquid products, only one part of which is oil vapor. The majority of crankcase vapor emissions are partially burned fuel(products of combustion), slight amount of unburned fuel, water vapor, and a mix of light HC chains. The water vapor is more of an issue in cars with short drive cycles, because the condensate tends to stay inside the engine, and is not flushed out with a long, warm drive where the temp in the crankcase gets above ~180F. The products of combustion left over in the crankcase are fed back into the intake in an attempt to burn them again. It's a vicious cycle that is circulating the vapor through the engine, then accumulating more vapor, and shipping it back to the intake. The air OIL separator should be called the air/fluid separator. I have one on my airplane and it's a mixed blessing. It does cut down on some crud coming out of the engine, but the alternative is that some of the products of combustion remain in the oil until they are evaporated out. Most airplanes have longer use cycles than cars, so it's not a problem. The best cure is to take a long drive, and insure the engine gets up to operating temp for at least 30+ minutes. Or, never drive at all! heheh

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Ahsai, is the same vacuum present at the dipstick tube as the oil filler cap? I'm assuming yes, but wanted confirmation from someone familiar with inside... If so, I'm going to make a silicone plug for one of the manometer lines...

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Schnell, I would think so but I never tried. The only other opening on that metal dipstick tube is at where it dips into the engine oil. When the engine is not turning, that opening will be completely submerged in the oil so it's not connected to the crankcase. However, when the engine is turning, the oil level is lowered so that opening should be exposed to the crankcase. Still, that opening may see oil splashing on it. I think using a used oil cap is easy enough for me so I never bothered to try the dipstick tube. Let us know what you find.

Hey there. I'm waiting for my manometer to get here. Will be here tomorrow. In the meantime, Im curious how this AOS works, just for curiosity's sake. I also picked up my new AOS today. Its part number is 996.107.026.51 I've been examining it, trying to figure it out. I know the two smaller connections on the top are the coolant lines and I've tested vacuum on those and its good. The bottom funnel where the hose gets clamped to is the oil return line to the crankcase and the connection that bolts to the engine is the opening for the vapors to go to. That leaves to connections of which one I assume is the vacuum line to the manifold which I'm guessing is the top one, tube 5 in both diagrams. What about the bottom one which is tube 4 in both diagrams? I'm guessing that its the fresh air in? Any ideas where its connected to? Maybe the air filter box? I've attached a diagram that I found. Any ideas? Thanks for all the great info! First diagram I found. Is this the one for my 2002 C4 Cab with 3.6L engine? Or is this the correct diagram for my 2002 C4 Cab?

Yes, #5 connects to vacuum. #4 connects to the bank 2 engine case half, basically evacuating oil vapor from there. The bottom opening where #2 o-ring goes onto sits directly on top of the bank 1 engine case so it evacuates oil vapor there.

From those two diagrams it appears one has the coolant lines running through the AOS the other doesn't obviously. As a fail safe if there are multiple versions of a particular part I ask the OPC parts department to verify which part number is correct against my VIN. Usually works quite well, you might pay a little bit more than online but at least you know its going to be the right part/version for your particular car.

For 996 (3.4 and 3.6) you want the AOS with the coolant lines. The AOS w/o the coolant line is for Boxsters where the coolant lines are probably not needed due to the location of the AOS.

Thanks! I think I get it now. The coolant lines are there to provide heat so as to make sure the vapor stays vapor and doesn't condense into liquid that would just flow back into the oil. The port with 2 and the tube 4 is where the vapors from the crank case get sucked into the separator via the vacuum pulled on tube 5. Tube 5 pulls the vacuum and the big tube with the funnel on the bottom probably has some sort of corkscrew or something in it that when the vapors swril through it, the oil and vapor separate, the oil collects at the bottom and the funel allows it back into the crankcase. The upper round part with the coolant connections and the vacuum connection is essentially the PCV valve where the fragile diaphram inside somehow regulates the vacuum pressure to suck in the crank case vapors and the fat tube and funnel it sits on top of is the actual oil/vapor separator. A better design would be to separate the PCV valve into a location easy to replace and run a vacuum hose from that to the separator, which should never fail because there are no moving parts in it. It is what it is. We'll see tomorrow if I need to change mine out. Thanks!!

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Great write up! Now if you could transfer all that info with arrows etc. onto the AOS parts diagram for those of us who are more visual ill buy you a beer next time i'm in the US... haha!

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You got everything correct except the coolant part. The coolant is to prevent the water content in the crankcase vapor from freezing up the moving parts inside the AOS in cold climate.

I know this is overkill and may be TMI but for those that care some interesting info as I've heard nothing but cursing of the AOS but turns out that it is a high performance sports car doohicky: This link claims to have the "original air/oil separator" that they invented in 2006, but my 2002 911 has one. Hmmm. But interesting read anyway. https://crawfordperformance.com/coll...umption-savers Another interesting read: http://www.dietersmotorsports.com/tech/2000/4-00.html I'll report my crankcase vacuum when I find out tomorrow. Cheers!!

First diagram I found. Is this the one for my 2002 C4 Cab with 3.6L engine? I can show you were the coolant lines are supposed to go in my previous (evidently) owner modified AOS. (mine is an 04 3.6L C2) Coolant line #12 coming out of the side of the AOS in the above diagram is supposed to go to the connector to the right of the alternator, while line #11 coming from the top goes to a t- just under the coolant resz. I'm guessing in my case, line 12 was cut...about where it is broken in the diagram above, and left hanging. As shown in my photo, the other end of #12 was re-routed to the connection were line #11 was supposed to go, those bypassing the AOS. So the question is- should I reattach it when I put in the new AOS - which BTW is finally unbolted! (I generally don't run the car in subfreezing weather here in Kentucky)

Love all this information on this goofy part. Thanks for taking the time and pictures! This is perfect for future diagnosis - and just to learn. Chris

NJS. I'd reconnect them if you can. It was designed that way for whatever reason. Seems like all the higher end after market separators have connections for coolant lines. Definitely not a scientific answer! Manometer delivery is delayed. Frustrated!! So I resthaft my son's golf clubs. Have a great day!

Got the manometer today. The results are in. 5.x inches of H2O measured vacuum at oil filler during idle. Looks like my AOS is operating fine. Vacuum pressure measures 5 at idle. That's the correct reading I think. Coincidentally I havent had any white smoke since I started this thread. Thanks for all the info and help!

Nice. What problem were you trying to track down again?

Thanks! I was trying to track down a phantom! I actually think I'm over analyzing things and just need to enjoy my car. Honestly, reading these forums has made me schizo about everything on the engine. I originally staryed this thread because I was getting some white smoke on startup and then got tons of it a couple times when parked on an incline with the nose down. Nose up and no smoke. But parked nose down and after being parked a while, I got special effects amounts of smoke on startup and it stopped pretty quickly. Then after reading the forums I decided to check the vacuum on oil fill tube. I thought it was massive amounts of vacuum but after measuring it is only 5 inches of water. So I'm okay and a lot of anxiety for nothing. I even bought a new AOS and some tools anticipating I'd need to do this job. I havent had white smoke since I posted this and my oil level is just above halfway on the dipstick between min and max marks. It was just below the max around 500 miles ago when I did oil pan leak repair and oil/filter service. I always use Mobile 1 0W-40. Im curious now how my consumption will be now that the white smoke hasn't appeared in a while. Thanks and I just need to stop reading these forums and just enjoy my car!! . Thanks again all!

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Good news Squawbum! Yes, I think I will at least consider that option. Went ahead and picked up a longer piece of tubing to replace the one that was cut in half so at least I will have the option of hooking the coolant lines up, but without actually having to reach the AOS once everything is back in the engine and installed.

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I've never noticed any difference in my Porsche engines smoking behavior regardless of how they are parked. All I notice, with the Boxster, is a difference in oil level. The Boxster oil level could probably be checked with the car on its side. The Turbo senses an out of level condition and refuses to measure the oil level. The biggest factor I have observed that contributes to the propensity of either engine to smoke upon cold start is the amount of time the engine had run before it was shut off. If the engine did not run long enough to get up to full operating temperature then it is more likely to smoke upon its next cold start. The 2nd factor is how I was driving the car before I shut the engine off. I seldom (as in almost never) push the car hard then just shut off the engine. After a spirited drive which can include freeway run I drive the car easy for a while before shutting off the engine. With the Turbo the owners manual calls for a 2 minute idle time to allow time for the turbos to shed some of their considerable heat load. With the Boxster if the coolant temperature gage needle is about where the radiator fans should come on or if they are on or if the engine compartment fan is running I'll let the radiators fans come on then let then run until they shut off, or if running run until they shut off, or let the engine compartment fan shut off before I shut off the engine. (The Turbo has a 2nd fuse installed in the fuse box which causes the engine compartment to run all the time the engine is on.) But once in a while I'll come in to home in a bit of a hurry. The engine coolant temperature is not that high and the engine compartment fan is off. Usually the day is rather mild. I accelerate a bit in the driveway then coast into the car's parking space and often shut off the engine in just a few seconds (after making a quick scan over the dash to make sure everything's ok). In this case then the next cold engine start can have -- but again not always -- the engine smoking a bit. (The Turbo never gets this treatment as I mentioned above I let the engine idle 2 minutes before shutting off the engine.) The 3rd factor is the number of miles on the oil. Based on my usage as the oil approaches the 5K mile mark even though my driving style and my habits I have regarding how I drive and how I allow the engine some idle time before shutting off the engine the more likely the engine will smoke upon the next cold start. Even then the smoking is rare. What has happened is there is no smoking for it seems forever, then there is some smoking. It catches me off guard in that I don't really bother to look for it but while letting the cold engine idle a bit I catch something out of the corner of my eye and then spot a cloud of oil smoke wafting away in the breeze. About this time I happen to check the odometer and almost always note the car is coming up on its 5K mile service interval. (I really pay more attention to the trip odometer the the odometer most of the time.) BTW, I prefer to run both of my engines with the engine oil level -- measured with the oil hot (up to temperature hot) -- very near or at the MAX bar. Pretty much a sure thing that when the level drops enough -- 2 bars when measured hot -- I'll dump in a quart of oil to bring the level right back up. As I think I touched upon in a previous post the techs I have talked to say smoking upon a cold start is quite common with new and used Porsche cars on the car lot. These cars see very little engine run time. The engine gets started and the car moved -- dealers love to shuffle/re-arrange cars -- and then shut off. The techs tell me as long as the smoking is brief, over with as soon as it starts, the engine doesn't manifest any issues (like extreme rough running, varying idle speed) and the CEL remains dark the techs don't give the smoking a 2nd thought. This is pretty much what I learned to do though it is nice to have some "official" confirmation this is the right way to deal with this. I can tell you after 3 failed AOS's if the AOS is bad you might get a stumble, hesitation off idle, a slightly varying idle speed (AOS #1), or a CEL which can appear concurrently with a bit of engine stumble (AOS #2), or nothing (AOS #3). What you will eventually see though is billowing oil smoke from the exhaust. (With my Boxster with its single exhaust the exhaust just smokes, but with a car with dual exhaust outlets one might one smoke more than the other. The AOS "favors" one bank over the other when it goes bad.) Regardless of the initial symptoms, or no symptoms, when the AOS goes bad, advances to this final stage of bad, the smoking doesn't stop. In this case shut the engine off and arrange for a tow because the AOS is toast.

I had two in a row that were bad this week. One failed after the first 52 mile test loop. Replaced it, and the new one was failed when it came out the box. It was actually worse than the first...

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In your opinion Jake, is this a NOS issues from sitting on a shelf for 15+ yrs or manufacturing flaw? It would truly suck to be a customer at the end of an hourly rate for removing and replacing an engine 3 times. Flip side it would equally suck as a business to pay a mechanic a flat rate three times and not be able to collect from customer due to a part flaw, which I"m betting Porsche doesn't cover with parts warranty.

No, these units are all recent manufacture, within 2 years.Some are a few months old. I had one where the factory forgot to glue the seams together, and I pulled it apart with my bare hands... We try to find problems on our 104 mile test drives (52 miles X2)and if we are successful, thats best cased scenario. The worst case is the unit fails when the customer receives the car back, and he lives across country... Then it ruins my entire experience with them, that I worked a solid year to build. Then, whats even worse is an experience I recently had, where the customer's local shop takes advantage of the scenario. Then this shop knows who is paying the bill, and takes advantage of that. A few weeks ago this happened, and the shop charged 1,200.00 labor to do the AOS job, and there was no choice but to pay this ridiculous rate thats TWICE as much as I charge. This is another reason why I hate warranty crap, nothing about it is fair to us as the engine producer, especially when most of these parts are sold to us without warranty; yet, we have to place a warranty on them. The only thing worse than this is someone having a "weak" AOS that hasn't completely failed, but leads to excess oil consumption. In this case the owner drives the car, glazes over the new cylinders, and then we have to make an invasive repair, only because the AOS failed. We can't make excuses, we just have to suck it up and deal with it. Luckily we avoid these issues through our test work upon completion, but these are among the things that make me hate doing business.

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Are the motorsport AOS's better as far as quality and longevity? From reading this thread it seems that they might be worth the extra cost if they are better in quality (vs just being better for the g-forces of track use).

Not at all. I do not favor these units. I still have them d=fail, and I have also had them bad right out of the box. A lot of engines that we see that come here with failed rod and main bearings have these units fitted. I have stopped using them entirely.

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Thanks. Interesting, why would they cause failed bottom end bearings? Higher crankcase pressure causing oil starvation?

Since the AOS replacement job for a garage DIY'er is such a total PITA - I was wondering if someone has developed a AOS bench testing protocol such as pressure testing the coolant side and vacuum testing the AOS diaphragm side? Seems like the install and test run procedure is such a gamble with this part. I've done the replacement on mine and I never want to do that again! At least not with the engine in the car. Wow...that was one tough job for a stupid plastic engine part.

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Its not that they cause the issues, but just a contributing factor, like all the other issues we see. Yes, high pressures during deceleration are the norm. As for a testing protocol: To test this unit you must be able to pull 28" of water column depression at around 80 CFM to replicate what the engine creates for AOS load. Just this week I was given the go ahead by a major parts wholesaler to develop a flow bench to do this work, so we can provide 100% quality assurance on all their AOS units that are stocked. Developing the bench won't be easy. I plan to finish it as soon as I finish my faultless timing chain stretch measurement tools, and my "tensioner arrestors". That should be July or so.

That is awesome news Jake. I would be willing to pay extra $ for a "Raby Tested and Approved AOS", or from the vendor/wholesaler who advertises 100% QA on their stock. I think it will also be interesting to see the failure rate of new out-of-the-box units.

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But I'll not allow them to advertise them with my name, or any reference to us. Just because a unit tests good out of the box, doesn't mean it will last forever, or that it won't fail in the first 50 miles. I do everything I can to mitigate risks of responsibility for parts. Its all about keeping the phone from ringing when people want to find the next person to blame.

So whomever supplies the out of the box failed part does not replace for free? Or even the part with 50 miles on it? I understand it is a PITA to change but, hopefully, you don't pay for a second new part! When I worked for a living I dealt with numerous parts suppliers. Their big deal was their part warranty I.E. "if it fails we will give you a new part." I always pushed for labor to re-replace their crappy parts because most times labor and downtime costs were much more than the defective part. This is not even considering associated damage due to part failure and operational delay costs. They usually looked at me like I was from Mars! I can't tell you how many vendors I threw out of my facilities for this issue...Those were the good old days...NOT! My blood pressure is much lower today.

These are Genuine parts. Porsche never released the part to anyone other than Mann. If the units are bought from a distributor who sources them from a dealer, thats the best case, as long as the distributor will make good on it. This puts the distributor in the loop and their 2 year warranty kicks in. This isn;t fair to them, as they get raped by Porsche on the failed units. This is why they want me to make the test fixturing for this so badly. Often times, NO, we have no warranties on any of the parts that are sold to us, as they are classified as performance products, and are for "racing purposes". This means as the engine builder we get a big hosing job if something happens. Nothing about it is fair, but neither is life, and I've been dealing with it for the last 27 years of my life. It gets old. I am very up front about this topic at the onset of all projects with my purchasers. If they ask the wrong questions, in the wrong manner on this topic, or don't like my responses, then we never get started with them. Often times, yes, we have to. Its so much bullsh** and hassle/ disappointment to deal with some polyester suit wearing puke sitting in his cubicle asking questions, that we generally just suck it up and fix the damn thing. I get so mad at those clowns that I could tear their head off right through the phone line. I finally had a claim on an AOS that SSF Auto Parts paid to replace a few weeks ago. The shop "saw them coming" as my customer was 1,200 miles away and had a failed AOS. They paid the ridiculous 1,200.00 in labor, but that shop royally screwed themselves with me. They ended up on the black list, and will never buy another Raby developed product. Total rip off. You name it, and I have seen it with warranty repairs... SOme of them are fake claims made by guys who have friends who own shops, make up issues, and then charge to repair them... Then the owner and shop owner split the "profit" on the fraud. Been there, done that, and busted their asses after flying 2,300 miles overnight to show up in person unannounced.

Sounds like there is a huge opportunity here for someone to produce an improved aftermarket version of the AOS. Even if it costs 4x the Porsche OEM unit I think a lot of people would pay it for the piece of mind that it should be reliable. Unfortunately it often costs more to produce such a part than anyone can make selling it, probably why it has not been done yet.

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I was thinking the same thing... then, my business owner self kicked in. The cost of engineering/prototyping/development would be astronomical. Say you figure out a superior product after all the work. Now go into production and have a run of defective components. Holy ****, I don't even want to think of the backlash from customer base with delays, or worse failures that were caused by said defect before caught. All that aside, I wouldn't be surprised if someone is working on this as we speak. As far as what the end product would cost, I would say more like close to 10x price of a mass produced molded plastic piece..

Quotes source post: 14198600

I've developed two of them. Either could hit the market tomorrow. Developers don't give a damn what it costs, I don;t even keep track of those costs- if I did, it would never be completed. It costs what it costs, and we develop without monetary compromise. Thats why what I do really works. At the end of the day the risks associated with selling them were too great. There comes a time when we stop caring about successes, and have to worry more about keeping what we already have. That means no new risks. The problems with this are: -The AOS is an emissions control item. To alter it in ANY way carries heavy federal penalties. -Nothing else that I've came up with thats designed differently will fit in the stock location. We have had to mount them remotely, run hoses, and etc -Cost: No, people WON"T pay. I experienced this with the heavy duty, double bearing water pumps that we developed. They cost double, and were bomb proof, but people didn't buy them. I've had people commit to new developments by the hundreds, then we make the product and can't sell 10 of them. Been there, done that. -If people do pay, it sets the product up for failure, as the price commands that it will be perfect, and therefore ANY issues that an installer may have with fitment, effectiveness or etc makes people whine loudly because of "what it cost". -The AOS balances fuel trim. If the pressures are not correct within the crankcase the engine runs rich, or lean, and that means an AOS can kill cylinders, create oil consumption, and etc. As a developer, the actual act of making something function is the easy part. To each of you that don't do this everyday, something may appear to be lucrative, but trust me, it won't be. With distribution required, the developer/ manufacturer makes less money than the distributor, wholesaler, or retailer. Its a lot like being a song writer, you invent the art, but get the smallest portion, and the biggest liability. Luckily I do it for fun, and I make my living with other businesses that I own. That said, if anyone here is crazy enough, I'll sell them my product which is Patent Pending, and they can bring it to market. LN is too smart to sell it, and so am I.

Quotes source post: 14198625

I have been in the car-world as an enthusiast since the early 1990's. Classic cars, sports cars, and had one track/race car. Your description above sums up EXACTLY the issue that stifles most aftermarket developers and is spot on. Especially the group buy thing where everyone signs on then when it's time to buy no one shows up.

Hey guys! I think a really simple solution would be to separate the PCV and separator. The separator could sit where the AOS is normally since it won't fail and the PCV could be mounted on the front of the engine where the two are simply connected with a vacuum tube. Of course this would mean someone making this but all that would really need to made is a fitting that fit into the existing port where the AOS mounts. Then an after market separator. You connect it's crankcase ports to the new adapter and crankcase port from bank 2, connect the coolant lines and output port to the original oil flowback port the vacuum line to a PCV valve mounted on the front of the engine. The separator is never going to fail since since it has no moving parts. If the diaphragm on the pcv fails than you simply change it out. A small PCV can easily be mounted above the left side intake manifold. Then this AOS issue would be a non issue and changing it would be an easy DIY and probably make Flat 6's life much easier with respect to AOS related issues. Would this work?

The issue is the chamber has to be so large to accommodate the power levels we are working with. What you have described is one way that I have done this. The issue is the large chamber has no where it can be fitted in the engine bay. At the end of the day, issue #1 is Federal Emissions laws. We can make these things work on non- street cars very easily, or just do away with an AOS completely (which I do for track cars all the time). I have already designed an orifice based arrangement that allows the chamber size to be variable, based on performance of a given engine, allowing one AOS to be utilized across all 9X6/9x7 vehicles from 1997-2008. Making it work is the easiest part of this. The rest of the issues come from a non- technical perspective. Unfortunately, a company that has a lot to lose can't offer this, which is why its been at a stalemate since 2007 when I first came up with it.

Quotes source post: 14190343

Sorry to resurrect a thread from almost a year ago but I'm still confused about the coolant connections to the AOS. Is the coolant flow there to heat or cool and why does the Boxster not have any coolant connections to the AOS - can't be that much difference in engine operating temperatures between 996 and Boxster. Any potential issues created by bypassing the coolant connections to the AOS on a 996?Thanks.

The coolant is to warm up the AOS to prevent icing in the crankcase vapor. The difference in Boxster is the location of the AOS that makes the AOS less prone to icing. I don't expect issues to bypass the coolant in warm climate regions.

Quotes source post: 14881946

Can we not connect the coolant and instead heat it electrically? If the AOS has only a tiny amount of electrically heated coolant, any intermix problem will be contained and fixed with just an oil change. I don't really understand how the AOS works, or what it's failure mode is, so I may be talking nonsense. Since I'm in CA and don't have to worry about freezing temps, can I simply bypass the coolant and run the AOS dry, and never have to worry about a failure?

You can bypass the coolant to the AOS but that does not result in "never have to worry about a failure." The diaphragm inside the AOS is the problem. It fails over time from many heat cycles and exposure to crankcase vacuum/fumes. It is a cheap plastic part that will fail eventually, whether it has coolant going to it or not.