Air Oil Seperator

Hi all just a quick question to you all....... Had the AOS go on my car about 1000 miles ago - it happened at high revs, about 6500rpm, and boom a big plume of smoke out the back of the car and subsequently smoke on startup. Disassembly of the intake showed the tell tale signs of oil in the intake etc etc ....... So AOS was replaced with a new one from Porsche by my local indy. Fast forward to yesterday - high revs accelerating hard and you guessed it Boom - big plume of smoke out the back and its now smoking on startup again with signs of oil in the intake again :sad: In between the two events its done about 1000 miles, 600 of those in 2 motorway journeys, 200 miles in 30minute A road journeys and the the other 200 local stuff. It has behaved faultlessly between these two events. Anyone else ever had experience of a dodgy AOS from Porsche or heard of something like it? The main man at my Indy is away until next week on holiday so its going to stay in the garage at home until then. Is there a warranty on porsche parts? ....*****... :x

On the US forums theres a few comments from jake raby that lots are faulty out of the box, and some racers saying they don't last long on track. Jake's shop apparently has a test rig for them to test before fitting he has so many fail... Take it back to your mechanic, Porsche will spring for another and should pay his labour. Did the mechanic get the aos for you? PS jake raby is apparently the #1 m96 builder in the US.

Yes .. and yes .. also .. er yes .. Bloody things .. chocolate i tells ya .. I fitted one to a Boxster for the vacumn problem .. whistleing , couldnt remove the oil cap etc etc ..after fitting the " new one " it smoked out the workshop ! .. opposite fault to what i had .. fitted another and all good. Hell of a job convinceing the Boss it was a Faulty AOS though .. had to argue my point to replace it .. stood my ground though and was right Ive had x2 faulty new ones in the last 6 monthes .. one lasted about similar to yours before it went . At the end of the day theres only 2 things i can think of that dump oil into the inlet track in large amounts .. AOS and Bore score .. Bore score dont go away when you fit an AOS ! Yes there is a warrenty .. indy will end up paying for the labour though .. porsche only pay that if they do the complete job ... we payed the labour cost on both of the above .

Demort..... excuse my ignorance but how does bore score put oil in the inlet..... or is it just the same symptom - ie exhaust smoke. If its bore score wouldn't it just be one pipe thats smoking? ( starting to worry that its more sinister than the AOS now!) As for the labour issue, if Porsche warrant their parts then surely they must bare some responsibility for the labour as well! To take that idea to its extremis are you saying that if porsche deliver a batch of faulty valves that kept snapping and righting off engines they would only spring for the cost of the valves and not the engine rebuilds?

I once bought coil packs from euro car parts that failed, they paid me the original labour to replace them, thats why I thought OPC would see you right. Anyway its moot if you took it for an AOS to a garage and its failed so quickly, your contract is with them and they should fit you another and chase the costs if they like. I think usually the warranty is 12 months on parts.

Bore score is grooves in the liner , oil by passes the piston rings via these grooves and ends up being pushed up to the valves by the piston , some will go into the inlet mainifold via the inlet valve . This is mainly in extreme cases of bore score .. Obviously you will have smokeing both from the oil in the cylinders and the oil from the inlet mainifolds , ie .. I saw a Cayman a while back diagnosed as an AOS , large amount of oil in the inlet mainifold so it seemed correct , only after an AOS and a bore scope check did we find it had severe bore score damage . My point was there is only 2 ways of oil getting into the mainifold and if you had bore score to this extent then it wouldnt go away for a bit after a new AOS was fitted .. so your new AOS is indeed faulty . Regards warrenty ... the garage will pay the bill for replaceing it , they can recoup the cost of the part from Porsche but not the labour cost .. Porsche say for failed items like this then they have to diagnose it .. which means the garage has to take the car to them .. they inspect it and may or may not agree the part has failed .. if they dont the garage has to pay opc costs. Most indys would diagnose this them selves so can only claim the parts cost and even then it can be a struggle .. Porsche are not that fond of Indys !!!

Just to update this thread.... I spoke to my Indy initially who agreed that he thinks it is the AOS, he asked if i wouldn't mind speaking to the nearest OPC. I spoke to them who asked when i could deliver the car to them - They are happy to diagnose if it is the AOS and replace it under warranty if it is indeed gone. The caveat being that if its not the AOS then i will have to pick up the labour costs. Parts apparently come with a 2 year warranty. Maybe they are aware of a batch of bad AOS's or an ongoing quality control problem with their supplier? Rennlist seems to have a couple of threads anecdotally confirming failures of AOS's on installation or after a few miles, backing up Demorts experience of multiple failures.

I recall that PPBB fitted a Porsche motorsport AOS instead of the road car version- anyone know much about it?

I had the motorsport version on my previous car - it failed at 40k and if i remember correctly cost 3 times the price of the standard one! Also from memory the plumbing was different as the standard one wouldn't fit in its place?

So...... an update.... OPC had the car for nearly 2 weeks and can find no fault with it! The tech's test drove it multiple times in an effort to replicate the symptoms that i had before taking it to them and no joy :dont know: The only thing they reported was that they were shocked at how sprightly it was for a 996! They have agreed to have it back and revisit the warranty issue if the symptoms return at any point.... guess time will tell :dont know:

Hi Toohey - have you done the AOS test, where you see what level of vacuum is being pulled at the oil filler cap. When AOS fail, apparently the vacuum is much greater (some apparently cant remove the filler cap, with the engine running). You need a slack-tube manometer to measure this. I built one out of clear pipe and an old oil-filler cap. Then filled with a bit of water (not oil) with food colouring. I made sure there was a lot of hose between the u-bend and the oil filler, in case it was pulling a big vacuum, I didn't want water in my oil. There are instructions on rennlist, showing how to build the manometer. But hopefully the attached pictures are self-explanatory. The pictures are borrowed from other threads and show how its measured. At this point get the car up to operating temperature. AC off, idle speed of less than 1K, and measure how many inches. Jack raby, on other forums, has said anything more than 6.25 inches and he is suspicious of AOS and more than 7 inches and its definitely failed (some get readings of 12 inches. If you are near me (am Leighton Buzzard) - happy to do the test with you, as I haven't binned the manometer I built.

https://www.renntech.org/forums/tutorials/article/255-an-inexpensive-way-to-test-for-a-bad-aos/