Air Oil Separator (AOS): major problem? Cost?

I settled on a 1999 996, in good shape, and for a fair price. I spoke to the car's mechanic for last two years, and he said that he know's the car pretty well, has done tires on the car as well an alignment, and only problem he know's of is that the AOS is going bad. He said it is dripping. How bad a problem is a bad AOS? How hard is this to fix? Cost for do it yourself fix, or avg cost to have a shop fix it? And - could I drive the car from the seller back home (1,500 mile trip) before fixing the AOS? Can the AOS have a catastrophic failure? Thanks guys! (ps - car has 105k miles)

You said you spoke to the car's mechanic, did you ask him how much to fix it? Best to get it done before the road trip.....along with clutch, RMS and IMSB upgrade (since easier to do while he is IN THERE) P.S. This link should give you an idea on parts/labor for this job: http://www.pelicanparts.com/techarti..._Separator.htm Porsche 996 air oil separator - YouTube

When they go, they go pretty fast. Mine went from a leak to complete failure in hours. I would not trust it to go 1500 miles. Glad you finally found a car.

Bro thats a suicide mission driving an unknown car 1500 miles with a bad AOS/OVS. The AOS on mine sprung a coolant leak 2 miles from home. Forced me to drive home the 2 miles and drop the engine immediately. You might consider a real/unbiased PPI.

1500 miles is pretty long, especially for unknown history and an AOS on it's last leg. Why not get a transporter for it? AOS can run all over the place but generally in the $1k-$1500k range, plus if you have it done 1500 miles away, you don't really have any kind of warranty on parts/labor if it fails. Which one did you end up "settling" for if you don't mind me asking?

If the car is dripping, it's likely you mean the RMS (Rear Main Seal) Check out the stickies on RMS/IMS/and AOS and do some reading. For peace of mind, most in the know would R/R all three on a 996 with incomplete service history. It can cost a few thousand dollars, but all are accessible during the same service/disassembly procedure, so there is some savings by doing all three at once. It also gives a good chance to check out how the clutch is doing and maybe install a light flywheel. So, the potential results of each failure are (mostly): RMS- oiled/fouled clutch, annoying drips on garage floor, loss of self-esteem, potential engine failure if oil not topped off periodically IMS- catastrophic engine failure AOS- mosquito-controlling levels of smoke exiting high-g corners, leading to oil/coolant intermix/general yuckiness in the intake tract, and potential engine failure

The mechanic in question (Courtney Truck Service) was recommended to me by a Rennlister local to that area to do a PPI - and it turns out that shop is the one who has serviced the car for last 2 years. Mechanic said the current owner has been very careful in keeping up with maintenance, etc. This plays into the question of whether to fly up and drive the car back to FL, versus having the car shipped down to FL (and then fixing the car here locally, instead of 1,500 miles away)...

Alpine - the 1999 996 Aero, Paladia color, full leather, LSD, etc.

I would personally get it transported and find a good local Indy to do the trifecta which should come with a parts/ labor warranty. This would also give you a chance to get to know and support the local Indy getting off to a good start. Btw, a drip can come from AOS if the brittle hose develops a crack in it.

Get Courtney to fix it, they are very respected here in MN for Porsche, they could do all the work on the car

Assuming you have not seen the car in person yet - I would coordinate the work with the mechanic, fly up there, make sure the car is exactly what you were expecting, hand over the check, have it fixed (the next day), then drive it home. But that's just me. I just would not pay the money for a car that needs a repair and then wait for it to come to me if I had not seen the car myself.

Well, I plan to have a PPI done this Friday (by Courtney, since it seems they have a good reputation), and see what they come back with. They seem to think it is an AOS issue, but lets see what a full PPI reveals. Then I will see if I will have them fix any issues, and I fly up there, or if I just ship the car down to Tampa and find a good Indy here. If there IS an issue with the PPI (AOS problem, or RMS problem), should I try to have the seller absorb part of the repair cost..?

I'm with Alpine. Start a relationship with your local guy. You'll have a warranty. It looks like a good car, and LSD is a hyper-rare, very desirable option. The prob with the AOS is that it's a $100 part that takes $600 in labor to R&R because it's such a PITA to get at. The best way to manage it is drop the trans and do all the other stuff (RMS, IMS, clutch) "while you're in there", otherwise you could be paying the same labor charge over and over again... I'd expect a seller to accommodate/split/pay for an undisclosed AOS.

Ship it and fix it locally. The MN shop may be awesome, but you'll never have the car there again so cultivating a local Indy would be my choice.

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Was this specifically agreed upon by you and seller BEFORE the deal was done...sale price to be adjusted to account for parts/labor for issues that may be uncovered by a PPI? 50/50 split (you pay half, seller pays half), 60/40, 70/30, etc.?? If not, then caveat emptor applies and you're biting the bullet on what the PPI uncovers.

Is the AOS leaking coolant or oil? If coolant, the coolant line can be pinched off and you are good to go.

OP: And, just so you are aware, AOS is a common part that needs replacement, so don't feel like there was a big issue that was found for your car. As stated above, it's a relatively cheap part that's hard to get access to. So, you generally want to bundle the AOS replacement with a bunch of other "while you are in there" maintenance items. It's sometimes a relatively big financial bullet to bite just after purchasing the car, but it will be worth it in the long run.

+1 on replacing the RMS/IMS and AOS at the same time. My AOS failed and a year later I replaced the clutch and IMS. If I would have done it all at once I would have saved a ton of $$$$.

Or buy a nice used car with new AOS/RMS//IMS/Oil Cooler/MOTOR/plugs/coils etc... from the get go........I know I'm terrible.

And, a great Jake Raby engine, right? This does actually make more sense. How much is the seller wiling to discount for repairs?

Anything more than half the cost of the AOS is too much for the seller to cover. If the buyer wants to replace the clutch and the other WYAI parts, that shouldn't have to be covered by the seller.

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No stories/worries, full disclosure, just drive and go = NO-BRAINER purchase and IMHO, the perfect/ideal way to start one's ownership experience. If only the OP will see it that way

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Let Imola do a real PPI. I can't believe you bought a car without one.

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I agree with you on this one. Other than the AOS, the other items are elective by the buyer who should bear the costs of the internet created hysteria relating to IMSB, water pumps, RMS, etc.

I didn't "buy" the car yet, and a PPI is being done this week. We just agreed on a price, and purchase was dependent upon a clean PPI. At this point I am not even SURE there is an AOS or oil leak issue, I'm just going by what the current mechanic told me from memory of working on the car. Also, I had several people recommend Courtney Truck for a PPI, and only 1 person recommend Imola (and the local Rennlister there noted that Imola was not a great choice for a PPI...).

Good you are making it dependent on a clean PPI. I have the opposite experience with my PPI among the choices you've listed. PPI was done by Courtney. Nice people. Here are the things they did wrong: 1) Found metal in oil filter. Determined it was IMSB. Even though I paid for the PPI, consulted with PO first to determine course of action. Did not indicate risks of getting an engine with existing metal debris. OK I was naive but they said nothing at all to dissuade me from the car. You can probably guess that they'd rather keep the local customer (PO) happy. 2) Replaced IMSB with LNE part but did not run through LNE"s qualification steps. Did not log serial number of IMSB or put sticker on door, etc. Did not clean out existing debris (an expensive and time-consuming process with uncertain outcome). Literally just slapped in the new part and said I'm good to go! Result: new bearing on verge of failure 12k miles later. 3) Installed a new RMS. On engine teardown 12k miles later, RMS was literally falling out of casing. I have the pictures. 4) Did not tighten all bolts on reassembly; at least one suspension brace started working loose. Had my local mechanic retighten everything they could reach. 5) After I found new metal debriis, simply replied "You'll be OK, we've never had these fail." Anyone who knows these bearings can tell you they will fail if installed in an engine with metal debris in it. 6) Stopped communicating entirely after some of the initial findings from engine teardown were forwarded to them. You can take your chances. Good luck. Remember, the value of the car is the value of the engine. That's how the market reality is today. Make sure that engine is 100% in all possible ways. Do whatever you need to to get that confidence. The rest of the car is icing on the cake, thrown in for free. Makes no sense but run the numbers and you will find the same.

If you plan to track the car at all, don't replace the AOS with the same (stock OEM) unit -- get the Porsche Motorsports version. It's a few hundred bucks more but it's bulletproof, unlike the OEM unit which will probably fail again in time. I went thru 2 OEM AOS's and finally traded up. Problem solved.

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While doing aos also do oil cooler o-rings - easy to do while you ate in there - mine were leaking ...I did aos as preventative at 60k ... Stock one still smoked bad in track day ...

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+1 The OEM AOS is crap if you ever go to a track event. If you never plan to go to a track the OEM AOS works fine, but on a track you will get smoke. Generally I don't think the smoke will kill your engine but it could kill your catalytic converters and some other stuff. I replaced my AOS for a OEM AOS a couple of years ago. I still get a lot of smoke when attending track days or slalom. I am replacing it with a motorsport AOS next week. Robert

Don't over react. If the AOS fails, then the engine will smoke and throw a CEL. If it is the AOS bellows, then it will leak between the Trany and engine on the left side and throw a CEL. if the RMS is leaking, then there will be a drip between the tranny and engine in the center, no CEL. If the IMS bombed, then there is a puddle and undriveable. Don't panic, 996's are not as fragile and some say.