AOS questions

Can anyone help me with my AOS replacement? This is a 2001 996 coupe - I believe it's a .1. I'm knee-deep into this project. I have the airbox, throttle body, alternator, coolant tank, and left plenum out. I'm now trying to remove the old AOS, but I have a couple of questions. First, let me describe the incidents leading up to this project; About three weeks ago there was a puff of white smoke when I started the car, which I ignored. Ten days ago, after a ten-mile trip, and less than a block from home, I noticed a steady flow of white smoke that quickly grew much larger. I quickly shut off the motor, then restarted it and drove the last 200 yards to my driveway. (I tell myself that had their been white smoke between that first puff and the day with the heavy burst of smoke, I would have noticed, but I'm not happy that I didn't investigate that first puff right away.) Back to the dismantling: When I removed the plastic piece (the rear-most one) from between the two plenums, there was oil in it. A small stream of oil totaling maybe an 1/8th of a cup came out during removal. So one question; is it unrealistic to hope the plugs weren't fouled, or more serious damage wasn't done by the oil? (Note; when I shut off the motor and restarted it, as I was coming home, it started and ran normally that last bit.) That's one question. Another is a minor one; when I was trying to remove a one-inch hose from the AOS, the small flexible plastic ring that you're supposed to press on to disconnect it broke off - just the ring. Does that mean I have to replace that hose, or is the ring just a guide to grip the connector and show where to apply pressure? Finally, a personal opinion; most write-ups declare this to be a difficult job, but I've seen a few posts or videos (elsewhere) saying it was easy and they knocked it off in a few hours. I'm sorry; that's bunk. I'm not a professional mechanic, but there's no way this is easy even for pros. Even if you assume all the hoses just pop right off, and every nut and bolt will give themselves up freely, there are still a number of other daunting challenges. THANKS IN ADVANCE to any help and suggestions.

Here is some encouragement - replacing the AOS with the engine in the car is a very difficult job and a total PITA! I did it over the span of about 4 days and my left arm was so beat up I could barely use it. There are no tricks, so just be methodical and have a lot of patience. Walk away if you get stuck. I challenge anyone who says they can do this in just a few hours. Now, for some advice, get the UAOS. Search on this forum for the UAOS, install once and never go back there again.

yes it's a bitch! One of those inspection cameras with the long wand helps to see whats going on....since you're working blind. i replaced the rearward 10mm bolts that secure the intake manifold with socket heads. that way you get a 5mm, 6 inch long socket head ball driver 1/4 inch drive from harbor freight and a small 1/4 inch torque wrench ratchet bicycle tool. makes life much easier

I did this on my .2 so slightly different but I didn't find the job as hard as others made it out to be. Yes, it was challenging and requires you to be comfortable working in tight spaces but I had it done in 2 days with taking my time, pictures and brakes working on my first Porsche. I wrote this DIY with photos - hope you find it helpful. The thread is also full of good info. https://rennlist.com/forums/996-foru...l#post17404197

Very impressive photographic record. I wish my car was a .2

I�ve done it twice on my .1. The easiest for me was lowering the engine and getting at it from underneath. Especially because of the rubber hose on the bottom. The rings on the hoses have integrated clips so most likely you�ll have to replace the hose. Hopefully it�s the top one. Here is a pretty good tutorial. https://www.pelicanparts.com/techart..._Separator.htm

If you're doing the clutch and IMS, it's also accessible from underneath (trans side) while you have the trans out and the engine lowered. I've seen it done on jack stands, but I wouldn't do it without a lift you can stand under. Still a PITA though.

Go from below. Done it in 2-4 hours. Not fun, but doable. The right combo of floppers and sockets from the bell housing area once your aforementioned parts are removed. Just be patient. Remove the driver intake manifold as well.

Hey thanks for the post. Two questions, if you can help; As I was buttoning things up, I accidentally pulled out the very thin black plastic vacuum line that comes from somewhere near the starter motor and goes to the little grey plastic thing just on top of the alternator. The car started and runs, but I'm wondering how important it is to get that line reconnected, or can I put it off -- indefinitely. The line is maybe one or two millimeters thick - the thinnest of all. More importantly - as I said, the car starts and runs, but there's still a lot of white smoke, even after two or three minutes of idling and one or two revs. It doesn't seem to be clearing up. How long should it take for it to stop smoking, it I fixed it properly? I'm getting worried. Thanks.

You need to test it with a Manometer, I don't know what AOS you inswtalled, but there are many cases of people getting faulty Porsche OEM AOS's right out of the box. And yes it may take a few days to stop smoking if you have coated everything in the engine and exhast with oil. And yes you need to hook up the plastic vacuum line, it will plug into the rubber boot that connects the intakes together. Otherwise you are pulling in unfiltered (dirty air), and will cause the CEL /fuel trim to be out of spec, and also the intake resonance flap will not work..

Ugh! WHY wasn't I more careful with that vacuum line! I'm guessing I'll have to pull the throttle body again... will that give me enough room to reattach it? 2. When I start the car now, there's no smoke at first, but after a minute or two it comes back. I also did that test where you pull the oil cap off, and there's definitely a vacuum in there - it's a bit hard to pull off, and the idle drops when the cap is off. 3. I don't know which brand AOS I bought, but it wasn't OEM. It was $46 from PartsGeek. 4. When you say "a few days" to clear up... I've seen plenty of warnings that a bad AOS can do serious damage to the engine. How long do I dare run it, without knowing for sure what's going on? Thanks -

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Sorry to be the bearer of bad news, but Porsche branded AOS have a bad reputation for not lasting long, and non-Porsche branded ones have an even worse reputation. If it turns out this AOS is bad or when/if it fails I would highly recommend looking into the UAOS, it is a far superior product in every regard. It is truly a permanent fix.

Take the car to a professional.

Answer to Q 4: you've replaced the broken part so that risk (of hydrolocking the engine due to large amounts of oil in the intake) is nill now as it would already have happened. IF your new part is working as intended that is. You should check this by getting a reading with a manometer that can read vacuum. Search for the spec to know what your reading means. High vacuum is bad, a little is good and from what you described I'd say it's good. Revs changing when taking oil cap off is normal as it introduces unmetered air to the engine/combustion.

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Christopher, Save yourself many headaches by getting the uaos instead of using the $46 aos from parts geek. Same can be said about the factory aos. These things are weak and fail quickly and often. There is an entire thread dedicated to the ultimate air oil separator (uaos) that you want to read.

Ugh...having replaced my AOS I cringe at the thought of putting a $46 Parts Geek replacement in there with all the work required. There is something to be said for OE Porsche replacement parts, or the UAOS forever fix.

My follow up; (with thanks to everyone who made suggestions) I tackled this job myself, after reading a number of comments stating that it wasn't that hard to do - some had completed it in a couple of hours. I ordered a new AOS, set to work, and finished up the job yesterday. )Apr 16, 2022. For anyone considering doing this replacement work yourself, here are my stats; The car was up on the jacks for about two weeks. I spent between 1 and 7 hours working on it nearly every day, since I first removed the air box. The major hang-ups for me were the alternator, the coolant tank, the gas line going to the fuel rail (I had to remove it to make room to get the coolant tank out) removing the center plenum (the second one) removing the sixth bolt at the back of the air intake plenum, loosening various coolant hoses and the rubber boot at the bottom of the old AOS, uninstalling the old AOS, installing the new AOS, reconnecting the various coolant hoses, tightening the sixth bolt on the air intake, reinstalling the coolant tank, reinstalling the alternator, and reinstalling the 2nd plenum. Everything else was easy. After all that, the car started... but is still emitting heavy white smoke. There are two possibilities here; either I screwed up the AOS during installation, somehow, or I should have gotten the problem diagnosed by a professional shop, because it now seems likely the problem wasn't the AOS at all, but score boring or something equally disastrous. I'm going to talk to the Porsche shop down the road tomorrow & get their opinion. My car is a 2001 996 .1, incidentally. Thanks again.

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I have the same car, and I feel your pain. Stick with it and keep us posted. Your determination to get this done yourself is admirable. I'm hoping that my aos will hang on until I can get the uoas and have it done by my specialist. My cars going to be worth more than a new 911 at this rate. Or, I'll have spent more on it. But I'll own it, and I love it. There a certain madness involved perhaps... 🤔

Does anyone have the torque number for the two bolts that hold the engine in? (next to the engine mounts). Thanks to all for the comments and suggestions. I didn't learn about the UAOS until I'd already ordered my standard part, so I just went with that. It seems to be working well. One further comment about the relative difficulty of doing this job; first, it's likely the mechanic doing the work (me) may not be a particularly skilled or experienced one, and (2) the job can be considerably easier or harder depending on if the car was garaged all it's life, or sat outside and was driven through, say, 20 Pennsylvania winters, versus a hanger queen. Last; if you're doing this replacement, and you're reconnecting the last few hoses, be careful when you're reattaching the tiny vacuum line that comes out from close to the starter motor. There's nothing holding it in but friction, and if you pull on it with any force, it'll come out. If you've already put the near plenum and throttle body back on, they've got to come out again, and probably the back plenum too.

Anyone know the book hours for this job?