Christopher28

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.

DBJoe996

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.

dougn

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

plpete84

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

Christopher28

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

hbdunn

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

ZnZBar 986S

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.

Clockel

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.

Christopher28

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.

Porschetech3

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..

Christopher28

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 -

Type65

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.

Lady Silver

Take the car to a professional.

hardtailer

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.

GC996

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.