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Hobbes

Air Oil Separator Replacement (AOS)

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Air Oil Separator Replacement (AOS)


EDIT: Fixed text boxes to see text better. This is an AOS DIY that walks you through the process of replacing the AOS. This is for a 2000 996 C2 Cab, six speed. I tried to be as thorough as I could in writing the DIY. If there is something left out or lesson learned from your personal experience with the AOS and or this DIY, please let me know so I can incorporate it into the document. Regards, Ken How do you eat an elephant? -- One bite at a time!   Air Oil Se

 

Edited by Hobbes
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spectacular DIY. Any idea if it is the same process on 2003 996c4s? (I did coolant tank replacement follwing some DIY but after hours of trying to get the tank out had to lower the engine that replacement alone took me a day).

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Thank you.

To be honest, I do not know how different this would be for a 2003. If I had to guess, there wouldn't be much difference as far as the main parts removed (e.g., coolant tank, alternator, etc). Getting the coolant tank out is a little tough, but getting it back in took an equal amount of manipulation to get it back in. I had to remove the fuel lines by the coolant tanke and the electrical connector on the bottom of the coolant tank and with a right combination of twists of the tank, I was able to get it out.

Regards,

Ken

spectacular DIY. Any idea if it is the same process on 2003 996c4s? (I did coolant tank replacement follwing some DIY but after hours of trying to get the tank out had to lower the engine that replacement alone took me a day).

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I bought AOS from the porsche dealer (so it is VIN matached, correct year etc 996.107.026.51). My car is 2003 C4S and I have correct AOS but the dealer could not find accordeon pipe that connects to the bottom of AOS (number 10 on Pet picture). In fact when oerdered what is marked as number 10 comes as a small beded pipe 1/2 in.

AOS also has a red ruber ring (see attached pic) so it is unlikekly that accordeon pipe fits it (in fact it doesnt as we tried with the dealer). I really dont want to take everything apart to find out that i need some other part.

Does anybody know what the story is with this new design of AOS and what connects to the big pipe?

post-20455-0-83124500-1306177122_thumb.j

post-20455-0-91780300-1306177130_thumb.j

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996 107 175 50 is what I show, for that model and year it's a hose though not a bellows.

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yeh, well, that hose I got and it is 1/2in outer diameter and it is bent and clearly not even close to fit the big pipe. PET picture shows AOS of new design where this little bent pipe (996107175.50) is replaced by plastic (the end of it is where ruber ring "2" goes onto). so my question remains. does anyone know what the parts in there like? is there a pipe already that doesnt get changed with AOS?

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Thanks so much for such a constructive and comprehensive DIY. My 996 has been resting in the garage for some time and waiting for a new AOS to arrive. I'll follow your guide :)

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Hi, I am just putting my car back together after following you DIY. One question, is the alternator removal necessary? Is it to reach the last upper intake bolt?

Thanks, it was an excellent writeup!

Johan

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If you go in from the top, unless you drop the engine significantly (which requires disconnecting lots more stuff), you'll need to remove the alternator. There just isn't enough room to get to all the intake manifold bolts.

Removing the alternator is not all that difficult, it is just a few bolts and nuts.

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Hi, I just finished reinstalling the intake bolts, and I could reach them all from the left side of the intake. To be honest I don't know how you even can reach the last bolt from under the intake?

Also, I realized that removing the coolant tank isn't necessary either. There is enough room to get the intake bolts out anyway. Neither is a lot of work, maybe I would have saved 1,5 hours. The alternator was a nightmare to get out, but simple to put back in.

Maybe a tiptronic is different? Could I have something more mounted under the intake, which make it impossible to reach the bolt from under the intake?

Regards,

Johan

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Maybe a tiptronic is different? Could I have something more mounted under the intake, which make it impossible to reach the bolt from under the intake?

Good work so far.

The rear intake manifold bolt is reachable, I remember doing it with the engine in car, and only lowered the engine down about 1 inch (very slightly loosened engine mount bolts). I had already removed the alternator. I did not remove the coolant tank.

Yes the alternator can be a bear to remove/install, but you can manhandle it with some carefully placed wood (to prevent metal damage as you pry) and a pry bar.

Going in from the top and removing the intake manifold, the tip should not be different from a manual gbox, aside from perhaps a few extra coolant hoses in the way. If you are speaking about an AOS bolt though, I am not sure. I have read the AOS job can be a little more difficult with a tip.

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Ok, got an hour this evening, and decided to put the car back together. Unfortunately I could not find out where to put the coolant hose from the oil cooler (this one was broken for me, creating a massive coolant leak), and unfortunately I was not smart enough to take a picture....

I think it was attached to the coolant reservoir, but the inner diameter of the hose is only 8 mm on the oil cooler side, but on the coolant reservoir it looks like maybe 12-15 mm.

Anyone who know if I am going in the right direction?

Besides this it worked out gret, I just need to get it to the shop for a vacuum coolant fill!

Thanks,

Johan

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Yes the oil cooler hose goes into the fitting on the side of the coolant expansion tank, near the top.

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Hello,

I just changed my AOS and everything seemed to go smoothly, but on restart the car runs rough, stalls after a few seconds, and makes sounds like small backfires.

i was thinking maybe i have a leak somewhere. would this be the correct symptoms? maybe i didnt put the throttle body on correctly? i had difficulty with that part, but i thought i got it on there right.

any ideas?

thanks

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Hello,

I just changed my AOS and everything seemed to go smoothly, but on restart the car runs rough, stalls after a few seconds, and makes sounds like small backfires.

i was thinking maybe i have a leak somewhere. would this be the correct symptoms? maybe i didnt put the throttle body on correctly? i had difficulty with that part, but i thought i got it on there right.

any ideas?

thanks

just to follow up, yes that was it. the throttle body must not have been on right. i took it back off and spent a lot of time getting it lined up and after that it ran fine.

also, i had difficulty removing the alternator. now that i have done it, to make it easier, i would do this: the alternator is held on by two bolts, the bolt closer to the passenger side screws into a bushing. loosen the bolt maybe a mm or two and hammer it inward to move that bushing towards the front of the car. if you move it a mm or two, it will make removal 100x easier.

hope this helps.

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Please, STILL can't find the answer to the question : On the 3.6L MKII engine, is there a bellows pipe that needs to be replaced? As stated, when you order the part number 996-107-175-50 as shown in the PET for part, "10", the bellows, you get a 90 degree bent oil hose pipe, instead. Pelican shows the part number for the bellows as 996-107-237-52, but lists it as '99 through '01 only. Yet the AOS is the same. Anyone that has done this, can you shed some light, please?!

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I did, and it did not come with one. Can I assume your car is older than 2002? On Rennlist, one poster stated that when he took the AOS off his 2002, there was no bellows, and the one he installed had none, and he installed it without one, and has had no issues for almost 6 months. But rather than get anecdotal information, I would really prefer something a bit more proven.

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I replaced my AOS, drove the car 8.5 miles without a flaw. Then it started pouring smoke out of the exhaust again and running rough. Any ideas?

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I replaced my AOS, drove the car 8.5 miles without a flaw. Then it started pouring smoke out of the exhaust again and running rough. Any ideas?

Yes, common occurrence, your old defective AOS probably deposited a bit of oil inside your intake system and it is starting to come out. You can either let it burn off (may take quite a bit of time, depending upon how much oil is in there), or pull the intake system off an clean it.

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