Shawn Stanford

Hi all. I just replaced the AOS in my daughter's 01 and I thought I'd share the experience.

The symptom was a good-size puddle of oil under the car. My mechanic diagnosed the AOS and while overpressure in the crank isn't the common symptom of AOS failure (normal symptoms are clouds of white smoke on start up and excess suction in the crank), it is a possible symptom of a bad AOS. The AOS was only around $100. I checked out a couple of videos on Youtube, and I found Burner's to be the most informative.

Burner went in from the top, but I found another video from TrackHabit where he in from the wheel well.

I got the AOS in the mail and pulled the engine cover and the right rear wheel. Between looking down and looking up and comparing that to what I had in my hand, I could get a good picture of what I would have to do. I realized that I wouldn't be able to go in from the top for all of it.

I took off the topmost hose connector, then I struggled with the lower middle hose connector, which was sticky. I got it after much struggling and some WD-40. It was mostly a leverage problem, as there is a good-size rubber hose running through the area. I realized later that I could have squeezed the connector with one hand and pushed against the curve of the hose with the other, and that probably would have freed it relatively quickly and easily.

At this point I moved to the wheel well. I had to sit on the floor more-or-less in the wheel well and reach my arm over the drive shaft and through the gap next to the motor. I couldn't look and touch at the same time, nor could I get more than one arm in there at a time. So it was a matter of looking, then reaching in to do things by feel. It was actually easier than it sounds.

The rubber hose at the bottom of the AOS was held on with a jubilee clip, which is non-OEM. So, the AOS in this car has been done before. I read several narratives that suggested using a jubilee clip was better than an OEM-style hose clamp because it was easier to remove later on. I got a small socket on the nut and the clip and the hose came off easily enough. I then loosened the two bolts holding the AOS to the motor (still from the wheel well), and then I pulled the AOS out from the top.

The tube at the top running into the intake had a light film of oil, (it shouldn't, that's the entire job of the AOS), and the middle tube of the AOS had a thick rind of goopy, tan oil sludge. Clearly the AOS had failed.

Installation was the reverse of removal. I maneuvered the new AOS into position from the top. It took a couple tries to get it oriented correctly so that the bolts were lined up with the mounting holes. I got the bolts started by hand, then got a small socket in there to tighten them down. I had already sprayed the end of the hose with WD-40 and put on the jubilee clip. I pushed the end of the hose onto the pipe and pulled the jubilee clip into position, and the fun started.

No, seriously, it took me three tries to tighten down that jubilee clip. I tried it twice with a small socket, but at some point the clip slid off the end of the pipe and I had to back up and restart. I finally got it snug enough turning the socket in my fingertips that it didn't slip off when I tightened it with the socket wrench. All of this working by feel!

After the rubber hose was on, I went back to the top and the other two plastic hoses went on in less than a minute.

I fired up the car and let it run for 10 or 15 minutes, and everything seemed okay. I turned off the car and no oil. I buttoned everything back up and gave the keys back to my daughter and the puddle is gone. Success!

This required almost no tools. Just what was needed to get the car off the ground and a wheel off, and a couple of small metric sockets. The car doesn't need to be high, and I think it's easier if the car is low enough to get at the top and bottom at the same time. It's pretty fiddly, but doable by the average DIYer. I asked my indy - who is exceptionally fair in his pricing - and he quoted me four hours for this repair. My actual 'hands on' time was about two hours, with an additional two hours of research, prep, and stopping to answer the phone or think about what the hell I was doing.

I think if I had to do it again, I could probably do it in less than an hour, all up.

TTGator

Man after my own heart with the DIYs. Thanks! I'm sure this will come in very handy one day!

Brian in Tucson

Burners vid is pretty good as usual, But for most of us, going in from the top isn't too doable. I need to do mine, My car has spent the winter on jackstands waiting for a new AOS. I've been sick for months it seems like.

Thanks for the excellent write up Shawn! I'll buy you lunch and a bottle of Jack if you come over and do mine!

Shawn Stanford

Throw in a plane ticket and you've got yourself a deal.

Brian in Tucson

I'm almost ready. Mine is a porsche reman'd. They used those star drive fasteners and they seem to be super tight. Got one off, the other is being stubborn Dammit, I wish I'd done this when the engine was out and sittin on the carport floor.

Brian in Tucson

Update. Nothing would grip the upper star drive bolt well enough to loosen it. I finally gave up and used the big long handle for my motorcycle lift and pried on it til it broke. Came out pretty easy then. And I could get to the star drive bolt with an 8mm socket. The way is clear to install the new one. Not going to reuse the star drive bolts, I think!

Brian in Tucson

New update. Mine was probably the original from the factory rebuild. They used a spring clamp on the bellows/hose. This whole operation is pretty hellish IMHO. Getting to that spring clamp is no less awful. When I broke the top mount on the old AOS, and it was flopping around, I just pulled the unit with bellows out of the fitting on the block. The new AOS comes with a new bellows so that even if I shredded the old one it would be no loss. It came off easy with the spring clamp. I have a new spring clamp with the light blue applicator as shown in the second video of Shawn's write-up It's just a matter of positioning the clamp and applicator so I can grab and pull. Looks to me like using a screw clamp is more trouble than it's worth..

bekks

Anyone who is considering doing their AOS and also considering a clutch/RMS/IMS, do them at the same time. Just changed my AOS with my transmission out and it was simple.

Shawn Stanford

My daughter generally drives the car to and from school during the week, which is about a mile, so I wasn't 100% that the AOS had cured the oil leak. However, I took the car on a trip of over 100 miles yesterday, and it's dry as a bone.

Quadcammer

maybe just me, but I find this job not very difficult. The only pains are the lower hose pinch clamp and the lower hose clamp. Even then, with the wheel off, access is very good.

Brian in Tucson

I found getting those two bolts to be a real bitch. On a tiptronic car,there's a lot more stuff in the way in that corner. Porsche used those stupid star drive bolts, which I had a real hard time getting out even with the proper tool. OTOH, it's all plastic, and what it attaches to is all cast aluminum--and it's being replaced, so there's no need to try to preserve the old AOS. Maybe it will be easier next time?

Brian in Tucson

Like a lot of what Porsche does, it's a complicated solution to a simple problem. The AOS is Porsche's answer to a PCV valve. If I were smarter, I'd probably try to figure out a PCV system. Cheap and effective.

It's like the vacuum lines and switches all over the top of the engine, but under the plenum. If you brush against one and it comes loose, you have to take the mid plenum out to find the correct connection (don't ask me how I know.)

Brian in Tucson

You kinda have that backwards, if you have your trans lowered, it's a great time to do the RMS, AOS, and IMS bearing. Whether they need fixing or not.

Bbiela

Thanks for posting! Mine just went out yesterday at a DE event and it'll be my project next weekend.

joseph mitro

I think that's what he was saying....