Guide lines for AOS- DIY replacement

If your AOS failed, what was the mileage on your car? I am considering a PM AOS replacement. My car shows none of the usuaL SIGNS associated with a failing AOS. My car is a 99 C2 with 76000 on the clock... Thanks.

Mine sprung a coolant leak because one of the plastic fittings became too brittle from age I assume. Mileage was @56,000. Luckily, I was only a few miles from home or it would have been another flatbed fiasco.

NO ONE on the board has had a failed Air Oil Separator fail on them??? I find that very hard to believe.

I elected to replace mine as PM while having my clutch replaced @ ~60K. The 15-year-old AOS was asymptomatic.

I had to replace my AOS. The plastic casing where the coolant runs through it cracked, so it was weeping coolant. I think my mileage was around 120,000 miles. I did not have the typical AOS symptoms, so technically it did not fail. It's a damn cheap piece of plastic that I wish someone would design/build a better system. It's a crankcase bleeder for crying out loud. Anyway, given the difficulty of AOS replacement (hated that job) I would wait until something happens to it versus PM. Unless the engine was out for some other reason. I know of a whole lot of other things I would preemptively replace if the engine was out as well.

Mine failed at 0 miles and 0 hr. I replaced the old one as a PM. The new one from Porsche failed out of the box (reading ~12" water vacuum. Normal is 4" water vacuum)! I got Sunset to warranty it. They sent me a new one. I pop that in and it's been working fine. So at the end I did the job twice and now I can do it under 4hrs. Trust me, you will not enjoy that job unless your engine is out. Lack of symptoms like squealing/coolant/oil leak/sooty tailpipe/blowing smoke/elevated oil consumption, etc, I will leave the AOS alone. Instead, I recommend getting a digital manometer digital manometer for ~$50 to monitor it if you're worried things go wrong silently. 0314151858 (Large).jpg

BTW, good that I had the manometer. I would not have caught the failed new AOS from Porsche right after the install, well at least maybe not before some time and damage is done. I have a habit of triple checking the new parts and my work. It paid off this time.

+996 I'm not touching it until the next clutch/IMS service.

Wonderful helpful replies so far. Thanks guys.

I did it about 3-4 years ago. I had never done anything that invasive to a car in my life. It required dropping the engine a bit and reaching into parts of the engine bay that took quite a bit of effort. But I got it done and thankfully it fixed the coolant leak that had sprung on it. The only thing I messed up on were the vacuum lines that required me taking it to the dealer to have them clean up my errors. The car still ran but not very well but they got it fixed for me pretty quickly. But if you need any hints or recommendations on what to do let me know and I'll try and remember some of the details. I think I have an old post out there describing what I did if you search.

Mine just failed at 54k. I caught it early, the rubber bladder inside the AOS cracked.

On earlier cars it's a lot easier. Once the transmission is out, it's pretty straight forward, but i would wait for a clutch job, or IMS, wouldn't touch it if it's good. 2002 and up they changed the location of the two mounting bolts. I did mine, and came close to weeping on few occasions. Had the transmission out but had to take the driver side intake manifold off as well and tackle it from the engine side. Still one of the bolts i tightened without ever being able to see it.

unless it's broke, don't fix it yet, unless you want to curse a lot.