AOS time

After years of following this forum and taking note of many threads involving the ubiquitous AOS failure, and the ensuing replacement, my number was pulled today. I always subconsciously give half a glance in the rear view mirror when starting my ‘08 Boxster in my garage, and the absence of the puff of white smoke has been heartening. Until today. After starting and while buckling my seat belt, out of the corner of my eye I caught a glimpse of white smoke. Is. That. My. Car? And I had just completed service and maintenance items during the cool weather here in Southern Florida, before the heat index ramps up over 100°. Unfortunately, I missed that window with this unexpected problem as it was 94° already today. Next step is ordering the part. Are these all about the same quality, or should I avoid shopping price over brand name? What component actually fails inside the AOS? Or is it just a buildup of oil film over time and miles? And is it recommended to replace all the ‘plumbing’ attached to the AOS? Seems like I’ve read about a lot of those replacing the AOS discover brittle, cracking tubing. And if it isn’t cracked or broken it ends up breaking during disassembly. Anyone who has been through this, I welcome your input.

My friend (2008 987BS) replaced his last year and he said the diaphragm inside can crack / tear over time - his was fine and it was preventative. He didn't replace his hoses / tubes though as his hose / tubing were "fine"

I used the Porsche part when I replaced mine. It’s not very expensive but it’s a fair amount of work so in my mind it wasn’t worth taking a risk.

About that smoke...has it been present for multiple starts? Had the previous time been very short duration, like moving out of the garage to wash the car? If so, it is not AOS smoke, just water vapor.

If you feel better about OEM parts, and are a PCA member, you can get a 10% discount from your favorite dealer (you have to ask for it, though). Some of the hoses get brittle from age/heat, and every car seems to be different. Just don't "muscle" them off and you should be fine. Good luck, Steve

I went with a Factory Porsche . Got it from Pelican Parts because of the warranty. FCP Euro also has the warranty. Did not replace the plastic hoses. Some of the hose connectors were hard to remove had to twist and pull. Had to buy an inside out star socket to remove the AOS unit. Not very hard to do. Bernie

It's not too difficult on 987.2 but I think .1s are a little more tedious to DIY. What year is yours? I have instructions somewhere from when I did my .2 but its a very different process between the half gens. I went with the Porsche part from Pelican.

It literally just appeared the other day. First time I ever noticed it. And it was after the car sat for a few days. I’m figuring it wasn’t water vapor because it seemed to hang in the air in the garage, almost like someone had just exhaled a cigarette or something. I would guess water vapor would dissipate quicker than that, but I will monitor for the next several starts over a week or so and see if it was an intermittent sighting. If it persists, then I will proceed to replace it.

Mine is an ‘08, thus the 987.1

An occasional puff of smoke on startup isn't a real cause for concern on any horizontally opposed (boxer) engines. Unlike every other sort of engine, oil can sit in the bore at the lowest level and if the ring gaps line up - it can be sucked into the cylinder on startup, and you get smoke. Once the engine is running, the rings start spinning and no more smoke. The BMW "K" bike engines, a horizontal in-line 3 and 4, were known for doing this (I owned several). There was a simple trick to avoid the smoke. Lean the bike so the oil drains out of the cylinder and back into the sump. BMW in a fit of brilliance, put the intake/valves/cylinder head on the left side, and when the bike was on the sidestand, that was the low side. BMW eventually pinned the oil control ring so the gap couldn't end up at the low point, and that solved the problem. If it isn't repeated - I'd foregddaboutit.. (my '09 has done this maybe 3x in 35k miles..)

This information is helpful. This is, literally, the first and only instance of any smoke. And it was very light and fleeting, not the mosquito fog truck type of emission. Hopefully it was a one-off. But I will be monitoring it and watching closely for any recurrence.

Replace your drive belt "while you're in there". You may want to think about your water pump and thermostat as well. It's all basically the same work, no sense in paying the same labor twice.

Caveat - My car is a 987.2 CS I broke a vacuum line while I was in there doing the AOS. After replacing it, I am getting better fuel mileage. I think I had a vacuum leak before and just didn't realize it. The hard plastic vacuum line runs into standard rubber "fuel line" style hose. You can buy specially bent pieces from Porsche for too much, but you don't actually need any of those fancy bends. I just bought some silicone vacuum tubing from Amazon. - I also broke the nipples on the intake manifold vacuum solenoid. I am pretty positive this is a different part for your car. If you are careful, this might not be a problem for you. vacuum line - you only need 1-2 meter. If you are in the STL area, you can have all the extra I bought. https://www.pelicanparts.com/More_Info/00004320501.htm?pn=000-043-205-01-OEM&bc=c&SVSVSI=3418 silicone vacuum hose Amazon.com: Boost Monkey Silicone Vacuum Hose, 3.5mm Inner Diameter, 10 Foot Length, compatible with VW AUDI Part N0202821 (Black) : Automotive Buy Boost Monkey Silicone Vacuum Hose, 3.5mm Inner Diameter, 10 Foot Length, compatible with VW AUDI Part N0202821 (Black): Vacuum - Amazon.com ✓ FREE DELIVERY possible on eligible purchases www.amazon.com solenoid for 987.2 as example only, not for your car https://www.pelicanparts.com/More_Info/0PB129061.htm?pn=0PB-129-061-OEM&srsltid=AfmBOoout31Vw6UiKWxj9G7EQfS9Xnc7WWBz5N41FnZI35AQPEFAAlUm If you don't break the solenoid, don't replace it. I do recommend replacing the cheap vacuum lines. Also, the vacuum lines all meet under your plenum. Plan to pull your plenum so you can clean it out. Mine had a decent amount of oil built up in it. Final tip. If you remove the throttle body and hoses to do additional oil cleanup, don't forget to plug the wiring harness back in. That was embarrassing to sit in my driveway, push the go pedal, and have the engine just keep idling while the dashboard lights up like a christmas tree.

Good suggestion, no sense going back in there again, but luckily I had done the water pump, t-stat, serpentine belt and coolant temperature sensor about a year and a half ago. And if I’m lucky, I may not even need to do the AOS after all. I haven’t witnessed the puff of smoke during the last few starts, yesterday being my local chapter’s Porsche and Pancakes breakfast and I did some stop and go starts while heading there and returning, stopping along the oceanfront several times to take in the views. Possibly, as deilenberger suggested, it may have been the piston rings lining up which may have caused it. But I will monitoring it going forward.

Yup. Sorry for the delayed reply here. I bet you're just fine. @deilenberger is totally right. I've had on/off puffs of major smoke during these trips, before and after. Often depends on the angle of the car and how I park it overnight; it's totally not a temperature thing for me. FWIW, my smoke been too bad on this current Road Feast road trip. If you want, Chuck, park it overnight and I can leave early and meet you at your house before you start it up and watch it while you start it up cold. Should be early this week that I'm leaving, and will be in touch with you for details. Happy to help if I can.

I had my AOS replaced last November before putting it into storage and now that it is out, I do get some "smoke" on start ups but not the dense kind from when the AOS failure, so probably (hoping?!) it's just cooler morning starts and water vapour buring off. PRobably last a few minutes but definitely gone by the time i reach my destination and I cannot recall seeing any whilst driving along. In the coming weeks/month, I will plan to get the water pump, serpentine belt and possibly pulleys replaced as required...based on shop feedback.

Chuck, you can check the integrity of the AOS using a vacuum gauge, on top of the oil filler cap. (I did it, using instructions from JFP in PA on the 986forum) if you want I can dig my manometer and share a couple of pics. IF, you have to replace the AOS, I would strongly suggest two things: 1) Buy a spring clamp tool and 2) but the two AOS 'accordion hoses' as these get very hard and yours are at least 17-20 years old.. PS: replacing the longer one from the AOS to the top of the bank 4-6 head, you don't have to remove the plennum as you can access the hose by removing the inspection cover behind the seats. Read the post No.2 http://986forum.com/forums/performance-technical-chat/77296-new-aos-same-problem-2.html