Oily AOS tubes: Should I be worried?

Hi all, Recently was in the engine doing an air filter change when I noticed that some of the lines connecting to the AOS seem oily. They weren't dripping and I couldn't see any pooling of oil, but they were noticeably moister than the surrounding plastics. Lately I've also had sporadic smoke on startup (which I've chalked up to flat six quirks) and a rhythmic ticking that corresponds to engine RPM when I coast (which I attributed to the fuel injectors being noisy) but now I'm wondering if I've misdiagnosed those and they actually indicate an unhealthy AOS. As in, the ticks are lifter noises and the smoke is from bypass. This is also the first time I've opened the engine bay as I've only owned the car about 6 months after buying it second hand, so I'm not sure if the hoses were simply oily before and nobody cleaned them, or if they're fresh. Is a bit of oil on the AOS tubes normal, or should I look into replacing this part? Pic included. Thanks in advance!

Boxster . Base 2.7? Or S? Mileage? Sent from my SM-G988U using Tapatalk

Smoke at at startup is normal. Trust me you'll know when the AOS is dead, my 986 looked like I was mosquito fogging.

If I had to guess, that looks like a leaking o-ring at the hose connection to the AOS.

Thanks all for the replies. To answer some questions: Boxster S, 3.2L (2005) Mileage: 126400 mi Good to know nothing is an emergency. I'll take a look at the o-ring connecting to the AOS next time I've in the bay. That being said, even if the AOS hasn't yet failed (no mosquito fogs) should I be wary of this being an indicator of bad health? If it's on its way out then I'd rather replace it now than have to replace it plus plugs plus o2 sensors down the line when it blows.

If you are a DIY'er, then changing the AOS as a preventive maintenance task makes a lot of sense to ME. Especially on a high mileage car that it might not be known the history. And from what I gather, they can go out all at once, or they can give signs beforehand. Although a little exhaust smoke is NOT unusual at coldstart, even for the healthiest flat6, the symptoms of a degraded AOS can overlap with what is normal, so how would I know for sure? I really don't want that mess on my hands that a failure can leave me with. I also understand that it is imperative to use an OEM part, rather than saving a few bucks. Sent from my SM-G988U using Tapatalk

You should see a rotary with a bad oil seal…. Omg..

In my case, I have no symptoms of AOS failing yet, but with 105K kms and 14 years I'm doing the preemptive replacement at an indy mechanic this week. Also doing water pump, thermostat and serpentine belt. With all the solo driving I do in areas with no cell coverage, preemptive replacement of failure-prone parts is a wise move, methinks.

I did my spark plugs at 13,000. Why? Because they had been in the heads nine years and my internet reading paranoia convinced me there was a chance they could seize. They all came out and went in like butter, was it a waste of money? Maybe but now I know there is no issue with said plugs and that makes me happy. Big fan of preventative maintenance. In my previous position A LOT of imaging chain problems were simply poor maintenance. I drove a few hours one time to discover the entire problem was not washing rare Earth screens meant to be washed each quarter year at the minimum. It did not escape my notice that machines thirty years old were often perfect, all that was necessary was a diligent field engineer.

Good call. I’ve read a lot on plugs seizing in our cars too. Shawn in VA (USA)

Great takes by everyone. I'll start slowly assembling the parts needed to do the maintenance. Thanks everyone for the contribution!

AOS is a fairly easy replacement IF you have the right length pliers to get the bottom hose clamp undone. And be careful with the squeeze connector for on the corrugated lines. They are easy to snap off. Part isn’t too expensive. Take the opportunity to clean your engine bay if you are OCD like me. The 987 is a dusty engine environment.

Racer, I had more than a decade of wrenching under my belt when I did my 986 AOS and IMO that polymer tube clamp is nonsense and quite easy to damage. If I had to do one again I'd certainly collect opinions on that part of the job because IIRC that clamp nearly broke with little to no effort it was like a snap fit. Screw that, give me a hose clamp and a bleeping hose, why that is engineered the way it is remains a mystery to me. I also remember having the car jacked up and that access from below and above made the job easier.

Lol That RD400 smoke smelled WAY better than our Porsche smoke. I'm just saying. Sent from my SM-G988U using Tapatalk

Smoky oil in the AOS vacuum lines can have negative effects if not diagnosed properly. First, check you air filter for back flow of oily smoke. then check the mass air flow meter. There is a spray that works well to remove the oil from the mass air flow meter. Question is where is the AOS sucking that the oil from? Is it the crankcase or the heads as both have leads to the AOS. If its the crankcase, then you might have an issue namely, a small amount of bore scoring. Another item to look at is the injectors, as they may be slightly fouled. This could add to the blowby as fouled injectors certainly could cause that cylinder to have bore scoring over time as raw gas is not a lubricant. For the injectors a can of injector clearer every 3rd tank should help. Replace the AOS and check for oil in those lines after about 6 months. Always keep an eye on the exhaust smoke at start up and the inside of the exhaust pipe to make sure the residue is not increasing. The 987.1 AOS is fragile in that they can easily be overwhelmed by oil from the sump or even oil from the heads. Our engines only have 1 head oil pump to the sump, while the 9A1 engines have 2 for each head. The AOS sucks the extra oil out of the heads that the single oil pump can not pump, This usually happens in high G loaded events. So if you do not use grippy race tires and are not sliding your car around in long high G corners, the oil situation should go away once the new AOS is installed. And as I mention earlier, add a can of injector cleaner every 3rd tank of gas for a couple of months. Check you oil filter after each change to see if your filter as captured either magnetic or non magnetic metal like flakes. If no particles, then most likely the new AOS will be the cure to your oily vacuum lines. If you have flakes, then check out Jake Raby flat 6 innovations video series on bore scoring. If you have questions, let us know. Also know that some oils vaporize at a higher rate than others call NOACK score. The lower the score the less smokey oil in your going from your AOS to the induction system. Also oil AOS can actually cause oil droplet to form and be suck through these lines to the combustion chambers. Luckily it has gas to mix with in our port injected engines. The direct injected engines when we see this type of oil in these AOS lines cause the intake valve to carbon up.

Thanks for the in-depth writeup, super informative. Recently did the air filter, no oil. Last time I did the oil change, sent the oil over to Blackstone labs and they found it to be nominal, no metallic particles or weird composition. Cut open the filter too, no metallic particles. Not too worried about bore score because of the lack of symptoms and my older M96 engine (2005 987). Will definitely start adding techron every once in awhile and I've queued up the AOS replacement for a weekend I have time. Again, gents, appreciate all the comments and chatter. Super helpful for a newbie p-car owner like myself.