AOS - Source of repeated failure?

Any thoughts as to why an AOS can fail?

My 2002 Base tip with 148K miles showed a check engine light. I took it to a local indy and they indicated it was an AOS failure. I had replaced the AOS two years ago, and about three months ago after it failed, I had it replaced at the dealership.

Any thoughts on why the AOS would be going out so soon?

Thanks,
BarryL
2002 base tip
148K miles

Quote
BarryL
Any thoughts as to why an AOS can fail?

My 2002 Base tip with 148K miles showed a check engine light. I took it to a local indy and they indicated it was an AOS failure. I had replaced the AOS two years ago, and about three months ago after it failed, I had it replaced at the dealership.

Any thoughts on why the AOS would be going out so soon?

Thanks,
BarryL
2002 base tip
148K miles

is just crap.

The AOS can last 80K miles or 100K miles or even more miles (I can't recall off hand how many miles the current AOS has been in service), but they can last fewer miles.

If they last too few miles, or too brief a time, it can be just a bad out of the box AOS, which is what it reads like you have.

BTW, the dealer should have provided a 2 years parts warranty on the AOS so you might have qualified to have this replaced under warranty had you taken the car back to the dealer.

Anyhow, I cut one bad AOS apart and found the rubber/fabric reinforced diaphragm had developed a crack/split which routed intake vacuum directly to the crankcase with little or erratic control of the amount of vacuum.

Sincerely,

MarcW.

You have what amounts to a still, with a rubber/plastic diaphragm, which degrades. If even a small amount of oil passes, you get a smoke bomb, and oil into the cats, which degrades a very expensive part. Its nto sufficiently robust.

Now to the empirical part. My car is driven very hard. Track days, autoX days, etc. Mine lasted about 40k and was very early in its death spiral when i replaced it. Under normal circumstances it might have gone 60-80k. Since this is typical, i assume you just have to consider it a maint part with a 60-80k interval.

For the record, its inconvenient, but you can do it yourself, with jack stands, and a remote-operable pair of hose clamp pliers ($45 for a nice set form SEARS)

Grant
(now with much bigger worries to contend with)

Grant

gee-lenahan-at-gee-mail-dot-com

Tomorrow I take it into the dealer who did the AOS a little over 3 months ago and about 9K miles.

So the first AOS lasted approx 70K miles (I had IMS failure and replacement engine at 39K, new AOS) , the next one about 40k, and the last one about 9K. Hopefully I'll have better luck on the next one.

I'll post the details on resolution.

Thanks Marc and Grant!

Barry

If memory services me (it rarely does), some one posted here quite a while back about saving money on replacing the AOS if you DIY. It is an expensive part, $500+ or so, but the writer here said that you can get an identical part that is in VWs or Audis', don't recall which, for about half the price.

Having said that, I could be thinking of a totally different part! But, if this is right, it can save folks some money.

... the AOS is a relatively inexpensive part (about $100).
The MotorSport version used for racing and heavy track use is about $500, but is not a drop-in part and needs modifications in the engine bay for it to fit.
Make sure that the tech is using an OEM Porsche AOS.
There are at least three Chinese knock offs which sell for about $50 and are a piece of (expletive).
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

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Grant

gee-lenahan-at-gee-mail-dot-com

FYI Pedro...I just bought an 94.00 supposedly genuine OEM Porsche AOS from a big retailer "Partscontainer" on ebay..however, it looked suspect due to the packaging. It was in ziplock bag with a USPS box. I don't think Porsche would sell parts loose like that. Anyway, I did some comparisons to the Chinese ones on Alibaba, they look identical to the supposed genuine one, except the part that says MKO Germany is left blank on the Chinese ones,?Now to be fair I found pics of a few genuine ones in Porsche boxes on the Internet and they also looked very similar to the one I received, so I can't give a definitive answer. Moral of the story you have to be careful. I won't ever be sure if the part sent was a knock off or genuine but I rather not take a chance to save 20 bucks and have to tear it out in 6 months.

The motorsports unit is $750.00 Maybe that's what you heard about.

Mots Audis use a regular old PCV valve

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I was pleasantly surprised but the dealer Stevens Creek Porsche took it back no questions asked and replaced the AOS. The service rep told me that it is rare to have the AOS last such a short time, but that he has heard of the clamp holding the flex hose cutting into the hose.

Interesting that when I had taken it in back in May and told the rep I had replaced the AOS myself a year and a half earlier, he made a passing comment in fun that maybe I had "pooched" the install. I didn't come back this time with, "I guess you guys pooched the install" after their install lasting just 3 months. I was just happy to have it replaced at no cost.

Hopefully there is not underlying reason for two consecutive premature failures.