5CHN3LL

AOS is the air/oil separator. It's the Porsche equivalent of a $2 PCV valve - but much larger, more expensive, and difficult to replace.

I wholeheartedly disagree with buying a car that has already had some kind of IMS retrofit. Buy the cleanest, least molested (i.e. as close to bone stock as possible) and do with it what you want. There are two reasons to do the IMS retrofit: preventive maintenance and in response to a failing or failed bearing - and sellers don't have any problem claiming it was done as PM regardless of whether or not it's true.

craig001

http://www.autofarm.co.uk/pdf/Total911_July06.pdf

http://www.pistonheads.com/features/...ng-guide/30277

http://www.ferdinandmagazine.com/por...1-buyers-guide

http://www.autocar.co.uk/car-news/mo...d-buyers-guide

http://www.revolution-porsche.co.uk/...rs-guide-look/

https://rennlist.com/forums/996-foru...ing-guide.html

Porschedane

Thanks Slacker for the explanation of the AOS. And I agree with you on the IMS do it while the car is yours because then you know!

Slakker

What he said. The AOS goes bad, mixes coolant with the oil, and causes catastrophic engine failure. (Search for intermix)

There are a lot of different opinions on these engines and a lot of people that know way more than I do. But Flat Six Innovations recommended to me to change the water pump and AOS every 3 years, regardless of mileage and my retrofit IMS every 5 years or 70k miles. There are plenty of people that don't agree with this but none of them seem to have anywhere near the experience that FSI has. So while I'm learning something, I try and figure out who the smartest person I can find is (and they are brilliant) and then just do what they tell me until proven otherwise.

DoubleNutz

That's an interesting thought 5CHN3LL... I'd like to learn more about why you suggest this. Simply for expanding my worldview and own eye-opening edification.

gnat

There have been cases of people finding out their bearing was failing, slapping in a retrofit, and then pawning it off on a sucker (via CarMax is the most popular option).

If the swap wasn't done by a shop the buyer can trust then you just don't know the state the motor is in and going in and proactively changing it anyway might not make it clear.

I would amend Schnelly's view to include retrofits done by certified installers as being OK too.

DoubleNutz

Ahhhhh, IC... those are indeed reasonable arguments, I have never considered.

OK thanks for the heads-up view there. Something to consider and look deeper into when conducting a PM for both myself and on behalf of others.

gnat

In fact there was a recent thread of a bearing failure where the new owner had a receipt for a bearing that was never installed. It was not a case of an intentional screwing, but highlights the unknowns of someone else doing the swap.

DoubleNutz

WOW!!! That's just jack'd up... for real!

porsche951

Read this www.imsretrofit.com

DoubleNutz

Thanks for the link share...

I actually read that on LN's site years ago before I had my IMS replaced... not that I needed it but I had a thrust bearing liberate itself and when I replaced my engine I had the IMS replaced (by a qualified indy). The IMS I removed was in perfect condition, but I chose to have LN's put in anyway, in addition to Jakes IMS Guardian.

I should mention that my 996 frame has 140k on the clock and the replacement M96 powerplant a bit less than 50K

Ahsai

Just fyi, that site has been updated recently.

Ahsai

I mean this one
http://imsretrofit.com/ims-101/