theprf

No.

2fcknfst

AOS is a new term, what's the meaning?

T10Chris

Air Oil Separator

2fcknfst

I see... thought that was only a diesel thing.

theprf

The Air Oil Separator is one of the functions of the dry sump tank. The AOS device in the NA cars is notorious for letting the intake fill with pooled oil then sending oil slugs into the cylinders, sometimes enough oil to hydrolock the engine.

2fcknfst

That doesn't sound pleasant; so, an emissions type thig, like in a diesel?

T10Chris

Yeah, it is emissions related with blowby gases and sending them back through combustion again.. What (usuallly) happens when it fails on M96/M97 is excessive vacuum gets applied to the crankcase and that vacuum draws oil into the intake system where it then goes into combustion chamber....

2fcknfst

I thought those things were supposed to be valved so you couldn't suck anything but oil vapor?

Defeatable?

T10Chris

Sure that is how they work when they work properly, but that is the part of it that fails. The reality is they fail in varying degrees in those cars, rarely catastrophic at once. The valve starts sticking a little more, then a little more, you start noticing more smoke, misfires, get CELs for fuel trims, cloud behind the car starts to look like a mosquito spray truck when driving, etc.

I'm not positive of a reliable defeat process, never really looked into it. I don't have near the experience on those as I do on Turbos and GT3s. I will say probably could figure something out.

2fcknfst

Thank you... The reason I ask is because I currently have @sdematt Carrera and will be driving it up the valley this weekend and it would suck (no pun intended) if something like that happened.

Bernard IV

Is the turbo seal the metal area the shaft rides on or is there a rubber seal in there? Never taken one apart.

theprf

Usually turbo seals are graphite or ceramic instead of rubber, and they ride on specially machined surfaces of either the pinwheels or washers that are under the pinwheels.
I have not changed any on these KKK turbos. I changed a set of the truck sized IHI turbo on my Dad's Turbo T-Bird way back in the day.
Strangely the Mitsubishi turbos on the Cayenne do not ever seem to have oil seal leaks. Perhaps because they are water-cooled.

sdematt

I have the upgraded Air-Oil Separator (UAOS) as per: The 996/997 Ultimate AOS UAOS-AL Complete Kit (lnengineering.com)

I don't have the track drain installed (which means you never have to empty it), but it should throw a light if it does need to be emptied. I think it trips the coolant sensor?

2fcknfst

I did not know that... if anything happens, I'll let you know.

996TS

Have a look inside the lower intercooler pipes, could be full of oil