996 3.6 - smoke from both exhausts. A head-scratcher!

[maturin23]

Hi all

I have a 2003 3.6 C2 - recently started smoking from both exhausts on start-up. After a few minutes the oil burns off and all is fine.

I had the AOS swapped a couple of weeks, but the problem only briefly improved.

I've just had leak down/pressure tests done plus a scope into every bore.
The cylinder integrity is excellent and there's no sign of any wear to the bores.

Everything points to it being a faulty AOS but the one fitted a couple of weeks ago was a genuine new Porsche part. There's also not quite as much oil build-up in the inlet manifold as might be expected.

We are scratching our heads as to whether it could be some other element of the crankcase 'rebreathing' system.

Given that:
- oil is definitely reaching the combustion chambers on both sides
- there is zero sign of integrity issues in the cylinders or head

Is there anything else it could be other than the new AOS?

Thanks in advance
Ian

[maturin23]

Thanks Cmoose - some oil in the induction/intake system but I honestly don't think it's residual from the prior failure.

I cross-posted my question to Rennsport - a faulty new AOS isn't completely unheard of. Might have to bite the bullet and have a new one fitted on that assumption.

I was hoping there may be another point of failure other than the AOS diaphragm where oil can be pulled into the intake flow but looks like there isn't.

[skinny]

Valve seals?

Isn't there a vacuum test you can do to look at whether the AOS is looking ok or not?

[cd1957]

Hi If you still have the old AOS, carefully cut out diaphragm to see if its actually split.

If the new one is faulty you can take car straight to dealer, all parts have 2 year parts/labour warranty, subject to correct installation,was manifold cleaned out.

I have just replaced 997 3.8 one, cleaned out manifold, but loads of oil in bores, ran it for 3 hours outside in wind before it cleared.

Chris

[maturin23]

Sorry chaps - a bit late in updating this one.

Turns out it must have been an oil overfill when they fitted the AOS - after a few days of some start-up smoke (but gradually reducing in volume) the car is now clean as a whistle, even after being parked up for 3 days.

Relieved and slightly cross at the same time.