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

Cuda911

Did you maybe overfill the oil?

Ahsai

Yes, put a manometer on the oil filler cap to measure the crankcase vacuum at idle, fully warmed up. You should get 4~5 inches of water. If you get 8" or more, most likely your AOS is bad and yes, a brand new AOS can be DOA. Happened to me.

When the AOS was replaced, did you check the intake manifold deep inside where it branches off to the 3 cylinders? That flat area can hold 1/2qt of oil!

maturin23

No - the oil hasn't been overfilled (actually hasn't needed topping up since the last service).

The car is actually with my local specialist, but I'll make the suggestion!

dgjks6

When i had my 3.4 rebuilt, I had a new AOS put on. It failed immediately and had to have another on put on. I had the second one put on at the dealer. I asked of there was a problem with the engine that caused the second to fail and the response was no - just got a bad one. Put 30K miles on after that without a problem.

Imo000

Nothing pi$$es off a mechanic more than when the owner comes in with a list of "suggestions" they dug up from the interwebs! Let him/her do their job.

Hurdigurdiman

**** pissing the mechanic off I say. Better for him to be pissed off because he was never told in the first place. Some 'so called mechanics' need to be told and pissed off anyway.

maturin23

AOS has been blanked off, still minor smoking from both pipes

Oil was slightly over filled (by about 1l) but that not enough to cause issues.

Leak test is next to eliminate ovalled bores.

Southern Man

"Oil was slightly over filled (by about 1l) but that not enough to cause issues."

I think you may want to rethink this. I used to have occasional smoking on startup, even after AOS was replaced. I always maintained my oil level at the full mark, but after reading on here it should be about halfway on the stick, I started using that as a guide a no more smoking at startup.

Ahsai

^ Great advice.

1L is gross overfill considering between min and max is only 1.25L.

Imo000

The car is at the local specialist, he doesn't need to be told what to do if he is a 996 specialist. If he does, take the car to someone that doesn't need our feedback.

Do you bring a list of "suggestions" to your surgeon?

rattlsnak

My did the same thing until I lowered the oil level down to half way down the dipstick. And then it took a few weeks to 'burn off' the rest before it stopped smoking.

extanker

this kinda made me laugh
many years ago lying on a stretcher waiting for my number the doctor gets ready to give me an injection and i ask/suggest he put it in the IV T line . With a "hey thats a good idea " look he did..............i told him that i thought i had enough holes in me that day.

TonyTwoBags

^^been there & solved the issue by draining a bit of oil & keeping it near the halfway mark.

+1, plus it's the cheapest possible solution!