rush3r

Hi guys,

I have a 997 S from 2004 with about 180.000 km (111 846 miles) which was always serviced at Porsche where it went recently.
Apparently it came with a loose oil cap and I got the CEL - went back to Porsche and they had the car for a couple of days to run some tests. They said everything was ok.

After about 600 km (400 miles) I was crusing in the motorway at 150km/h (93 mph), and without any notice and suddenly I got a huge smoke (it was by night but the smoke seemed black) from the back. There was oil comming out of the exhaust - I think it was just from the driver's side - and the car dropped all the oil. While I was stopping I did not notice any strange behavior on the engine (sound, power, etc)

I immediately stopped and the car was towed to Porsche (a different one).

At Porsche they don't have an official statement but they say it might be the AOS. I fear a scored cylinder or something more drastic ...

What do you think about the problem? Could it be caused (or boosted) by the loose oil cap?

Thanks in advance for the help!

stronbl

Sounds like you have the proper(?) folks looking at it ... my initial reaction from reading your post was to jump to the "it's an AOS issue" as well. Let's hope it is only an AOS and not something worse.

Good luck.

rush3r

I was just wondering about the correlation between the loose oil cap, the CEL, and this problem ... it was just 400 miles after, it's a lot of coincidence ...

Maybe the loose oil cap could increase the pressure in the AOS which could then lead to the failure ... or not?

Petza914

That description is definitely AOS related. Usually, one of the tests for a bad AOS is to see if you can remove the oil cap with the motor running. If it's locked on due to vacuum, the AOS is likely bad. Seems like, if that's the test, driving with a loose oil cap could allow for too much air being sucked in and possible damage to the AOS. If replacing the AOS and you haven't replaced the starter cable on this early production '05 997, then you might want to do that cable replacement too which will prevent the hot no-start issue that can occur from bad factory crimps on that cable.

Macster

Just a coincidence the AOS failed -- which is what it reads like -- and the oil cap was removed.

I've left the oil cap off a few times on my Boxster and the AOS lasted anywhere from 80K to 120K miles.

More recently the cap was leaking bad enough to trigger a CEL. Eventually diagnosed the leaking cap and replaced it. The AOS failed but tens of thousands of miles later. The leaking cap did not play a role in the AOS failure.

Ben Z

If it turns out to be the AOS and you have it replaced, be sure they also replace the tube/hoses connected to it. On my '05 the large, ribbed plastic tube was brittle from age and heat...looked fine but leaked vacuum.