Hello All,

2005 Carrera S
72K Miles
All scheduled maint Done

As I was leaving work, I noticed the car was idling rough to the point it was stalling. This never happened before. It finally smoothed out, so I drove it home with no issues. I pulled into the garage at home and pop the rear decklid. I noticed a loud strong hissing sound. When this sound was heard, the oil tube would be sucked down and the engine would stall. I took a video of this to let you see what I am referring to.

Here is a link to the video.



After some searching on this forum, i suspect its the AOS going bad. Do you guys agree? I want to make sure of the issues before it goes to the dealership. Car shows no sigh of smoke. when I take the oil cap off, there is huge vacuum. Any advice is appreciated. Many Thanks.

 

When the separator fails, you will begin to see a large increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system is not healthy for the engine and it can foul spark plugs and destroy catalytic converters at the very least. The failure of the air-oil separator is often but not always, accompanied by huge amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as the oil being drawn into the intake can affect the mixture level. The oil cap may be very difficult to remove when the engine is running due to high vacuum levels. In addition, you may hear a high-pitched squeal from the engine when it's running because air is being sucked in past the crankcase seal due to the extreme vacuum inside the case.

 

Thanks MYC2SPC, I have not experience any of the smoking or squealing you mentioned above. I was curious to see if maybe this was a early symptom to a failing AOS. The hissing noise is very loud when standing outside. I believe that the hissing is air getting pulled in by vacuum and not air being pushed. I was hoping that someone may have experienced or seen this somewhere before. I know that the AOS is a part that can fail over time, so I wanted to be preventative when I can.