2004 3.2L Cayenne Vacuum Leak
 

I have a large volume vacuum leak in my valve cover. I have replaced the crankcase ventilation/AOS with a new one. When I disconnect the valve cover side hose on the AOS I still have vacuum in the hose and no vacuum in the valve cover. Is there something else I am missing? Is the fitting that enters the intake manifold to which the AOS line is attached a potential problem? It has a sensor in it, can that make a difference? The other option is that I have purchased a bad AOS with a torn diaphragm. Any ideas/suggestions would be most appreciated.

Hello and welcome to the forum! Take a look at the link below to one of our site's DIY tech articles - it may help you further troubleshoot the issue.

https://www.pelicanparts.com/techarticles/Porsche-Cayenne/69-FUEL-Fixing_Common_Vacuum_Leaks/69-FUEL-Fixing_Common_Vacuum_Leaks.htm

AOS Working Correctly?
 

Through a process of elimination I believe I have narrowed my problem to the AOS and related assembly. As stated previously, I've installed a new AOS. How often can they be faulty? A new AOS with a torn diaphragm seems a bit obscure. In addition, does the fixture that enters the intake manifold with the harness attachment play any part in the amount of vacuum? I've removed and inspected it, but it appears to be a pass through? Is there a vacuum reduction function withing the valve cover itself? I've had the valve cover off previously to replace the gasket. There were no parts left over?! I am quite out of ideas here. The car is a runner but not running correctly of course. I want to get her fixed to sell, so any ideas are appreciated.