Hey!! I was the poster for the AOS! I literally just did mine just recently, so let me get a video up. You dont need to remove the hose to check the valve. My issue was very similar to yours.... when i first tried to take off the cap, I swear it was going to snap off and it finally loosened up. Once you have the capunscrew, have someone turn on the engine for ya and just hover the cap over the hole... you shouldn't be getting any suction at all.. maybe a slight slight resistance, but nothing too significant. Anything more than that, Id definitely look for cracks in the orange valve... I found a video on HOW to open up the AOS valve, however, DO NOT purchase that valve from that site.... it doent fit, unless you actually have a Cayanne.

 

i just did an oil change and my mechanic said he doesnt think its any issue with the AOS because he saw no leaks anywhere. before you got your AOS changed what was your oil consumption?

 

Keep in mind with the oil cap, as you're taking it off, if you turn it too far, it actually won't come off at all - at least on my car. As you rotate the cap, there are some tabs on it, not unlike a pill bottle and if you go just slightly too far counter clockwise then it won't pop off. I have to go all the way, and then back clockwise slightly to find the right position. I have no idea if this is normal or not, but the first time I tried to get the cap off to add a little oil, I spend 20 minutes trying to figure out why it wouldn't come off!!!!

 

Did you get this resolved? I am having exact same issue. Thank you!