Originally Posted by Goran (Post 86754)

I think you're onto something there! perhaps the rubber diaphragm has failed and is vibrating as it lets air out?

Its the black plastic UFO type object at the back of the engine.

Here it is in a picture I borrowed from another forum member's post as it shows the engine bay without covers.

It is easy to remove by jubilee clip or the Audi type clip, but I'm not sure if its safe to run the engine without it or with the rubber hose plugged to test if the noise stops?
Probably ok for a minute or two, as its just a sprung rubber diaphragm to let some crankcase pressure out when it builds up enough to be able to open the diaphragm.

This is how it looks inside:

http://forums.quattroworld.com/a8/threads/8649.phtml

http://forum.a8parts.co.uk/attachmen...1&d=1420113692

Originally Posted by ainarssems (Post 86708)

Hard to say from video but it could be secondary air injection pump if the noise come from air filter box area in which case you could just temporarily disconnect it. If you have VCDS you might be able to test it using output tests or as Audi call them final control diagnosis.

Originally Posted by mark_le_b (Post 86781)

Any idea how to disconnect? Plug seems to be behind air box and I can't get my hand in there! Does air box have to come out first?

Originally Posted by Goran (Post 86885)

Are you sure you cant reach in behind the airbox and unplug it? I removed my airbox before, I am sure I unplugged it first before taking the airbox out. I just went out to the car, my SAI has been removed but I can easily reach to where the plug used to be.

Originally Posted by ainarssems (Post 86907)

There should be a fuse somewhere, not sure where. There is relay for it in electronics box in plenum chamber, fuse might be next to relay.