Cold start of engine (IE sitting for a day or so) when engine first fires a noise is audible for 1-3 seconds. Common sounds is a "rattling", "ringing", "clanking", or otherwise described as a horrible sound. Then the sounds is gone, warm starts, I will never hear this sound.
Audi's answer so far:
The camshaft adjustment is hydraulically actuated and controlled by the engine oil pressure. If the engine has been turned off for a long time, the oil pressure drops down and the oil partially flows back into the oil sump.
To ensure an efficient camshaft adjustment right after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as fast as possible. During this time, a rattle or knocking noise may be noticeable.
This noise is normal at engine start and will last until the oil pressure is fully built up, which takes about 1-2 seconds.
Replacing the Camshaft Tensioner(s) or Camshaft Adjuster(s) will not eliminate this noise.
My Issue with this answer:
The car never did this new, it's progressively gotten worse over time. IE a part or parts are slowly going bad and should be repaired.
So after hearing my local Audi dealerships answer I called around to various mechanics who service Audi's. They all said, this is very common especially in the 2004 Audi S4. The problem is one or both timing chain tensioners or the camshaft adjusters are going bad, symptoms all lead to this. The bleed off ball valves are clogged and the tensioners lose oil pressure over time. THIS SHOULD BE A FIXABLE PROBLEM FROM AUDI, IE CPO OR APPP and they can't see why a dealership wouldn't fix this issue, it's a 15hr paid fix!
I have read over this entire post. http://www.audizine.com/forum/showthread.php?t=246077 and some of the information is relevant, but not specific to the question. This question isn't related to 100,000 mile cars needing regular service on a warn motor, this is related to even low mileage motors with a problem that SHOULD BE FIXED under warranty.
So this seems to be extremely common with 4.2L S4's from my recent searches on various forums online. Nobody posted the year of the vehicle described. I can't narrow down this to just 2004 models yet.
What I would like from the users of AudiZine is a extremely brief description of your cars year, mileage and if you hear the same noise or not? Have you gotten this fixed or looked into? CPO warranty covered, or Audi Pure Protection Plan Platinum covered?
I have a 2004 Audi S4, 33k miles, Yes I hear the ringing sound on cold startup, then it goes away.
Your time and information is greatly appreciated.
PS. I'm going to add everyone info to an excel chart.
Thanks for all your participation on this thread. I believe the results speak for them self. If this ever becomes an issue beyond 1-2 second startup, I imagine we'll all know about it.
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I know the inside video is a little hard to hear with the clutter of the keys and whatever, but you can definitely hear it if you play it a few times.
Inside the car video
Outside the car video
I condensed everyones posts into a Excel list so you can order results ascending/descending by post, year, mileage, symptoms(yes/no) and username.
AZ_Chain_Rattle_Results.xls It's a safe file.
Here is what the file looks like, a preview.