I am a mechanical engineer with a new-to-me 2007 A4 2.0T with the "characteristic" knocking sound that I am convinced shouldn't be there even if it is "normal". Stethoscope inspection strongly indicates it is the oil pump cam so in preparation for removing the pump and inspecting i bought a replacement follower and noticed that there is a circlip at the top, presumably to stop it falling into the engine if anyone removes the end housing with the fuel pump still installed in it. It occurred to me that this circlip might be limiting the travel of the follower and preventing contact with the cam in the low spot, hence breaking the oil film and also causing noise on re-contact. If Audi designed that lower position of the follower to be "just" in contact with the cam, then manufacturing tolerances might explain the variability of this phenomenon. Has anyone tried simply removing this circlip? Does this make sense? I haven't disassembled and measured everything yet. Might then run like a sewing machine, not to mention the follower lasting much longer because of better lubrication and not being hammered. Warning label on the top of the engine regarding the missing circlip would be advisable...I have previously owned a 1.8T so know what it should sound like at its best.

 

Sorry, way to advanced for me. My car has the ticking noise, but no knocking. Would love to see what you figure out and if it makes a difference.