Originally Posted by elp_jc
In a way that's good; if that doesn't solve the problem (as expected), pre-cats can be eliminated as a possible cause.
As far as a VANOS check-valve being the culprit, it's a heck of a lot better news than a bearing problem, so that's welcome
. Without being present to determine where the noise is coming from, we all are just making uneducated guesses. I'd like to see a detailed picture of our VANOS system, which unlike the one on S85s, does not require a high-pressure oil pump for operation. I also can't visualize what exactly can be 'clicking' (2 metal surfaces hitting each other); detailed pictures of the system would help for sure. Anyway, good luck man, and please keep us posted. And yes, it's a smart move to investigate an engine noise that wasn't there before, especially when it can be duplicated, and on cars with possible 'bad' bearings (like mine). Take care.
Check Valve Definition for VANOS:
"The check valve maintains an oil supply in the VANOS transmission and oil circuits after the engine is turned off. This prevents the possibility of piston movement (noise) within the VANOS transmission system on the next engine start."