Originally Posted by cv8
Despite agreeing with the dealer in advance that they would replace the check valves, they didn't. Instead they insist that the noise is coming from one of the pre-cats. I very much doubt this is the cause, but I'm willing to jump through this hoop.
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.