Originally Posted by David N.

2000 Boxster S, 47k miles.

I'm hearing a sound from the engine, it's like a playing card in your bike spokes. It's coming from right there at the passenger side vent, this steady ticking sound. I can hear it when it idles, and I think it's rev-related in speed. I know the belt is possibly a culprit, but I was also wondering if it could be bearings in the engine cooling fan since it sounds like it's right there at the vent.