Fan/Clicking Noise Behind Driver?
 

There is a faint noise coming from behind the driver's seat on my '99 Boxster. If I put the window down I can't hear it, only when the top/windows are up. It's difficult to describe, similar to a fan blade that isn't balanced properly.

I don't believe the left intake has a fan, could it be the timing belt? What else is behind the driver that could be making a clicking noise at perfectly timed intervals?

I'm coming up on my 75k service, but I am wondering if I should be concerned and take it in sooner. Thanks!

Well, the Boxster does not use a timing belt; it uses a timing chain, so that eliminates that, but there is a drive/serpentine belt. You can try running the engine with the engine cover removed so you can hear it better, and perhaps record the sound.

Might be worth the time to remove the engine cover both on top and behind your seat and see if you noise is coming from the cam chain tensioner that sits right behind the drivers seat. It may need replacing. Just a thought...

One more thought might be as simple as an idler pulley. Mine started making a 'faint' clicking noise. The faster the engine was revved, the faster the noise.

Hit the pulley with some WD-40 (magical stuff-careful not get any on the belt) and the noise went away. This solution will ONLY BE TEMPORARY but provides time needed to order part, get it delivered and installed.

Either way, your answer lies in opening the bay up and listening more intently to where the noise is coming from….or as KennyBoxster suggested, record it and post it.

Good Luck!