Today, I've changed engine oil and filter to fill the gap of 10K free shceduled maintenance. After completing the work, I washed the engine bay with Simple Green to clean the dripping mess of oil. while I was cleaning the front side of engine bay, I noticed the serpentine belt tensioner was jerking, vibrating perodically. Is this a sign of failing belt tensioner? I also can hear faint metallic clicking nosie as the thensioner irradically moves.

Is this a common problem in B7 A4? Anyone replaced the one yet? BTW, the car has only ~25K miles.