2005 S60 2.5T, 220k

There is an intermittent loud "clacking" sound that seems to be coming from my power steering pump. There are no leaks, the reservoir is at the proper level, and I don't seem foaming or odd coloration. The pulley feels solid, no wobble. The power steering assist works fine.

Is this a sign that the power steering pump is about to go kaput? If so, I can make a run to the junkyard and swap it out.

Or is there some mystery piece inside the reservoir that could be limiting circulation? I've seen some posts about something like this, but not sure what to look for.

 

UPDATE

So upon closer inspection, noticed that the ENTIRE belt tensioner pulley was gone. The belt was riding on an empty shaft!!!
Never seen anything like it. There was just enough tension to run the PS, alternator, AC somehow. Not sure how the pulley disappeared, but the belt stayed on. Maybe since the pulley is plastic, it just disintegrated.

Either way, went to the junkyard, pulled off a belt tensioner, put on a new belt, and away we go.