Hello Guys (and gals)

Okay I have a problem, I have been reading through this forum but I wanted to state my problem because I'm not sure its the same as the others.

My wife has a scion xD 2008, and just recently I noticed the engine was really loud (I rarely drive it) and then last week we switched cars and I hear this almost grinding noise in the engine.

If I'm looking in the engine, its on the left side near the alternator/belt ...it doesn't seem to effect gear change, acceleration, but I definitely hear it when I'm idling.

From what I read people are saying it could be the water pump, if so do you guys know what it takes to get that fixed, and how long I can drive on it before it blows completely.

Or if you have any other ideas why its grinding, also the grinding isn't constant, by that I mean, I always hear it grinding but sometimes its louder, sometimes it's softer, and really no particular order that I can think of. Any help would be great!