Can you hear the water pump blades hit the engine block before failure?
 

I have a slight clicking sound coming from the front of my engine and to me it sounds like plastic blades scraping metal. Now I'm kinda biased as my water pump is 40k miles old and slightly leaks (but it's been doing that for a while).

What do you guys think - ever hear that noise before?

https://youtu.be/uGNNjZ-nj5s

Can't always hear a WP before it fails but if you suspect the WP blades are hitting the block, inspect it right away.

In about 20 minutes, you can remove the carpet and firewall behind the seats.

With firewall cover off, start your car and observe the WP for and signs of weeping or leaking.
Remove your serpentine belt and tug on the WP. Look for signs of wobbling or roughness when you spin the WP. You should easily be able to determine if your WP has an issue or appears normal.

I'd pull the pump and look. You don't want those plastic pieces breaking off

Since you already have the front engine cover removed; use a long handle socket to release the tension on the belt and remove it.

Then check for play in the water pump bearing. If the bearing is worn to the extent that the impeller blades can be heard hitting the block, there should be ample play in the bearing.

If no bearing play, then you'll have to investigate elsewhere to find the source of the noise.

Mine was doing that last month. Diagnosed it by removing the Serp belt and starting the car, you can run the car, if it's cold for a few minutes- 2-3 w/o flow. If the sound goes away, then it's an accessory. Then put the Serp back on and get a long blade screw driver, Don't let the Serp grab it and jam it through your face, but CAREFULLY prob around with the blade on the suspected accessory, and your ear on the end of the handle. You'll know when you here it. Mine was bad and it kind if sounded like a non localized rattle. I could see the shaft having a slight wobble when running. After i pulled it, it felt fine, but you could see where the impeller was hitting the block.

It's my alternator. And maybe the tensioner bearing too - it seems a little rough. Alternator makes noise when spinning by hand. If I spin it by the shaft (using a spline tool) and it makes noise then it's likely the internal bearing and not the pulley? Am I correct? It makes noise when spinning by the pulley as well.