Hi,
Pump is cooked (or close to it)
It's probably touching the engine matting surface (not good at all)
If you don't understand: The pump is bolted on the case, the case matting
surface is somewhat part of the pump assembly, when the pump bearing wear
out, it doesn't spin right anymore (not perfectly align), so the "impeller"
(sorry for my english here) is grinding the case.

Am not saying that you have reach that phase but you better change this one
before it reach the case!!!

I have seen noisy pump and they didn't damage the case, so just be aware
that if you wait to long you could end up with a bigger problem.

I have the complete step by step job on my site, check it out at:
http://www.benplace.com/water_pump.htm

Cheers, Ben
http://www.benplace.com/