I researched this on this Forum but did not see anything definitive so wanted to share what was found in my 2003 Bonneville

The car started having a slightly louder mechanical sound from the engine bay but it was very gradual. It sounded like the belt or one of the accessories but was hard to tell because it was only apparent in the garage or while sitting still. The noise of driving masked the sound once up to speed.

The noise became gradually louder and was definitely there when sitting at stop lights etc.

Last week I noticed a few drops of liquid on the garage floor and inspecting the water pump and pulleys, it was traced to the water pump. Also the look, smell, taste, feel all were typical antifreeze. (not Dex....I changed to Peak Extended Life (non silicate) some time ago).

Replacing the pump is not hard. No hoses have to be removed....the pump on these cars is just the front cover which contains the impeller. The old impeller bearing was shot and the impeller was loud and loose (62k miles)
The car is silent now and all is good.

Cheers,
Willydo

Good to hear. Great job tracking it down and providing help for anyone else that may have this problem. A big thanks to you.