A friend with a CC changed his flat engine belts and noticed that a tensioner felt "gritty". When we went to check mine for comparison we found that one of my belts was in bad shape so I bought a new one and went to install it. The flat pulley on the water pump wiggled and I found that the bearings were going. Cost was $169 and a little antifreeze and a couple of hours work. That sucker would have gone out somewhere where there would have been none for sure!
We'll take lucky when it's offered! That's almost how I lucked into discovering the siezed idler pulley bearings just before they finished breaking the shaft they rode on...My preflight walkaraound gets bigger and bigger because of anecdotes like this...