Gene, I don't get the comment, "Assume pump 30k mi, because t beld tone by reliable indy" -- was the pump done or wasn't it? A reliable indy will assess the pump when the thing is apart and make a decision -- I've replaced the pump whilst in there and I've also put it back together if the bearing is tight and the thing isn't leaking. A leak can be hard to see because of the way the cog is designed and where the fluid would go. Also, the heat from the engine tends to evaporate a lot of fluid, so the leak has to be huge to be visible. Remove or loosen the belt, remove the fan, then assess the bearing.
Yes, the cog nuts can be loose. Check it out.
Another thing that can happen is the fan itself (4 or 3 hex bolts) can get out of balance due to a bolt getting a little loose. That'll kill a water pump with some time, too.
best, whit