a water pump that ive seen usually has a whinning sound check your belt tension then the pulley itself with the belt off and see how it moves with just you turning it.. i had to replace mine but it gave no signs no sounds or anything it was the internal impeller seal that went and was slowly...
no heat at all on lower hose? is there a sweet coolant smell in the car when your heater and vents are off? replace t-stat and come back with results it sounds like its stuck closed.. any leaks or noise by water pump?
similar situation here except when my overflow was boiling it ended up being my waterpump and not the gasket like i expected once removed i noticed that it was the impeller seal.. so during that replacement since timing belt was off i decided to install a coemetic thick head gasket and arp studs...