I had a crunchy bottom bracket bearing set the other day - took it out thinking its time to replace, tested it, flawless. Looked inside the bottom bracket shell, and its full of road grit from riding on wet roads, then I see theres a freeken drain hole in there that gives the water tail access from the front tire. Cleaned the bb shell out, cleaned the bb cups as they had collected some of the grit (likely making the noise), gave the threads a bit of grease, and refitted everything - runs like a dream now.
I'll construct a 1 way insulation tape vent for it, so that water can still drain, but theres no way for water off the front tire to get in...