I have a coolant leak that appears to be coming out of a nut beneath the water pump housing. The nut is impossible to get to (of course) but it sits vertically, in a gap between the fins of the water pump housing. I haven't figured out what this nut is, what it is attached to or how on earth I'm going to get to it. It looks like a gasket or seal beneath the nut. Gravity means it drips even when the engine is off, and when on it drips more rapidly. Ironically it seems to have happened just after my radiator was repaired. Any suggestions very welcome. Cheers.