weeping from the water pump housing

If you're talking about the bolt that I'm thinking of, it is actually the drain point for the housing. If we're talking about the same thing here, there should be a copper washer / gasket on the bolt. Perhaps your leakage stems from that. Unfortunately, if you pull the bolt, you may loose some coolant. I say some becasue as long as everything else in the cooling circuit is sealed off (radiator cap, radiator bleeder, etc...) there shuldn't be that much leakage since there is no air availabel to replace the loss in liquid volume of the cooling circuit.