the consumption may be from him not bleeding the air out all the way. as the air is working its way through the system, the top level in the radiator will lower cuz the air moves to the top. also, when you say it comsumes coolant, do you mean that radiator is low or the overflow tank is low? also could be a slow leak somewhere. the thermostat may be sticking or your car just boiled over when you went up hill. i would do the thermostat just to be safe. speculation only.