is the recovery tank full? are the smaller return/overflow hoses in good shape properly connected?
If so you shouldn't need to burp..if properly filled.
if the above is true then you most likely have a small leak.. may not be noticeable as pressure leak, but when the coolant heatsexpands/ then starts to cool it sucks in air from somewhere.. if the pump was just replaced I'd put money on the seal around it being done improperly
Elevate the front end so that the rad fill cap is the highest point on the cooling system (six inches or so should do). Remove the fill-cap...be sure rad is full. Idle engine for 10 or 15 mins. May need to repeat.