Assuming the mechanic did replace the pump. He worked on it a second time, but only so far as re-tightening the bolts. What is the most likely cause of the continued leak? Is it the O ring that connects to the engine? Is it a bad gasket connecting the two halves? Is it a tube connecting to the pump?
It is odd that it will only leak when the engine is cold, or when I apply pressure to the upper radiator hose. When the engine is cold, it will drip, drip drip when I add coolant. Loses between a quart and half gallon after each trip.