For what it's worth, my invoice from the dealer for the water pump replacement says they charged me for a "drain and bleed of the coolant as necessary" and then they charged me for 3 gallons of coolant (SLLC). This seems to indicate they drained most of it.They likely would have charged you for a new gallon of coolant as part of the job. Check your invoice (if you still have it), you might see a line item for a gallon of SLLC.