2002 Mercury cougar v6 draining coolant

Thanks for your reply. Getting a few gallons of distilled water and flushing the system as you suggested is a good idea however I won't get a 50/50 mix because it's a 10 quart system and only 3 quarts drain from the radiator. Probably would have to take the thermastat out and pump some H2O out of the block. Probably easier to just have the garage do it. It's a bear to work on this car.