coolant leak

Your coolant leak will usually fall to the center of the vehicle due to the gravel shield under the engine. I'd pressure test the cooling system and then go around the engine compartment with a flashlight and mirror until you find the source of the leak. Without knowing the miles it's a little harder to make an educated guess as to what the leak may be. Freeze plugs rarely leak. Common leaks are plastic connector pipe at firewall and water pump.