coolant leak on 1994 Mercedes-Benz S500

coolant leaks from middle of motor under car and seem to overheat,already replaced thermostat,water pump seemsok could it be a freeze plug?

Asked by for the 1994 Mercedes-Benz S500
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.