Your car overheats and loses water it is not thermostat what could it be?

need find out where you are losing antifreeze = look for leaks at radiator hoses etc first, then intake manifold top side of engine along sides of engine as well. Be careful if engine is hot .then lastly check you engine oil in case there is an internal antifreeze leak due to faulty intake manifold or head gasket. if not found have a pressure test done on the cooling system