You will need to identify the problem. Fill the coolant tank and run the car for a while and look for the source of the leak. The water pump is at the passenger side end of the engine and the thermostat is on the front of the engine block. Also look at all the water hoses. You should be able to spot the source of the leak and can replace that part. However, when doing it yourself (and depending on the age of the vehicle) you might replace water pump, thermostat, hoses and belts all at once.
I have a question if dealer replaced my coolant Outlet valve do I still have the old coolant in there or would they have put fresh coolant in? Just curious because car is coming up on 5 years old . I know you're supposed to flush it five years or 150000 miles although I only have 60,000 miles almost