Engine 2014 Mustang V6 leaking coolant

That is the 'weep hole'. It is to let you know, your water pump is going bad. The bearing and seal is worn out causing a small leak from the 'weep hole'. I know a woman whose water pump went out. I changed it for her and I asked her if she has had to add water to the radiator, she told me she had been adding a quart every 5-6 days of antifreeze to it for over a year. It can leak from the 'weep hole' for a few days or a long time before the seal lets loose and dumps all your coolant