After " A month " went to check the fluids! All of your coolant could have leaked out in 1 month very easy from 1 broken hose clamp. In 35 + years of trucking, Clamps fail, let you have a cold water leak, that will drip, when your unit sits for a week or so, and not leak one bit when warmed up! Do what the others say and rent , borrow, the pressure tester, from the local parts house. Check it with the city water, cold, to see if you have the cold water leak that I suspect! My bet it is a clamp that is bottomed out, and will not tighten any more, and leaking when it is cold!! My 2 cents,, No Charge!!