Question: how to know if your radiator is leaking?
Answer: Drop in Coolant Level. Coolant levels gradually drop as the vehicle operates, however, a drastic drop is a telltale sign of leakage.
Puddle Underneath the Engine. When your car is parked, look out for fluid under the engine. ... 
Discoloration or Corrosion. ... 
Faulty Radiator Hoses. ... 
Frequent Engine Overheating.