Having a radiator coolant leak is one of the leading causes of engine failure. Engines produce extreme amounts of heat when they operate. The cooling system pumps antifreeze coolant through the engine to draw heat away from it. That is why keeping your radiator leak free is key to having a healthy automobile.
Place a large, clean, flattened cardboard box under the front of the vehicle when it is parked for the night. Make sure the vehicle is on a level surface. The next morning, any drips from the cooling system will be visible on the cardboard. This will lead you to the approximate area of the leak. Open the hood and look around the regions corresponding to the drip areas on the cardboard. If the leak is on the radiator, there will be evidence of dried radiator coolant. A leak at a fitting or gasket will appear on the engine as dried or wet areas of antifreeze coolant. Run your finger around the hoses where they attach to the radiator and engine. Leaks at the hose clamp will result in moisture on your finger.
If the leak was found on the radiator, check to see if it has plastic side tanks. Tapping or lightly scratching either one of the side tanks will show you if the tank is plastic or metal. Open the radiator cap and pour in the radiator sealant (follow the manufacturer instructions). If a commercially sold sealant is not available, ground black pepper can be used. Add 1 or 2 tablespoons of pepper into the radiator. Pepper as a sealant works fine on small leaks. If you found that you have plastic side tanks, then this fix will only be temporary. Start looking for a replacement radiator, as the price to refurbish this type is usually not cost effective.
For hose leaks around the hose clamp, a simple tightening of the clamp usually fixes the problem. Sometimes a small tear occurs where the hose attaches to the fitting. The hose can be removed and the defective area cut away using a razor blade. The hose can then be reattached to the fitting leak free. If the leak was on the hose body, then it must be wrapped with either duct tape or wrap seal. Unless this is an emergency repair, make sure the hose is very clean before applying tape or wrap seal. Use overlapping wraps and extend the tape past the area of the leak in both directions. These are by no means permanent fixes, and a new hose should be put on as soon as possible.
Leaks can be fixed on a temporary and permanent basis depending on the type. However, most modern radiators are metal and plastic combinations, and they are typically not economical to repair. A radiator should never be replaced without new hoses, radiator cap and coolant.