Radiators work by moving coolant through the engine, to prevent it from overheating. A leaking radiator can cause the system coolant to drop low enough to allow the engine to overheat and be damaged. Some leaks are easy to find because you can see the coolant dripping from a hole, scratch, or crack in the radiator or a connected hose.
Start the engine, allowing it to warm up, and watch for leaks from the radiator or connected hoses. The method of sealing the leak depends largely on the type of leak that may be present and its location. Flushing the radiator and hoses with water should make this step easier, as debris from the road could obscure holes and scratches.
Remove the metal ring around the leaking hose, and clean the radiator opening. Remove the other end and attach a new hose to both ends, also tightening the metal rings. A kinked or broken hose connected to the radiator is the simplest leak to fix.
Turn off the car, allowing the engine to cool and drain the radiator. Clean the area of the leak and patch its surface with an epoxy resin, called a “cold weld” because it will weld the hole in the radiator while the car is cold, even if it is not a traditional solder. A commercial resin should take about two hours to set and be ready for use. Although this fix can be done by someone other than a professional, the vehicle should be taken to a mechanic as soon as possible, as the fix is temporary.
Let the engine and radiator cool, and remove the radiator cap. Pour in a can or bottle of cooling system sealant, and fill the radiator with additional water or coolant. Drive the vehicle for at least half an hour, to allow the sealant to circulate through the radiator and fill the leak. Although this is also a temporary fix, refrigerant system sealants are quite effective for small leaks.
Warnings
While cooling system sealants can work very well, you should consult a professional anyway, as the sealant can cause radiator damage from deposits formed after using too much or for too long without cleaning the cooling system. . Even doing this may not prevent deposits and clogs from forming on the radiator.
