If you drive in snowy weather conditions, make sure you wash the radiator when you wash the rest of the car. Road salt that's put on roads to melt snow is the primary cause of external radiator corrosion.

2torial #0714: Learn2 Flush a Car Radiator (Continued) Remove the radiator pressure cap Cover the radiator cap with a rag. You've made sure the engine is cold, but go slowly anyway. Most radiators now have a fill spout that is slanted slightly towards the windshield of the vehicle to avoid mishaps, but caution is never wasted. Put on eye protection and sturdy, preferably waterproof gloves. Never lean over the radiator when removing its cap. The contents of a radiator can be under pressure even with a cold engine, and you don't want any unpleasant surprises. With the heel of your hand, press down firmly, turn the cap a quarter turn to the left. You'll feel the cap is loose when you move it, but it's still locked on. (This first turn is to release any pressure in the radiator.) Then, pressing down once more, turn the cap another quarter turn to the left and take it off.   Step 4