Answer: Antifreeze protects your engine fluid from freezing or boiling. It is very important to check the level and condition of your antifreeze regularly. Coolant levels should be checked only when an engine is completely cool. Engine coolant may still be very hot and can lead to burns if you check your coolant levels too early. Any significant loss of antifreeze usually means you have a leak or your engine is running too hot. Driving on old engine coolant is one of the leading sources of cooling system failures. This means that your engine is too cold to start or overheats and shuts down. An engine that is overheating can soon self-destruct.