A Honda Civic’s cooling system is a sealed system, meaning that it uses pressure to raise the boiling point of the fluid within the radiator. As the engine operates, the fluid within the radiator circulates throughout the engine. Most overheating problems with these vehicles can be traced to gasket failure, leaks or to worn components.
Twist the radiator cap off of the radiator after first waiting for the engine to cool, then look into the radiator and observe the fluid level. The fluid level should be approximately 1 inch below the top of the radiator. Add radiator fluid if necessary.