The thermostat in your Civic acts as a heat-sensitive valve for the cooling system. When the temperature of the coolant flowing through the engine reaches a specific degree, the thermostat opens. This process cycles out the hot coolant and allows colder coolant from the radiator to flow back in, to cool the engine. A defective thermostat may not open at all. The engine will begin to overheat and possibly rupture components like the heater core. You can locate and replace the thermostat on your 2002 Honda Civic right at home. If it has failed, fixing it should take less than 40 minutes to do.
Lift the hood on your Civic and stand directly in front of the radiator facing the windshield. Look down into the engine compartment at the back of the radiator.
Locate the bottom-lower radiator hose. It connects to the bottom, right corner of the radiator and is held in place by a metal clamp.
Follow the hose with a flashlight away from the radiator. The hose should curve to the left, then veer up vertically 14 to 16 inches and stop at the lower front of the engine. At this point, you should again see another metal clamp around the hose. The component that the hose connects to here is called the thermostat housing. Your Civic's thermostat sits right under the housing.
