Video short showing how to replace a thermostat on a 8th generation Honda Civic equipped with the 1.8 liter 4 cylinder engine (R18A). This procedure will be very similar for later-generation hondas that use variations of the R18 motor. It is important to ensure the cooling system is completely filled after air is introduced into the cooling circuit. Having a faulty thermostat can result in an engine overheating or underheating such that the engine is not being run at optimal temperatures. This will eventually throw a P0126 check engine code. Lastly, a thermostat that is stuck open or opening prematurely can result in a vehicle with insufficient cabin heat. Cooling systems should be refilled with only genuine Honda coolant