Hondas use the standard spring-located thermostat to regulate engine temperatures on its 1998 CRV. When the coolant in the engine reaches 87.8 degrees C, the spring compresses to increase the flow rate of fluid through the engine and radiator. The increased passage of fluid into the radiator lowers the operating temperature of the Honda CRV. When the thermostat fails, you must replace it with one that works properly to avoid costly engine failure.
Disconnect the negative battery cable from the battery of the CRV with an adjustable wrench.
Open the petcock located on the bottom of the radiator and drain all of the coolant from the radiator into a sealable drainage pan. Close the petcock once finished.
Follow the upper radiator hose from the CRV's radiator to the point where the hose connects to the top of the engine. The metal cover the hose connects to houses the thermostat.
Remove the two mounting bolts that hold the lid onto the thermostat housing with a 10mm socket and ratchet.
Pull upward on the lid with your hands. The thermostat housing uses a rubber seal instead of the traditional paper gasket to seal the top and bottom half of the thermostat housing.
Remove the rubber seal and the thermostat from the housing. Discard both.
Place the thermostat into the bottom half of the housing (part of the housing still connected to the engine) with the pin or "jiggle valve" resting inside the bottom half.
Wipe the mating surfaces of the bottom half of the housing and the lid of the housing off with a shop towel.
Place the rubber seal supplied with the replacement thermostat onto the mating surface of the bottom half of the housing, then place the lid on top of the seal. Secure everything into place with the two 10mm bolts.
Reconnect the negative battery cable.
Open the cap on the radiator overflow tank located beside the radiator and drain the coolant back into the engine. Run the CRV for five minutes with the cap open to expel any air trapped in the coolant system. Close the cap after five minutes.