Mopar 4778975 THRMOSTAT

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Before assuming the thermostat is to blame for a cooling system problem, check the coolant level, drivebelt tension, and temperature gauge operation. If the engine seems to be taking a long time to warm up, the thermostat is probably stuck open. Replace the thermostat with a new one. If the engine runs hot, use your hand to check the temperature of the upper radiator hose. If the hose isn't hot, but the engine is, the thermostat is probably stuck closed. Replace the thermostat. If the upper radiator hose is hot, it means that the coolant is flowing and the thermostat is open. To replace the thermostat, disconnect the negative battery cable, drain the cooling system, and locate the thermostat housing. Loosen the hose clamp(s) and detach the hose(s) from the fitting(s). If a hose is stuck, twist it to break the seal and pull it off. If a hose is old or deteriorated, cut it off and install a new one. Remove the bolts and detach the housing cover. Note how it's installed, then remove the thermostat. Clean the gasket mating surfaces with lacquer thinner or acetone. Install the new thermostat in the housing, apply RTV sealant to both sides of the new gasket, and position it on the housing. Install the cover bolts, reattach the hose(s) and tighten the hose clamp(s) securely. Refill the cooling system, start the engine, and check for leaks and proper thermostat operation.