GM 25199828 Thermostat Assembly, Engine Coolant (W/Gasket)

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Before assuming the thermostat is to blame for a cooling system problem, it is important to check the coolant level, drivebelt tension, and temperature gauge operation. If the engine seems to be taking a long time to warm up, based on heater output or temperature gauge operation, it is likely that the thermostat is stuck open and should be replaced with a new one. On the other hand, if the engine runs hot and the radiator hose attached to the thermostat housing is not hot, it indicates that the thermostat is probably stuck closed, preventing the coolant from escaping to the radiator. In this case, the thermostat should be replaced. However, if the radiator hose is hot, it means that the coolant is flowing and the thermostat is open. To remove the thermostat, start by disconnecting the cable from the negative terminal of the battery and draining the cooling system. Then, disconnect the air filter outlet duct and remove the PCV vent pipe from the turbocharger (for 2015 and earlier 1.4L engines) or detach the throttle body coolant hose and the heater hose from the thermostat housing (for 1.8L engines). Next, remove the radiator hose retaining clip or clamp and detach the hose from the thermostat housing. After that, remove the fasteners and detach the thermostat housing, tapping it with a soft-face hammer if it is stuck. Clean the mating surfaces of the housing and cover. To install the new thermostat, insert a new gasket into the groove in the housing and reconnect the hose to the base of the thermostat housing and attach the clamp (for 2015 and earlier 1.4L engines). Then, install the thermostat housing and bolts, tightening the bolts to the specified torque. For 1.8L engines, reconnect the heater hose and the throttle body hose to the thermostat housing. Reattach the radiator hose to the outlet pipe on the thermostat cover and install the clip or clamp. Finally, refill the cooling system, reconnect the battery, start the engine, and allow it to reach normal operating temperature. Check for leaks and proper thermostat operation.