Nissan 21200-42L06 Thermostat Assembly

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Before attributing cooling system issues to the thermostat, it's important to check several factors. Verify the coolant level, assess drivebelt tension, and ensure the temperature gauge (or light) is functioning properly.

To replace a thermostat, follow these steps: Disconnect the battery's negative terminal and, if applicable, remove the lower engine cover. Drain the coolant from both the radiator and the engine block. Remove the engine cooling fan, air cleaner, and air intake duct from the engine compartment. Disconnect the upper radiator hose from the coolant outlet at both the intake manifold and the radiator. Remove the air conditioning compressor drivebelt and upper idler pulley bracket. Unbolt the coolant tube from the front of the engine. Loosen the hose clamp and detach the lower radiator hose from the thermostat housing cover. Remove the thermostat housing cover from the engine. Remove the drivebelts and the water pump drain plug from the front of the engine. Detach the lower radiator hose and coolant by-pass hose from the thermostat housing cover. Remove the intake manifold from the engine. Detach the hose from the water outlet housing and remove the water outlet cover from the engine. Clean off any old gasket or sealant on the thermostat housing and thermostat cover using lacquer thinner. Apply a bead of RTV sealant around the perimeter of the thermostat cover. Install the new thermostat with the jiggle valve facing upward and bolt the cover in place within 5 minutes of applying the sealant. Wait at least half an hour for the sealant to cure. Refill and bleed the cooling system. Run the engine and check for leaks and proper operation.