Nissan 21200-0B000 Thermostat Assembly

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To properly test a thermostat, suspend the (closed) thermostat on a string in a container of cold water, with a thermometer and heat the water on a stove. Write down the temperature when the thermostat begins to open and when it is fully open. If it doesn't work as specified, replace it. Disconnect the battery cable and drain the coolant. Remove the engine cooling fan, air cleaner, and air intake duct. Remove the upper radiator hose, unbolt the coolant tube, and loosen the hose clamp. Remove the thermostat housing cover, remove the drivebelts, and the water pump drain plug. Detach the lower radiator hose and the coolant by-pass hose, remove the intake manifold, detach the hose from the water outlet housing, and remove the water outlet cover. Scrape off any old gasket or sealant, clean them with lacquer thinner, and apply a bead of RTV sealant. Installation is the reverse of removal. Bolt the cover in place and wait for the sealant to cure. Refill and bleed the cooling system, run the engine, and check for leaks and proper operation.

First of all, before you replace the thermostat, inspect the coolant level, and temperature gauge. Detach the battery, drain coolant in your cooling system, and take off the old thermostat and install a new one. apply some sealant, let it cure, then refill and bleed the cooling system on your vehicle.

After installing the new thermostat, you should tighten the thermostat cover fasteners, reinstall the hoses, and wait for at least 30 minutes for the sealant to cure. Finally, refill and bleed the cooling system, and run the engine to check for leaks and proper operation.