Nissan 21200-0C811 Thermostat Assembly

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Before assuming the thermostat is responsible for a cooling system problem, check the coolant level, drivebelt tension and temperature gauge (or light) operation. If the engine takes a long time to warm up, the thermostat is probably stuck open and must be replaced. If the engine runs hot or overheats, a thorough test of the thermostat should be performed. To properly test a thermostat, suspend the (closed) thermostat on a length of string or wire in a container of cold water, with a thermometer (cooking type that reads beyond 212-degrees F [100-degrees C]) and heat the water on a stove while observing the temperature and the thermostat. Note the temperature when the thermostat begins to open and when it is fully open. Compare the temperatures to the Specifications. If the thermostat doesn't open and close as specified, or sticks in any position, replace it. Disconnect the cable from the negative terminal of the battery, remove the lower engine cover (if equipped), drain the coolant from the radiator and the engine block, remove the engine cooling fan, air cleaner and the air intake duct from the engine compartment, remove the upper radiator hose from the coolant outlet at the intake manifold and the radiator, remove the air conditioning compressor drivebelt and the upper idler pulley bracket, unbolt the coolant tube from the front of the engine, then 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 block, detach the lower radiator hose and the 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, scrape off any old gasket or sealant on the thermostat housing and the thermostat cover, then clean them with lacquer thinner, apply a bead of RTV sealant around the perimeter of the cover, install the new thermostat with the jiggle valve UP and bolt the cover in place within 5 minutes of applying the sealant, wait at least a half-hour for the sealant to cure, refill and bleed the cooling system, run the engine and check for leaks and proper operation.