Q: How do you replace the thermostat in an engine cooling system on Nissan Armada?A: Drain the engine cooling system. Remove the engine cover. Remove the air intake duct between the throttle body and the air filter housing. Remove the thermostat housing cover mounting bolts, then separate the cover from the housing. Note: Leave the radiator hose attached to the housing cover unless the hose is going to be replaced. Note the position of the thermostat, then pull the thermostat out of the housing. Clean off any part of the seal that may have stuck to the housing or cover. Installation is the reverse of removal. Use a new seal during installation. Position the thermostat with the jiggle valve up, matching the index on the thermostat housing. Tighten the thermostat housing cover fasteners to the torque. Refill and bleed the cooling system. Run the engine and check for leaks and for proper thermostat operation.