The Nissan 240SX uses a thermostat that is located at the end of the top radiator hose to regulate the temperature of the engine. Once the engine starts to get hot, the thermostat will open up and allow coolant to flow through the engine and cool it off. Once the engine temperature has dropped, the thermostat will close. Replacing the thermostat will help to ensure the car runs at sufficient operating temperatures.
Open the hood for access to the thermostat. Trace the upper radiator hose to the engine. The hose is connected to the radiator. The radiator is located behind the hood latch in the front of the engine compartment.
Unbolt the housing with a socket wrench and pull the housing off the engine by hand. The housing is an enclosed casing with an inlet pipe attached for the radiator hose.
Scrape the old gasket material off the bottom of the housing cover and the top of the housing casing itself with a putty knife or razor scraper. Ensure all the black material is scraped off. Failure to scrape the gasket material off will result in leaks as the new gasket will not seal adequately.
Pull the thermostat out of the housing by hand and make sure you remember which position the thermostat was sitting in the housing.
Position the new thermostat in the housing and make sure it is positioned the same as the old one. The spring side needs to be inserted first. The housing will hold the thermostat in place. There are no clips or screws involved.
Place a new gasket over the surface area of the thermostat housing. You should make sure the bolt holes match up to the bolt holes on the housing. The new gasket is included with the thermostat at purchase.
Place the cover back over the housing and tighten the cover to the housing with a socket wrench. Do not over tighten the bolts securing the cover in place.
Open the radiator cap and look at the coolant level in the radiator. The coolant level may have dropped when removing the thermostat. You should fill with coolant until the level is visible from the neck of the radiator.
Start the car and allow it to idle. Leave the radiator cap off the radiator. Allowing the car to run will push any air pockets out of the radiator neck. Fill until the level is visible at the neck. Tighten the radiator cap once the level is full.
