2005 Nissan Altima Replace a Thermostat

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The thermostat inside the 2005 Nissan Altima engine has a temperature sensitive spring on the bottom of it that opens and closes the thermostat, depending on the temperature of the engine. Once the engine reaches its operating temperature, the spring pushes the thermostat up and allows the antifreeze to flow out of the radiator and throughout the engine to keep it cool. If the thermostat gets stuck, it can cause the engine to overheat. Change the thermostat immediately once it begins to stick.

Tools Used[edit]

Drip pan
Flat head screwdriver
3/8-inch drive ratchet
3/8-inch drive socket set (Metric)
Flat metal scraper
Clean rags
Red high temperature silicone
New thermostat with gasket

Replace a Thermostat[edit]

  • Park the 2005 Nissan Altima in a safe work area and turn the engine off. Engage the parking brake and open the hood. Wait a couple of hours for the engine to completely cool down.
  • Touch the radiator cap to make sure that it has cooled down. Loosen and remove the radiator cap and set it to the side.
  • Slide a drip pan underneath the drain plug on the bottom of the radiator. Open the drain valve with pliers and allow one or two gallons of coolant to flow into the drip pan. Tighten the drain plug with the pliers. This process will lower the coolant level below the thermostat housing, and prevent coolant from spraying everywhere when you are replacing the thermostat.
  • Locate the thermostat housing by following the bottom radiator hose from the radiator to the engine block. The other end of the bottom radiator hose attaches to the thermostat housing port on the bottom side of the engine. Loosen the clamp from the radiator hose where it is secured to the thermostat housing port, using a flathead screwdriver. Pull the clamp back onto the hose. Twist the hose counterclockwise and pull it straight off the port.
  • Loosen and remove the two metric bolts that secure the thermostat housing to the engine block with a ratchet and a metric socket. Pull the thermostat housing off the engine block and place it to the side. Pull the thermostat out of the engine block and match it to the new thermostat to ensure that it is the proper size.
  • Insert the new thermostat into the engine block with the spring inside of the engine block. Scrape away any excess gasket from the base of the engine block around the thermostat and from the base of the thermostat housing. Wipe away the excess gasket with a clean rag.
  • Spread a generous amount of red high-temperature silicone around the base of the thermostat housing. Attach the gasket to the base with the holes of the gasket matched up with the holes of the housing. The silicone will hold the gasket in place. Position the thermostat housing back over the thermostat and screw the two mounting bolts back into the housing. Tighten the bolts with the ratchet and socket.
  • Slide the bottom radiator hose back onto the thermostat housing port. Position the hose clamp back over the hose and the port. Tighten the clamp with the flat head screwdriver.
  • Fill the radiator back up with antifreeze until the fluid level stabilizes at the top of the fill neck. Crank the engine and wait for the engine to reach operating temperature. This will allow the thermostat to open. Once the thermostat opens, the fluid level will drop inside of the radiator. Add more antifreeze to the radiator until the fluid level level stabilizes at the top of the fill neck with the engine running. Screw the radiator cap back onto the radiator.
  • Shut the engine off and inspect the thermostat housing for any leaks. Close the hood and pull the drip pan out from under the Altima.

Tips & Warnings[edit]

  • The red high-temperature silicone not only holds the gasket in place, but forms a secondary gasket that can withstand high temperatures. You can buy the silicone at most auto parts stores.
  • Never attempt to work on a vehicle when the engine is still hot. Removing the cap from a hot pressurized radiator can result in serious burns.