Nissan began selling pickups in the U.S. in 1958. In the 1986 model year, Nissan released a new pickup truck and called it the Hardbody. The 1995 Hardbody came standard with a 2.4-liter, four-cylinder engine that produced 134 horsepower and had an available 3.0-liter V-6 that created 153 horsepower. A mixture of antifreeze and water, along with a thermostat that opened and closed to control the flow of the water and antifreeze, regulated the temperature of these engines. Replacing the thermostat in either the V-6 or four-cylinder engine is easy, and the processes for the two engines are nearly identical.
Raise the front of the Nissan with a floor jack and slide jack stands beneath the vehicle's frame rails. Lower the truck until only the jack stands support its weight.
Slide under the Nissan truck and locate the radiator drain plug under the lower radiator hose -- the rubber hose on the bottom of the radiator. Place the drain pan under the drain plug and remove the plug with a ratchet and socket. Allow all of the coolant to drain into the drain pan.
Reinsert the drain plug and tighten it with a ratchet and socket. Raise the truck from the jack stands with the floor jack, and remove the jack stands. Lower the truck to the ground.
Open the truck's hood.
Locate the upper radiator hose and trace it until you meet the metal housing connecting the hose to the engine, this is the thermostat housing. Remove the three bolts holding the thermostat housing to the engine with a ratchet and socket, and pull the housing away from the engine. This exposes the thermostat below the housing.
Grab the thermostat and pull it from the engine. Insert the new thermostat into the engine with the spring part going into the engine and the jiggle valve -- the small valve on the perimeter of the thermostat -- facing upward.
Scrape the mating surface on the thermostat housing and engine with a plastic gasket scraper to remove the old gasket and any debris. Never scrape these surfaces with a metal scraper, as it may cause damage to the mating surface and result in a leak.
Place a new gasket on the thermostat housing, on the V-6 engine, and press the bolts through the holes in the housing to secure the gasket. Apply a bead of liquid gasket around the mating surface on the four-cylinder engine.
Set the thermostat housing in place over the thermostat and tighten the bolts from 12 to 15 foot-pounds on the V-6 engine and 5 to 6 foot-pounds on the four-cylinder engine, using a torque wrench and socket.
Allow the liquid gasket to dry for approximately 30 minutes on the four-cylinder engine.
Open the radiator cap and fill the radiator with 50-50 premixed coolant. Start the engine and allow it to warm to operating temperature. Add coolant each time the level drops, the coolant should drop three or four times as it circulates through the engine.
Close the radiator cap when the coolant level remains steady and the radiator is full. Shut the engine down.
Allow the engine to cool and check the coolant level in the coolant reservoir. Add 50-50 premixed coolant to the reservoir until it reaches the "Max" line on the reservoir, if needed. The 2.4-liter engine holds a capacity of 2.15 gallons of coolant and the 3.0-liter holds 2.85 gallons.
Close the Nissan's hood.
Take the old coolant to a used automotive fluid recycling center for proper disposal. Most auto parts stores perform this task free of charge.
