Nissan's use of plastic radiators has grown over the last 20 years, displacing older, heavier ones made out of brass. The plastic versions are lighter, easier to repair, built to withstand heat and reinforced with glass fibers to increase their durability under pressure and high temperatures. Road debris, salt and other chemicals, however, can cause blockages, holes and cracks in the bimetal radiator. If the necessary repairs are not made, other problems can arise, affecting the vehicle's engine and radiator.
Start the vehicle so the coolant will flow from the radiator and through the engine and the rest of the cooling system. Look around under the hood for leaks in the radiator and attached hoses, as well as on the ground for green fluid. If the source of the leak is not easy to see, turn off the engine and clean the radiator's surface with a water hose or high pressured air to remove road debris that may be obscuring leaks. The actual method of repair will be determined by the type and location of the leak.
Disconnect the damaged radiator hose. Unhook the metal rings at each end of the hose. Pull the hose away from the connectors. Clean the connector openings. Place the new hose on the openings, securing it with the metal rings.
Take the radiator cap off the radiator when the engine and radiator accessories have cooled. Pour a bottle or can of radiator cooling system sealant into the radiator. Fill the rest of the room in the radiator with coolant or water. Coolant system sealant comes in powder and pellet form. Both versions work the same way --- flowing through the coolant and swelling to fill leaks. Start the vehicle and drive for at least a half hour to allow the sealant to move through the radiator and cooling system.
Stop the engine and allow it to cool. Drain the coolant from the radiator. Place the air-free plastic welder over the leak area, until it is heated all the way through. Place the air-free welder over the plastic welding rod to melt it into the leak until it begins to take on the color of the radiator. Allow the weld job to cool.