The coolant reservoir sits nearby the battery, located in the extreme right front corner of the engine bay in Xterra and Frontier vehicles. Free the hose from the reservoir, unscrew the bolts holding it, and lift the reservoir straight out of its bracket. Pour the coolant into a container. Rinse and clean the reservoir completely, then check it for any cracks or wear marks; swap it for a new one if it won't read properly or shows damage. Installation is the reverse of removal. Before you start, remove the battery cable from its negative terminal. Place the transmission gear lever in park lock, engage the handbrake, block the rear tires, and safely raise your vehicle's front end using jackstands. Take out all the coolant, bottling it up when it's fresh and good to go again. If your car has automatic transmission cooler lines hooked up to the radiator, disconnect them by placing a pan under the drip to catch spills, and plug each line and fitting with a stopper. Work your way around the hose clamps with pliers to loosen them. Use slip joint pliers to take the radiator hoses off the radiator, gently breaking any sticking point. Pull off the small hose that links to the fluid holding tank attached to the radiator opening. Take out the cooling fan from the engine, remove the small brackets that fix the top of the radiator to the support, and move the radiator up with the fan shroud on top carefully, making sure not to drip or scratch it. Check if the radiator is leaking or broken, and fix it by bringing it to a repair shop when needed. First clean out all insects and mess behind the radiator using water from a garden hose. Later, drain out any remaining fluid before replacing the unit. Look for cracks in the metal supports that hold the radiator and replace them if you find any. You slide the radiator back into place until all its mount points secure firmly. Test the system by filling the cooling system, letting the engine run to spot possible leaks, and let it reach normal working temperature. When the vehicle is chilled down, check the coolant level again, top it off if necessary. Then, look at the automatic transmission fluid and top it up if it's low.