The engine's cooling system for a Nissan Maxima is a complicated system involving many different parts, some of which require a working knowledge of car mechanics to replace. However, some fixes for an overheating engine can be done by virtually anyone. Familiarity with the basics of how an engine's cooling system works will help to diagnose and troubleshoot the problem before it becomes worse or can direct you to a professional mechanic.
Open your Maxima's car hood and make sure that it's propped up properly and won't close while you're looking at the engine.
Check the engine coolant to make sure that it's at an appropriate level. Make sure that your Maxima's engine is cool so that the coolant fluid doesn't burn you or cause chemical burns by exploding out from the radiator cap. The coolant can be checked while running hot by looking at the overflow reservoir to make sure that the fluid level is between the minimum and maximum level lines. Add fluid to the overflow tank, making sure that it's a 50/50 mix with distilled water. If you don't have any radiator fluid available, adding water will help to ensure that the engine doesn't overheat until you're able to obtain radiator fluid.
Test the radiator hoses for leaks, which could cause the coolant to leak out of your Maxima while driving. Turn the Maxima on and check underneath the engine for radiator fluid draining. Also check the top of the engine for any hoses that are spurting coolant while the car is running.
Test the drive-belt tension by pushing on the belt at a point halfway between pulleys. For drive belts with a distance of 7 to 11 inches between pulleys, the belt should deflect about 1/4 inch. For belts 12 to 16 inches between pulleys, the belt should deflect between 1/4 to 1/2 of an inch. Examine the belt to make sure that all of the ribs are of the same depth and that there aren't any cracks, tears or fraying. Tighten or loosen belts by using the socket wrench to turn the adjusting bolt. Drive belts should be inspected twice a year or every 6,000 miles.
Replace the thermostat. Some Maxima models will have a thermostat that can easily be removed, tested and replaced; other models will require a coolant fluid drain prior to removing the thermostat. For Maxima engines that take a long time to heat up, the thermostat is most likely stuck open. Unbolt the thermostat from the engine using the socket wrench.
