Coolant, also known as antifreeze, prevents your car from overheating. If your car overheats for too long, it could blow a head gasket, allowing the water and oil to mix, ruining the engine. You should check and change your coolant every two or three years.http://news.carjunky.com/how_stuff_works/how-to-check-change-antifreeze-coolant-abc568.shtml 

1. Locate the coolant reservoir, next to the radiator with a hose running to it for overflow. The side of the reservoir will have levels marked for minimum or maximum.
2. When your engine is cool, remove the cap of the coolant reservoir. You should see the antifreeze inside, usually green or orange in color. Refer to your Owner's Manual to find out which specific type of antifreeze your car requires.
3. Use a funnel to add coolant to the reservoir. Make sure you do not overfill the coolant reservoir or the engine could flood.
4. Recap the coolant reservoir and you're ready to go!http://www.youtube.com/watch?v=CVEmn4KKLsM&feature=player_embedded#at=157 http://www.autoupkeep.com/LCChapter6.htm