Nissan Repair: problem with 97 nissan altima 2.4 engine, radiator cap, nissan altima

Question
I had a question and i was hoping you might be able to answer it. The coolant isnt traveling through the reservoir to the radiator...what may be the problem?

Answer
Hi, The coolant reservoir is nothing but an "expansion tank" When the coolant in the radiator gets hot, it expands and creates pressure. This pressure, pushes the spring of the radiator cap up, thus allowing the coolant to escape through a small rubber hose, or the radiator it would explode! But we don't want that coolant to be wasted on the ground, so we simply drive it to that expansion tank! When the radiator cools off and the coolant in it gets cold, a vacuum is created and that vacuum sucks the liquid from the expansion tank back into the radiator. Follow the directions that indicate how much coolant should be in that reservoir, when the engine is cold!!! We never fill it all the way up because the hot coolant, when the motor warms up, it will push it out of it creating a mess! If everything works as it should but the coolant does not travel back to the radiator, then we probably have a bad radiator cap or a leaky hose from the reservoir to the radiator. Have the Radiator cap checked with a special cap tester tool. I'm not sure but I believe the Autozone can do this test for free.