Like any other engine fluid, the coolant needs to be checked on a regular basis. We're checking for two things: quantity and condition.

In addition to checking for an adequate amount of fluid, we examine the condition of the fluid. Coolant that's still working looks like clear, slightly thick lemonade, a pale greenish-yellow color. Long-life coolants are orange, like pale orangeade. Some vehicle manufacturers employ a beige-colored fluid. No matter what the color, the key is that it's not brownish or dirty looking and that flecks of rust aren't floating around in it.

If the coolant is in bad condition, it's time to have the system flushed.