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Notes From the Road

The Importance of Coolant
By Debbie Murphy/

Like any other engine fluid, the coolant needs to be checked on a regular basis. You're checking for two things: quantity and condition. Since the 1970s, most vehicles have a coolant recovery tank or overflow reservoir, which makes checking the fluid level a lot easier and safer. The configuration of the radiator and tank/reservoir lets hot coolant expand into the tank as the engine temperature rises. When the engine cools down, a slight vacuum forms in the radiator and the fluid is drawn out of the tank/reservoir and back into the radiator. As long as the radiator cap remains sealed, the coolant can expand and contract without losing a drop.
You can check your coolant level simply by looking at this overflow tank. There are two level indicators on the side of the tank: one indicates the safe level when the engine is hot, the other when cold. If your coolant level is slightly low, it's safe to add a few ounces of plain water to bring the level back up to the appropriate mark. If you have to add more than a quart of liquid to the cooling system, use a glycol/water antifreeze mixture.
Nothing is ever all that simple, though. Some vehicles' recovery tanks are pressurized when the engine is hot, making the caps as dangerous to remove as radiator caps. Pressurized recovery tanks are clearly marked with warning decals and their caps is a system pressure cap, rather than a simple plug or twist-off cap.
Adding Antifreeze
If the recovery tank is completely empty, you'll need to add a mixture of antifreeze/water to the radiator. Make sure your vehicle has had at least 30 minutes, and preferably longer, to cool off, so that the radiator hose is not hot to the touch. Remove the radiator cap, checking to make sure the cap's rubber seal is in good shape, and add the mixture to the top of the radiator neck. Put the radiator cap back on securely, and add the coolant to the cold level in the recovery tank.
In addition to checking for an adequate amount of fluid, you should 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. The most common service interval for flushing the system is every two to three years, or 24,000 to 36,000 miles. When your vehicle goes longer than that timeframe without fresh fluid, you're engine may suffer some damage. So take care of your coolant—and your engine will keep its cool.

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