Radiator Fluid (Antifreeze): Keeping it Cool

Radiator fluid is another one of the essential fluids in a car that is vital to proper operation. In past articles, I have talked about oil, transmission fluid, and windshield wiper fluid. So let’s continue this series on fluids with the good old green stuff, or orange, or red, or blue, or…

Which Color

Radiator fluid (antifreeze) can come in yellow, orange, red, blue, and the old familiar bright florescent green. Does it matter? Absolutely! All antifreeze is not the same.  You cannot mix different kinds of antifreeze without major issues (like damaging your entire cooling system, engine, heater core, etc.). So, what is the difference?

The difference is the chemicals used to prevent the engine cooling parts from rusting out. Corrosion is the enemy of the engine or nearly any metal for that matter.  But some systems are made of aluminum, while others are made of brass and copper. So, different chemical formulas were created.

To determine which antifreeze is the correct one for your car, check the owner’s manual. It really is the best way to be sure you use the right fluid.  Also, antifreeze comes as a concentrate or premixed. You must add distilled water (follow the label on the container) to concentrated antifreeze. However, if it is premixed (usually 50/50), you do not have to add any water. It will say clearly on the container if you need to add water or not. Once you know which fluid to use, how do you “top off” your antifreeze?

Topping Off Antifreeze

Before I go any further, a word of caution. Antifreeze is poisonous. Pets will drink it since it has a slightly sweet taste. If they do, they will die. I’m being dramatic here to drive home the point. If you spill radiator fluid, be sure to clean it up.

To check the fluid level, you need to look in two different places. First, when the engine is cool, and the top radiator hose is cool to the touch, carefully open the radiator cap. Be very careful! If the engine is hot, the radiator fluid will be under pressure and could cause severe injuries. Always make sure the engine and radiator are cool before opening the radiator cap.  After removing the cap, you should see antifreeze filled to near the top of the cap.  If not, you can add a little antifreeze to top it off.

The Reservoir

Next, check the radiator overflow reservoir. This is a container with a tube in it going from just beneath the radiator cap to the container itself.  When the antifreeze gets too hot, a valve opens and allows the fluid to enter the reservoir. When there is not enough fluid, the fluid in the reservoir is siphoned back into the cooling system.

Check to see if the level in the reservoir is between the “Add” and “Fill” markers when the car engine is cool.  If not, add the proper antifreeze until the fluid is at the proper height. More information will be in the owner’s manual.

Final Words

That’s all there is to top off the fluid. Be sure to check these levels from time-to-time. You’ll be happy you did since it could save your engine.



Written by Gary Pradel