Inspection

• Look at the line on the coolant reservoir bottle to see if it's full. Add 50 percent each of water and antifreeze if the level is low. Flush out antifreeze that has no color, appears rusty or has debris floating in it. Oily or sludgy-looking antifreeze may mean you have a leaking head gasket.
  
  

Testing

• Test strips---available at auto parts stores---are chemically treated to read the proper concentrations in your antifreeze. Dip the padded---or reactive---end of a test strip into your antifreeze and watch the color change to tell you whether the ph, alkalinity, buffering agent and freeze point levels are where they should be.
  
  

Temperature

• Test your antifreeze when its temperature is between 40 and 110 degrees Fahrenheit. A test strip reading will happen quicker if the antifreeze temperature is between 70 and 90 degrees Fahrenheit and the color may appear one notch darker than if the antifreeze were cooler.
  
  

Warnings

• A radiator contains a lot of pressure. The cap should be removed slowly and never when the engine is hot. Wait until the antifreeze is below 120 degrees Fahrenheit.