How to read PH in an antifreeze test

Written by fahlen brown
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How to read PH in an antifreeze test
Testing the pH of your car's antifreeze helps maintain the engine. (Classic Car Engine Refurbished image by Janet Wall from

Antifreeze is specifically designed to protect a car's engine from overheating and corrosion. The antifreeze removes heat from the car engine to prevent overheating. Antifreeze also has an agent that protects the engine against corrosion. Monitoring the pH of the antifreeze makes sure that the antifreeze is still protecting the engine. A too-low pH causes acid damage, and a too-high pH corrodes engine metal. Antifreeze test strips test the pH of the antifreeze. The pH value gathered from the test strips can tell you if the antifreeze in your car needs to be replaced.

Skill level:

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Things you need

  • Rubber suction bulb
  • Antifreeze test strips

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  1. 1

    Remove the cap from the radiator. Use the rubber suction bulb to take a sample of antifreeze from the radiator.

  2. 2

    Open the container of test strips and remove one strip. Replace the cap on the container to ensure that the unused test strips stay protected from outside elements.

  3. 3

    Dip the test strip into the antifreeze for one second. Remove the strip from the antifreeze.

  4. 4

    Shake the strip briskly to remove any excess antifreeze from the strip.

  5. 5

    Wait 45 seconds. Compare the colour of the strip to the pH colour chart provided with the strip kit. The recommended pH for antifreeze is any value from 7.5 to 9. Any pH out of this range indicates that the antifreeze is no longer protecting the engine and should be replaced.

  6. 6

    Match the colour of the strip with the closest colour on the pH colour chart. The colour chart will indicate the exact pH of the antifreeze. Note the number value of the pH. Green is the colour that matches the recommended pH values of the antifreeze. If the antifreeze turns the strip orange or blue, the antifreeze needs to be replaced.

  7. 7

    Dispose of the antifreeze sample and test strip.

Tips and warnings

  • For the most accurate test results, the temperature of the antifreeze sample should be between 4.44 degrees C and 43.3 degrees C.
  • Be sure to dispose of the antifreeze in accordance with your city's regulations.
  • Do not attempt to obtain an antifreeze sample from recently driven car. Hot antifreeze produces steam that can cause serious injury when the radiator cap is removed. Wait for the engine to cool before obtaining a sample.

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