A hydrometer test will indicate whether ethylene glycol and/or water should be added to maintain the desired freezing point of the solution. The freezing point of the solution should give protection to an acceptable range of -37  to -47°C (-35 to -45°F) regardless of climate conditions. This is also necessary to provide adequate corrosion protection.

Some devices used for testing solutions will indicate the correct freezing point only when tested at a specific temperature. Other testers provide thermometers and tables indicating freezing points corresponding to readings made at various temperatures. Disregarding the temperature of the solution when testing may cause an error as large as 15°C (30°F) in determining freezing points.

Tools Required

All new vehicles are produced with coolant that can be accurately measured with a hydrometer. However, when the type and quality of the coolant being measured is unknown, such as in a customer vehicle that has accumulated mileage, the use of a refractometer is recommended.

Coolant testers J 26568 and J 23688 can be used to check the antifreeze protection on the coolant. Make sure the refractometer markings are correct. Unless the J 26568 or the J 23688 has a provision for temperature correction, test the coolant at the temperature for which the tester was calibrated. If the coolant is warmer or cooler, the reading may be incorrect. Follow the manufacturer's directions when using the J 26568 or the J 23688 .

1. Before each use, open the plastic cover at the slanted end of a J 26568 or a J 23688 in order to expose the measuring window and the bottom of the plastic cover.
2. Wipe the cover dry with a tissue or clean, soft cloth.
3. Close the plastic cover.
4. Do not remove the clear plastic pump from the J 26568 or J 23688 .
5. Release the tip of the pump from the tester.



6. Insert the tip of the pump into the radiator filler neck. Ensure that the tip of the pump is below the level of the coolant.
7. Press the release bulb to get a sample.
8. Insert the tip of the pump into the cover plate opening.
9. Press the bulb and allow a few drops to fall onto the measuring surface.

Important: Do not open the plastic cover when taking readings because water evaporation can change readings.




10. Point the J 26568 or J 23688 toward any light and look into the eyepiece.

•	The coolant protection reading is at the point where the dividing line between light and dark crosses the scale. Antifreeze protection is the scale on the right.

•	The temperature scale is reversed from a standard thermometer scale.

•	Below zero readings are on the upper half of the scale.

•	If the readings are not clear, the measuring surfaces were not wiped and properly dried. Wipe the surfaces dry and conduct the test again.