Engine Coolant Testing

Using an antifreeze hydrometer.

The cooling system requires a 50/50 mixture of antifreeze and water. Antifreeze protects the engine’s cooling system from rust and deposits while keeping it from freezing during the winter and overheating in the summer heat. There are several ways technicians test the engines coolant.

Antifreeze hydrometers quickly indicate the freezing and boiling points of an engine’s coolant. There’s a label attached to each side of the testers see through body. One side shows the coolants boiling point and the other side shows the freezing point.

Antifreeze tester hydrometer

Look for a reading of -34° F on the freeze point side and a reading of 265° F on the boiling point side of the tester. The see through body of a hydrometer is handy for inspecting the condition of the coolant; looking for rust and contaminants.

Test strips also test the alkalinity of the engine’s coolant. As coolant wears it becomes acidic and the PH balance changes. Electrolysis, combustion gases, and hard water affect the coolants PH.

Insert the strip into the coolant for a couple of seconds, then let it dry for about a minute or so. The color of the strip will change. Just match the color on the strip to the color on the label.