A Science Experiment Under Your Hood

| May 03, 2005

For the six-month check, purchase a bottle of coolant test strips, either the two-way Penray Fill For Life brand or three-way Detroit Diesel Power Trac brand. Carefully review the directions on the label, especially test conditions.

First collect a small amount of coolant in a clean container. It’s safest to allow the engine to cool first so you won’t run the risk of burning yourself. Draining some coolant from the cock in the bottom of the radiator into a bottle is probably the easiest way to collect your sample.

If the coolant is very hot or cold, allow it to come close to room temperature. Test conditions require coolant between 50 degrees and 130 degrees F, so the strips will give accurate readings.

How to read the Detroit Diesel Power Trac 3-way strips:

  1. Dip the strip so all three pads are covered for one full second. Then pull the strip out and lightly flick excess coolant off into a catch pan. Note the position of the second hand on your watch.

  2. Wait 15 seconds for the top pad’s color to stabilize. Then hold the top pad next to the row of color samples that show antifreeze percentage. Note the percent glycol number next to the pad that has the color closest to the color of the strip pad.
  3. After 45 seconds, compare the color of the second or middle pad to the single colored sample on the bottle indicating the overall additive concentration.
    <li.After 60-75 seconds, compare the color of the third or bottom pad to the row of color samples indicating nitrite concentration. Note the number in ppm. The ideal figure is 1,200 ppm.

How to read the Penray 2-way strips:

  1. Dip the strip so both pads are covered for two full seconds. Then pull the strip out and lightly flick excess coolant off into a catch pan. Note the position of the second hand on your watch.

  2. After 45 seconds, compare the freeze point or upper pad to the row of freeze point sample colors on the upper row on the side of the bottle, and note the percentage.
  3. Right away, compare the color of the lower pad on the strip to the row of sample colors for nitrite concentration. Note the nitrite concentration in ppm. The ideal number is 1,200 ppm.

For both types of test strips, using a refractometer is the most precise way to read antifreeze concentration. If you have one, you may want to use it to get a more precise reading, especially if the color of the appropriate pad on the strip is right between two of the sample colors.

To use the refractometer, open up the hinged plastic cover over the light window, and then use the eyedropper supplied to get a few drops of coolant from your collection pan. Squeeze a few drops of the coolant onto the window, and then close the cover. Hold the window end of the unit toward a source of light and peer into the eyepiece. A dark line will run right across the scale and allow you to read the antifreeze concentration.

Keeping a balance
Once you know what the antifreeze concentration is, you should adjust it if necessary. The ideal concentration is 50/50 unless you live in an area where the level of protection a 50/50 mix provides, which is -34 degrees F, is not adequate. If necessary, you can use up to 60 percent concentration, which protects down to -65 degrees.

Don’t go outside this range. Using more than 60 percent will prevent the cooling system from carrying heat away from the engine’s metal parts the way it should. Using less will compromise freezing and boiling protection (allowing your cooling system to boil over too easily), and corrosion protection.

To increase the concentration, you’ll need to add straight antifreeze. To decrease it, you’ll have to add de-ionized water. You could actually use tap water from your area, provided you’ve had it tested by your antifreeze supplier and approved for use in your cooling system. Otherwise, buy de-ionized water and use that only. This is necessary because water with minerals in it will cause the SCAs to form a grit that can ruin water pump seals. They may also fail to dissolve properly and protect the system.

Once you know what the concentration is, unless it’s close to 50/50 or your desired level of freeze protection, refer to a chart like the one provided by Penray. The chart will show antifreeze concentration by percentages across the top. Each line, labeled on the left, represents a different cooling system capacity in gallons, from five to 20.

Comments are closed.

OverdriveOnline.com strives to maintain an open forum for reader opinions. Click here to read our comment policy.