Quick test
1 of 1
Reading the multimeter
A reading of .4 volts or less means
the coolant is good. Replace the
coolant if the reading is higher than
.4 volts.
If you think the only job of
antifreeze (coolant) is to cool
the engine during the summer and
prevent freeze-up during the winter,
read on. Coolant also plays an
important role in preventing corrosion
caused by electrolysis. Electrolysis
occurs when two dissimilar metals
start swapping electrons, causing
the metals to corrode. Since an
engine has aluminum, copper, cast
iron, steel and magnesium alloys,
electrolysis will slowly eat away at its
innards.
Coolant has additives to prevent
all of that electron swapping. But, as
coolant ages, the additives are depleted
and can't do the job anymore. In
fact, worn coolant becomes a pretty
darn good electrical conductor,
accelerating internal electrolysis. The
good news is that it's pretty easy to
check the conductivity of your
coolant with a digital multimeter. If
the conductivity is high, it's time for
a coolant flush and fill. Here's a quick
way to check it.
Begin with a cold engine. Remove
the radiator cap and start the engine.
Set your digital multimeter to DC
volts at 20 volts or less. When the
engine reaches operating temperature,
insert the positive probe directly
into the coolant. Rev the engine to
2,000 rpm and place the negative
probe on the negative battery terminal.
If the digital meter reads .4 volts
or less, your coolant is in good condition.
If it's greater than .4 volts, the electrolysis additives are exhausted,
and you may be in the market for a
new radiator, a water pump or a heater
core in the future. All of those are far
more expensive than a simple coolant
change.
Caution!
When you work on or
around a running engine,
wear safety glasses and
tight-fitting or short sleeves
to keep from being drawn
into the moving parts.
