Tech Tip Corner
Coolant Contamination
Coolant Contamination
We all know that neglected coolant can lead to a clogged cooling system and a loss of cooling
system efficiency, but it can also cause other less obvious problems.
The buildup of coolant scale and deposits can coat or corrode the exposed surfaces of engine
temperature sensors, affecting their accuracy. Inaccurate sensors may send incorrect
information to the computer, and temperature controlled vacuum or electrical switches may
fail to function properly. Any of these may cause driveabiltiy problems.
If the coolantÕs age or condition canÕt be easily determined, there is a quick check for coolant
contamination using a Digital Volt-Ohm Meter (DVOM). Attach the positive DVOM lead
to the radiator, then dip the negative lead into the coolant at the filler neck.
A voltage reading of 0.2 volts or less is very good. A reading of 0.5 volts should be
considered borderline and anything over 0.7 volts is unacceptable. If the coolant fails this
test, the cooling system should be thoroughly flushed and cleaned. Remove any engine
temperature sensors and inspect them for contamination or other damage. Repair as
necessary.
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