Radiators and heaters have
undergone considerable improvement. And we have had superior
antifreezes in recent years (even before the introduction of the
orange organic acid type). So it seems hard to believe that so
many radiators and heaters fail from inside-out corrosion and
perforation. Of course, vehicles are being kept in service much
longer (thank high sticker prices for that), so eventually even
better systems will fail. But in addition to low antifreeze
protection and depleted inhibitors, there are other specific
problems that contribute to the perforation failures.
The most significant is
electrolysis ó the flow of stray current that gets into the
coolant and flows through the radiator (even along the radiator
hoses) and through the radiator core to electrical ground.
Although electrolysis is a single problem, it has many possible
When a radiator fails in a
short amount of time/mileage, and you know the coolant was a
recently installed name brand, check for electrolysis. Ground
the negative lead of a digital voltmeter to the battery negative
(ground) post or side terminal, then insert the positive lead
into the coolant itself (making sure the tip doesnít touch a
metal neck or core of a radiator). If you get a reading of 0.3
volts or higher, thatís excessive electrolysis ó bad news. Older
cast-iron engines could tolerate that, but the modern engine
with all its aluminum components cannot.
One of the worst cases we saw
occurred in just 30 days and under 3000 miles. In that
one, the problem was an auxiliary horn had been installed and
grounded to the radiator support. So if a vehicle
recently had an electrical accessory installed (donít forget
anti-theft alarm systems), check the grounds.
Although the most severe
results occur if the part is bolted to the radiator or its
support (such as a radiator fan motor), the modern electrical
harness is so complex, the source could be something in the rear
(remember all those sport utility vehicles and minivans with
their rear HVAC systems).
What you should do is check the
voltage as each electrical device is turned on. Because the
radiator electric fans are a primary suspect, start with them.
Just remember that many vehicles have dual fan systems, and
testing just one fan isnít enough. On the typical setup, you can
trigger each fan with a jumper wire to ground the particular fan
relay. The relay is wired to the power-train computer on most
systems, so unplugging its connector and hot-wiring directly to
the fan motor may be a safer approach. Be sure to check the
coolant voltage with the engine cranking, as the starter ground
circuit is another strong possibility.
If a circuit seems to be
producing an unacceptably high stray voltage through the
coolant, as a follow-up test, try installing a jumper wire as a
second ground, to see if the voltage drops. If that works, check
the existing ground and if it seems to be good (or the voltage
reading doesnít improve after cleaning and tightening the
ground), make a permanent installation of a second ground wire.
Produced by the National Automotive Radiator Association (NARSA)
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