Jim Grant's Tech Tips
'99 Subaru, Radiator Electrolysis
Q:
What
tests can be done on a '99 Subaru with a suspected electrolysis problem
in the coolant system? I've had several radiator core replacements in
a short time frame. The coolant checks out good (pH balance/color etc.)
-
Walter T.
A:
There
is an electrolysis problem that is becoming the new haunting of today's
automobile. If electrolysis is occurring in the cooling system it can/will
cause rapid failure of the radiator or heater core. Electrolysis causes
a chemical reaction that involves an ion exchange between the radiator
or heater core and engine coolant. To state it simply, the coolant just
eats the metal of the radiator or heater until there is none left. There
are a couple forms of electrolysis that can occur in the cooling system.
The most common is due to bad/acidic anti-freeze, which most people have
a basic understanding of. The not so common electrolysis, but more deadly,
is an electrically induced electrolysis. This is where the vehicle's electrical
system causes a high rate of ion exchange in the cooling system that rips
through heater cores or radiators. To test for this condition you need
a digital volt meter. Start the engine and bring it up to about 2000 RPM.
With the cooling system at operating temperature and the coolant flowing,
connect the negative probe of the volt meter to the negative terminal
of the battery. Place the positive probe in the coolant at the radiator
and monitor the voltage. If you see .4 volts or greater reading on the
voltage meter the coolant has to be flushed or there is a ground problem
on the vehicle. If it is a ground problem you will most likely see the
voltage reading climb if you turn on electrical accessories. To correct
this condition will require inspection of the vehicle chassis/body and
engine grounds. You may have to install a ground wire on the heater core
and/or radiator to the battery. Electrically induced electrolysis in a
cooling system is a mean beast. But it can be easily tamed with diagnosis
and a good ground wire.
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