A prior search of: coolant electrolysis, yielded three threads, now there are four.

Does anyone know the typical values and upper limits for the voltage measured between the coolant and ground?

ASTM suggests 0.3VDC - 0.5VDC as reasonable.

Ford has a TSB out with an upper limit of 0.4 VDC.

Some radiator and heater core vendors like no more than 0.1VDC.

If anyone wants to contribute the readings from their own vehicle, the method is:

using a DVM (digital voltage meter),
measure the voltage between coolant at the coolant tank
and ground using the DVM probes,
without contacting the coolant tank.

for this thread, measurements should be taken with engine off, and engine on.

Please note which is which, and the age and type of coolant you are running.

To help reporting, here is a blank template:

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engine off VDC:
engine on VDC:
coolant type:
coolant age:
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