I am not really new to working on cars since I have over 45 years of working on cars under my belt. Many years ago I used a volt meter to test antifreeze but for some reason I stopped and never used the test again. Below is some info I grabbed off Google about it. What I am looking for are some test results from you guys on your Z's and whatever else you have to test. I tested a S15 JIMMI I have and it was high as was my 71Z. I think my Z has a ground issue that is causing the high reading. The JIMMI was dead antifreeze but the high reading is what I think caused a freeze plug to leak and the steel back plate of the water pump to leak. This weekend I will tackle the Z to see what is causing the high reading.

Checking antifreeze with a volt meter

Googled this and found its a great test procedure. Bad grounds

can cause the readings below, as well as dead anti rust/corrosion

inhibitors. once the readings go high all kinds of nasty things happen.

Electrolysis of the radiator. soft plugs to name a few.

What is Electrolysis?

As the additives in your coolant that keep it neutralized become

depleted the coolant actually develops an electric charge from

passing over dissimilar metals. You can even measure this voltage

with a voltmeter! This small electric current removes metal from

engine surfaces leaving large pits or holes and can eventually

eat entirely through a component. It can also weld bolts and

fittings to the engine and components.

The American Society for Testing and Materials (ASTM) did testing

with hydrometers and deemed that the majority of hydrometers are

inaccurate. as a result of this, they removed hydrometers from the

approved methods list for testing coolant. stray current testing is

a good indicator

Then there is PH testing with the`test strips.

Just Google antifreeze PH testing and see for yourself. It does

look interesting

These are the common readings off the web

Negative digital volt meter lead to battery negative, positive in

radiator cap touching only coolant.

0.2 V to 0.5 V - antifreeze is still good

0.5 V to 0.7 V - antifreeze is borderline

0.7 V or greater - antifreeze is unacceptable.

Edited September 15, 201014 yr by Maples71240Z

When in doubt drain it out and replenish. That way you know exactly what you've got, no guessing.

When in doubt drain it out and replenish. That way you know exactly what you've got, no guessing.

That is true with my JIMMI since it has been a while since it had a coolant change and now the reading is .14 Volts. But the Z was changed a couple months ago and it reads .57 Volts and that reading drops when the battery is disconnected.