Fox Is it time to replace the coolant?

PonyGTrider · Sep 16, 2025

Hi all,
By accident I tasted a bit of coolant from my 306 engine and it was extremely acidic.
Reading around I found articles about testing the coolant condition using a DVM. I followed the instructions turning the volt meter on to VDC placing the red lead into the coolant in the radiator and the black lead to a good ground. I got a reading of -0.200 Volts but the minus indicates me it is inverted polarity. I then exchanged the leads and then I got the correct 0.200 Volts the articles said you should have 0.400 V or less to be good.

I google this anomaly and the suggestion I received was that my coolant has to be replaced as soon as possible.
I have an aluminum Griffin radiator and a magnesium sacrificial rod hanging inside the rad cap.
Can anyone share an opinion on this one?
I will certainly appreciate it

Noobz347 · Sep 16, 2025

How long has the coolant been in there?

What type of coolant did you use (classic green)?

I have always used these things:

But I hear rumor that these are better?

Amazon.com

nickyb · Sep 16, 2025

When in doubt , Drain it out.
Use distilled water to mix with coolant.

PonyGTrider · Sep 16, 2025

Noobz347 said:
How long has the coolant been in there?

What type of coolant did you use (classic green)?

I have always used these things:

But I hear rumor that these are better?

Amazon.com

Actually my coolant is old, I use the typical Preston green at 32% concentration. Never had any overheating problems.
Now that you mentioned it I have the second coolant tester you posted I will use it right now.

Thanks for your ideas

nickyb said:
When in doubt , Drain it out.
Use distilled water to mix with coolant.

Noobz347 said:
How long has the coolant been in there?

What type of coolant did you use (classic green)?

I have always used these things:

But I hear rumor that these are better?

Amazon.com

I just used the coolant tester and either it is not good or something else is gong on.
Thanks second photo shows what the coolant in the engine looks like and apparently it is shot. But, the first photo shows what a brand new coolant out of the bottle 50/50 looks like… it reads the same! So is my tester bad or what is going on???

nickyb · Sep 16, 2025

I have always bought full strength coolant and a gallon of distilled water, mixed 50/50 and call it a day.
This has gotten me 316,000 miles on my stang, so ill stick with what has been working.

PonyGTrider · Sep 16, 2025

nickyb said:
I have always bought full strength coolant and a gallon of distilled water, mixed 50/50 and call it a day.
This has gotten me 316,000 miles on my stang, so ill stick with what has been working.

I’ve always used Preston 32% ready to use without any issues.
I was just wandering why I have reversed polarity when using a volt meter.

General karthief · Sep 17, 2025

Is it because of the 'reverse rotation' water pump
Asking for a friend

nickyb · Sep 17, 2025

Could be his magnetic personality.

AeroCoupe · Sep 17, 2025

Flip the leads on the DVM….

PonyGTrider · Sep 17, 2025

AeroCoupe said:
Flip the leads on the DVM….

I did that, my question is why is that? The coolant supposed to be positive voltage…
Thanks anyway

Noobz347 · Sep 17, 2025

Where did this idea come from that you measure voltage in your coolant?

Off the top of my head, I can think of a dozen things that could effect this method.

RaggedGT · Sep 18, 2025

Aluminum radiator?

nickyb · Sep 18, 2025

Noobz347 said:
Where did this idea come from that you measure voltage in your coolant?

Off the top of my head, I can think of a dozen things that could effect this method.

Maybe the band he's in started playing different tunes.

General karthief · Sep 18, 2025

I remember from the past something about an electrical charge when liquid is pumped through different metals bolted together like a timing cover to block that is referred to as 'electrolysis ' I believe but I think it can't be measured by a common DVM, maybe measured in seized bolts in a typical block.
Then again I may be just rambling

Noobz347 · Sep 18, 2025

General karthief said:
I remember from the past something about an electrical charge when liquid is pumped through different metals bolted together like a timing cover to block that is referred to as 'electrolysis ' I believe but I think it can't be measured by a common DVM, maybe measured in seized bolts in a typical block.
Then again I may be just rambling

Yeah but.... The material your radiator made from would have an effect. The material your heater core was made from, etc...

Anything under half a volt on your average Walmart voltmeter is kinda suspect. It is not uncommon to see full 1 to 2 volt swings on some meters.

Is seem like it would be more telling to measure the resistance of a coolant sample but even that doesn't account for metal contamination.

AeroCoupe · Sep 19, 2025

My comment on swapping the leads was a joke.

When you guys come up for air from this deep hole of "not gonna make a damn bit of difference" let us know. If the fluid checks good with a hydrometer and is not discolored move on down the road.

gkomo · Sep 19, 2025

Why not just change the fluid to be safe? Pretty cheap to do and easy if you have one of those coolant fill tubs that connects to your radiator fill port.

General karthief · Sep 19, 2025

I just strain my coolant through an dirty sock and top it off with full strength green....

Noobz347 · Sep 19, 2025

General karthief said:
I just strain my coolant through an dirty sock and top it off with full strength green....

Once again, this is your recipe for coffee and not coolant.

They just taste the same.

FastDriver · Sep 19, 2025

lmao... WTF is this whole conversation?! lol I mean, lord knows I'm all for overthinking everything, but if I didn't like the look, smell, taste, feel, or sound of my coolant, I'd just replace it. Would take as much time as reading this thread did... except for the annoying air pockets.

Fox Is it time to replace the coolant?

PonyGTrider

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

nickyb

I gotta say i never painted my nuts, Never Ever

PonyGTrider

Attachments

nickyb

I gotta say i never painted my nuts, Never Ever

PonyGTrider

General karthief

wonder how much it would cost to ship you a pair

nickyb

I gotta say i never painted my nuts, Never Ever

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

RaggedGT

Been here over a DECADE and still no CT

nickyb

I gotta say i never painted my nuts, Never Ever

General karthief

wonder how much it would cost to ship you a pair

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

gkomo

now i can hopefully expect to receive the shaft

General karthief

wonder how much it would cost to ship you a pair

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

FastDriver

I was uncomfortably high & wearing a helmet

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Fox Is it time to replace the coolant?

Stangnet Facilities Maint Tech... Er... Janitor

I gotta say i never painted my nuts, Never Ever

Attachments

I gotta say i never painted my nuts, Never Ever

wonder how much it would cost to ship you a pair

I gotta say i never painted my nuts, Never Ever

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

Been here over a DECADE and still no CT

I gotta say i never painted my nuts, Never Ever

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

I was uncomfortably high & wearing a helmet

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