Testing Coolant with Multimeter?

[Guest]

I know it is possible to test the condition of coolant with litmus paper, but this bloke claims to do a PH test with a multimeter. Fact or fiction?
 

 

[RLWP]

https://www.edn.com/design/test-and-measurement/4340776/Convert-your-DMM-to-a-pH-meter

 

That tells you how to do it, which isn't what the video shows

 

Richard

[1st ade]

Don't know about Ph but I guessit's forming a battery between the copper probe of the meter and the steel of the engine block with the coolant as an electrolyte? High voltage means it's a "good" electrolyte?

[WotEver]

There are several sites that say the same as the video in the OP.  I’ve not seen any that suggest it doesn’t work although why the coolant would be generating 20mV is beyond me. 

1 minute ago, 1st ade said:

High voltage means it's a "good" electrolyte?

Which means that the inhibitor is bad. 

[1st ade]

1 minute ago, WotEver said:

Which means that the inhibitor is bad. 

So he's kind of got the right answer (if for the wrong reason)? - High voltage = change coolant

[Guest]

Not sure myself. There are similar claims for testing brake fluid too (not that there is a great call for that in boats )

Edited March 12, 2019 by Guest

[David Mack]

4 minutes ago, catweasel said:

Not sure myself. There are similar claims for testing brake fluid too (not that there is a great call for that in boats )

Ah! Maybe that's why my boat won't stop on a sixpence!

[WotEver]

5 minutes ago, 1st ade said:

So he's kind of got the right answer (if for the wrong reason)? - High voltage = change coolant

Yes, but I don’t understand the mechanism by which it works. Another website says that on the 20V range you don’t want more than 0.4V whereas he says no more than 0.04V. It’s all a bit odd. 

[Guest]

8 minutes ago, WotEver said:

Yes, but I don’t understand the mechanism by which it works. Another website says that on the 20V range you don’t want more than 0.4V whereas he says no more than 0.04V. It’s all a bit odd. 

I noted same. Also there are several types of coolant which may behave differently?
I will definitely try a before and after test next time I change coolant though, for the minute it will take. Perhaps a rough guide?

[OldGoat]

What's wrong with using an hydrometer? - Use the KISS principle

[Wanderer Vagabond]

3 minutes ago, OldGoat said:

What's wrong with using an hydrometer? - Use the KISS principle

Does the hydrometer tell you whether or not the inhibitor in the coolant is shot? I thought it just told you whether the dilution was right or not.

[Guest]

7 minutes ago, OldGoat said:

What's wrong with using an hydrometer? - Use the KISS principle

That is fine for coolant strength/ratio, but the PH is a different concern. Incorrect PH eats the engine/cooling system metal parts. Litmus paper is another method, again simple.

Edited March 12, 2019 by Guest

[dmr]

Various anti-freezes use very different chemistries for the anti-rust function? I wonder if they all have enough in common to make this a reliable test?

 

...............Dave

[Guest]

3 minutes ago, dmr said:

Various anti-freezes use very different chemistries for the anti-rust function? I wonder if they all have enough in common to make this a reliable test?

 

...............Dave

IIndeed. 

[BEngo]

The simplest test for coolant comes in two parts:

Shove a sample in the freezer in a plastic pot.  If it goes solid you need more/new antifreeze. 

When the sample has melted drop 2 or 3 ordinary nails or steel panel pins in it.  If they go rusty after a couple of days the corrosion inhibitor is worn out.  Either add new inhibitor (Screwfix or DIY shed central heating area), checking it is OK for aluminium heat exchangers if you have an alloy engine, or renew antifreeze.

 

N

[Guest]

1 hour ago, BEngo said:

The simplest test for coolant comes in two parts:

Shove a sample in the freezer in a plastic pot.  If it goes solid you need more/new antifreeze. 

When the sample has melted drop 2 or 3 ordinary nails or steel panel pins in it.  If they go rusty after a couple of days the corrosion inhibitor is worn out.  Either add new inhibitor (Screwfix or DIY shed central heating area), checking it is OK for aluminium heat exchangers if you have an alloy engine, or renew antifreeze.

 

N

I had heard of the freezer trick, but the nail idea is good. Might give that a go.

[Guest]

Further to this, it is a nice day so out came the multimeter and Chinese litmus paper.
Both engines cold and not running.

 

My car has 12 year old antifreeze in it (should have been changed at 10 yrs.) Readings 0.2 Volts ph 9.

Boat two year old antifreeze (blue stuff). readings 0.09V ph 9.

I think ph9 is considered safe?

ps can somebody please remind me what the additive is called that gives the coolant an extra corrosion-protection life? Think it begins with an "A" 
Cheers.

[ditchcrawler]

5 minutes ago, catweasel said:

Further to this, it is a nice day so out came the multimeter and Chinese litmus paper.
Both engines cold and not running.

 

My car has 12 year old antifreeze in it (should have been changed at 10 yrs.) Readings 0.2 Volts ph 9.

Boat two year old antifreeze (blue stuff). readings 0.09V ph 9.

I think ph9 is considered safe?

ps can somebody please remind me what the additive is called that gives the coolant an extra corrosion-protection life? Think it begins with an "A" 
Cheers.

So if the ph is the same what did you deduce from the voltages?

[Guest]

9 minutes ago, ditchcrawler said:

So if the ph is the same what did you deduce from the voltages?

As they are quite different, not a lot!
They  are however under the 0.5V that some argue is the limit. I am having some doubts about the test, probably because an elderly designed stationary engine will have very different metals to a ford Zetech? 
In a couple of weeks the car will be  going for a flush and new coolant so just for the hell of it I will measure again and take pH. 

[ditchcrawler]

1 minute ago, catweasel said:

As they are quite different, not a lot!
They  are however under the 0.5V that some argue is the limit. I am having some doubts about the test, probably because an elderly designed stationary engine will have very different metals to a ford Zetech? 
In a couple of weeks the car will be  going for a flush and new coolant so just for the hell of it I will measure again and take pH. 

I await you results.

 

[Guest]

On 31/03/2019 at 16:22, ditchcrawler said:

I await you results.

 

Just done the test with new antifreeze in car and allowed it to settle for a few days. Same stuff (ford pink) same strength and cold engine.

Voltage still in region of 0.2 but ph shifted to 7
I suspect that this 10 year antifreeze will see my long suffering car out (unless something bursts of course) so i won't be bothering again

Will be keeping an eye on the boat readings though, just out of curiosity (it killed our cat.)

[RLWP]

4 minutes ago, catweasel said:

Will be keeping an eye on the boat readings though, just out of curiosity (it killed our cat.)

And weasels?