Coolant check w/multimeter

Status
Not open for further replies.
Joined
Feb 17, 2007
Messages
348
Location
West Coast Florida
Just saw this in my recent Handyman mag...

Check your coolant conductivity with a multimeter.
1. Start with cold engine
2. remove radiator cap
3. start motor
4. Set voltmeter to 'DC' (20 volts or less)
5. after reaching operating temp, insert positive (+) probe into coolant.
6. Rev engine to approx 2k and place probe onto negative (-) side of battery.
7. If the meter reads less than .4 volts your coolant is good.
8. readings above .4 volts the electrolisis additives are exhausted.

Anyone tries it please reply
thumbsup.gif
 
wait... how do you remove radiator cap, run engine to temp and perform this test without spilling a LOT of coolant on the ground, requiring more new coolant anyway?

Modern radiators are filled to the brim, if they have a cap at all (sometimes you need to use the overflow bottle, as that is where the pressure cap is).

I can see having the engine running, so the electrical system is in some state of operation... but operating temperature?!?!?

JMH
 
You could get away with it if you have a pressurized surge tank... but not a conventional overflow tank setup.

Checking coolant this way is an interesting idea... but I have my doubts about how practical it is. My old Corsica has a pressurized surge tank. It's filled with relatively new John Deere heavy duty antifreeze. I'm gonna go try this out.
 
Dunno the specifics on test, I just happened to grab mag on the way out the door while going on biz....I want to try but will need to wait until Friday. Just thought it was an interesting article
 
'94 Chevy Corsica, 3100 V6. Iron block/aluminum heads, aluminum radiator. John Deere heavy duty (green) antifreeze, drained & filled a month or two ago.

With the engine running at operating temperature, and surge tank cap removed, I put one lead in the coolant, and one on the negative battery terminal. Measured .10 V. Same measurement (.10 V) with the engine off, still at operating temp.

Just for laughs, I'll do the same checks with a cold engine.
 
Last edited:
Cuz as the coolant turns acid the different metals, Carbon if used in the rad hoses makes a battery . the less noble parts dissapear molecule by molecule.
 
After forgetting about it for a week or so, I did the test with the engine 'cold' (about 70 degrees F- sat overnight).

With the cold engine running, I get .10V. With the cold engine, not running, I get .14V from coolant to battery ground, but the voltage gradually drops to zero if I hold the multimeter leads in place for 30 seconds or so. Remove the leads and let it sit for a few minutes, and the .14v comes back.

So my tentative and unscientific conclusion is that the engine difinitely needs to be running for this test to be useful. Not sure if it needs to be warmed up... but that certainly isn't practical for a standard overflow system.
 
I got like .07 volts on my Roadmaster when I had it running today. Now as for the ranger, who knows it was reading in the negative volts for some reason. LOL I'll have to test my gf's car (fresh coolant) and my moms g6.
 
Hi.

When i checked for an electrolysis by attaching one test lead to the battery and the other into the cooling system,i read 0.7V at the voltmeter,but during 10 second the voltage,gradually,went down to 0.1V.(even when the engine was running).
Should it needs to stay on 0.7V in order to identified as a problem?
Since in my case it didn't stay on 0.7V,it was 0.7v for 2 seconds and started to decrease,gradually, to 0.1V?
What is it mean?
Thanks in advance.
 
But what does my results mean?
Is the decreasing of the voltage from 0.7v to 0.1v means that the coolant is good?
while it should stay constantly on 0.7v in order to show that it is not good?
 
I don't understand why the engine has to be running to do this voltmeter check. It's hard enough to do it with the engine running with the radiator cap off and not lose coolant. If any electrolysis were happening because of worn out coolant, I would be more confident of the validity and significance of the readings with the engine turned off since this is the state the engine is in most of the time.
 
Originally Posted By: xchcui
But what does my results mean?
Is the decreasing of the voltage from 0.7v to 0.1v means that the coolant is good?
while it should stay constantly on 0.7v in order to show that it is not good?


The reading should stay at the same level. I've never seen nor heard of progressively decreasing voltage as the seconds tick by. Are you using a good quality digital multimeter?
 
Originally Posted By: berniedd
[/quote]

The reading should stay at the same level. I've never seen nor heard of progressively decreasing voltage as the seconds tick by. Are you using a good quality digital multimeter?

Yes,i have been checked it with 3 different voltmeter.
 
I'm getting .2 volts in the coolant with the engine running. The negative probe in the coolant and positive probe of the multi meter on the negative ground of the vehicle to show a positive reading on the meter. It slowly bleads down with the engine shut off.
I'm not sure why I had to put the meter opposite of what the OP said.
It's holding at .110 volts after five minutes shut down.
 
Status
Not open for further replies.
Back
Top