Dexcool Test

[Scotty]

I was just looking through my bookmarks and found this on Dexcool, what got my attention was the voltmeter test to determine the condition of the Dexcool. Anyone ever see this test? What do you think? You engineers out there why would the voltage passed change if the Dexcool was going bad or bad?

http://www.getahelmet.com/jeeps/maint/dexcool/

Here is an exerpt

As for deciding when to change your antifreeze, don't go by miles or you WILL certainly have seal and mechanical failures. One interesting spec I found is to use a multimeter. You put your negative probe to the negative post on your battery. You then place the positive probe in the neck of your radiator, making sure that the positive probe touches nothing but the antifreeze. Make sure the coolant is warm but not HOT (this is for SAFETY reasons as well as accuracy of your readings. Always be careful when opening the radiator cap on a warm engine). Your readings (regardless of negative symbol on readout) should be:

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.

Things that make you go, HMMMM! I will be out with my voltmeter in the morning!

This is a JEEP web site, would these readings change for our Northstars? Would measuring the voltage at the tank make a difference? It sounds like there are a lot of variables to consider

[adallak]

Scotty,

While it is not difficult to find a reason why the resistance of the coolant changes (it is an electrolit) I do remember our guru saying that the test was not reliable.

[Ranger]

Scotty,

While it is not difficult to find a reason why the resistance of the coolant changes (it is an electrolit) I do remember our guru saying that the test was not reliable.

I remember that as well. .

[Matt]

Hey Scotty, that sure is interesting. Even though it is late I started to head for the work shop to get the Ohm meter when my girl came out from the other room. Talk about things that make you say HMMMM, that test is going to have to wait for the AM. Good Night Guys

[TDK]

Folks,

This subject was discussed some weeks ago and with a person much sharper than me. But here is a bit of what I recall:

There are a number of sites that use "conductivity" as a key parameter in determining coolant changes and also for coolant recycling etc.

Voltage probes are simply not the way to reliably measure conductivity. There may be some correlation, but a conductivity probe is very similar to a pH probe - in that temperature makes a big differance and it needs to be calibrated etc.

Even so, conductivity is simply an overall measurement of what else might be in the coolant. But this only means anything - if you measured it at first fill and every so often. And it still only means there is more stuff in the coolant (not good stuff or bad stuff - just stuff).

This measurement can be affected by a number of factors that might have nothing to do with the coolant being any good or not

Recyclers use this measurement as one way to determine how "clean" a given coolant is during the filtering or whatever process (some real fancy ones out there now).

Like I noted earlier, search on "coolant + conductivity" over 30-days.

Good luck

[Scotty]

I recall speaking about this vaguely. But don't recall the parameters that I found. Was thinking that depending upon the coolant temp the voltage could vary. I am surprised that the voltage is not taken at a specific temp. I could not remember what out expert said, and a search was not helpful.

[adallak]

I recall speaking about this vaguely. But don't recall the parameters that I found.  Was thinking that depending upon the coolant temp the voltage could vary.  I am surprised that the voltage is not taken at a specific temp.  I could not remember what out expert said, and a search was not helpful.

Scotty,

Our expert did not explain much, just said it was not reliable. Now we all have to rely on our memory...

[JimD]

....Your readings (regardless of negative symbol on readout) should be:

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....

I have not attempted this measurement and maybe some folks reading this will surprise me and report a variety of readings. A decent modern Digital VOM is a very sensitive and accurate device but the operator has to understand what is being measured. My Fluke VOM will show me 0.125 VDC with one lead touching my left hand and the other lead touching my right hand.

Presence of a voltage indicates there is electrolysis. Electrolysis requires an electrolyte. Electrolytes are acidic.

You do not want an electrolyte in your cooling system. One of the measures of a 'long-life' antifreeze is the reserve alkalinity in the corrosion inhibitor package that prevents the mixture from becoming acidic. No acid = no electrolyte.

If you are able to obtain any consistent, repeatable voltage reading somehow, be sure to drain that coolant immediately and refresh the corrosion inhibitor package by adding fresh DexCool and distilled water. And then do it again 1,000 miles later.

[adallak]

Electrolits are solid state or liquid substancies which have ione conductivity unlike say, metals. They are not limited to acids.

[KevinW]

Presence of a voltage indicates there is electrolysis.  Electrolysis requires an electrolyte.  Electrolytes are acidic.

You do not want an electrolyte in your cooling system.  One of the measures of a 'long-life' antifreeze is the reserve alkalinity in the corrosion inhibitor package that prevents the mixture from becoming acidic. No acid = no electrolyte.

I didn't know a sodium chloride solution is acidic!

If you do not want an electrolyte in your cooling system, I suggest you use pure water, and change it regularly in case it dissolves anything. Let us know how long everything lasts.

The idea of using a DVM in that fashion to assess the quality of a solution of organic acids is laughable.

[jhall]

You can not use a digital voltmeter to perform conductivity measurements. This is equivalent to licking the terminals of a used 9V battery to determine how much voltage it can produce.

Conductivity meters use a measuring cell that has electrodes with a specific surface area placed at a specific distance apart. Additionally, these meters use AC power from the instrument to make the measurements at the cell (e.g. 85Hz to 1kHz).

There are hundreds of reasons for changes in conductivity of solutions that circulate through systems, so simply measuring the liquid does not do any good.

Understanding the reason for the change in conductivity is what you need to know, but it's cheaper to buy new antifreeze rather than acquiring the instruments to do this!