Need some expert comment about coolant

A mechanic that works on my S2000 routinely does conductivity testing on the coolant of cars he services. My 2003 with 38K miles tested 0.2 Volts on his meter. His standard for power flush and replacemnt is 0.4 Volts. I'll probably flush at 60K regardless.

I did question him about conductivity testing in general and I'm wondering about the correctness of his response. One reason he stated is that the concentration of ionic compounds builds up as coolant ages, and that's bad. Second, he claims that small metal particles from engine surfaces accumulate in coolant, and those are abrasive to instruments in the system (temperature probe, ??), and that the load of these can be estimated with conductivity testing. That last part, especially, has me wondering. Even if small metal particles do build up, how could conductivity testing detect that? I would think that conductance would require ions in solution and that metal particles would have to be so thick as to be practically in contact between the electrodes to increase conductance.

What's the truth about conductivity testing? Does any of this really apply to our cars?

Thanks!

Steve

 

yes, conductivity does apply to coolant testing. the rest of your questions are over my head.

 

You have a model year 2003, which uses Honda Type II engine coolant. This fluid is considered good for 10 years or 120,000 miles.
Do a hydrometer test to see what its freezing point protection and boiling point protection is. Although I wouldn't wait 10 years or 120K miles if it were my car, keep checking it annually till you get to about 6 to 8 years (100K), then change it if you see the freezing/boiling points change. I think in this respect, Honda made a pretty "low maintenance" car.

 

The hydrometer test showed good to -30 deg F, which means the freezing/boiling properties are OK. Its already established that my coolant is fine. I also know what my owners manual says.

The mechanic's assertion was that the manufacturers don't consider other things that affect cooling system health when writing maintainence schedules and that conductivity testing can reveal other factors that would suggst a coolant changeout is warranted. He named a few of those factors, but he's not a chemist and couldn't explain it as well as I wanted. I'm just trying to understand more about the subject.

I did some internet research and none of the web sites I found said anything about metal particles and didn't say much about the consequences of conditions causing "high" conductivity, except some stuff about precipitates. I know enough to avoid silicates and phosphates so the value of conductivity monitoring for long-life coolants still has me wondering.

Steve

 

Does he do this test while it is running? I think in order to get the correct reading of actual metal parts in the coolant you would need to insure it is spread through out the fluid pretty good. What im saying is, what if all the metal was on the bottom of lets say the radiator at the time he puts his multimeter probes in?

 

We have a few chemical engineers in our midsts. Hopefully one of them will pick it up. In the meantime I have PM'd one of the chemical engineers who posts here, and hopefully he'll respond.

 

[QUOTE=sstodvictory,Apr 27 2006, 03:56 PM] Need some expert comment about coolant

A mechanic that works on my S2000 routinely does conductivity testing on the coolant of cars he services.

 

Thanks jrfish007.

 

I doubt that you really have metal particles circulating in your cooling system, but theoretically...

...you can imagine a circuit between the test meter probe points, partly made up of coolant and partly made up of metal particles. The conductivity of the particles is comparatively very high, and the space they take up shortens the path through the coolant. The conductivity of the coolant is reduced because of the shorter path through it, leading to an overall increase in the conductivity reading.

I believe this is a physically correct explanation of a very improbable situation.

 

"For a metal it is either touching and it is conductive or it is not."

You are assuming that air is not conductive. This is not precisely true, if the voltage is high enough, air (and many other 'insulators') becomes conductive (not that I think that this is necessarily relevant at the voltages in the test) hence lightning and spark plugs existing.