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edlithgow
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PostSubject: Coolant Testing   Fri Mar 13, 2015 7:29 am

This MIGHT be better in "tips", but its a bit "experimental"

I bought the car (1986 Daihatsu Skywing, like Charade G11) in April 2010 so the coolant is at least 5 years old (was apparently dealer-serviced by-the-book by the previous owners so probably not THAT much older). I donít know what was in it but its probably overdue for a change.

The coolant visible in the radiator is green, but I donít know what type or brand it is. Anti-freeze of course isnít a requirement here in Taiwan, but corrosion protection is.

Allegedly you can test for electrolytic corrosion with a multi-meter.

Some online references (there are also youtube videos but I didnít bother with them, a word being worth a thousand redneck-illiterate pictures)

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This one wants you to test it running (2000 rpm) at normal operating temp, (impossible?)

< 0.4 Volts OK > 0.4 Volts BAD (which is plainly an arbitary cutoff)

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- lead to ground + in the coolant (rad)
- <0.1 Volts OK
- >0.3V BAD
- > 0.3 V with battery disconnected = ďType AĒ(self sustaining) electrolysis.
-
- FLUSH and change. A range of flushing techniques/chemicals is discussed/pitched
-
- 0 volts with battery disconnected = †ďType BĒ (earth leakage) electrolysis due to a bad ground/current leakage to earth Ė locate and fix.

It seems that the engine is OFF for these tests, though it isnít explicitly stated.

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Similar numbers, and they want the engine at 2000 rpm testing for current leakage, but donít say it has to be at temperature.

They suggest using a bit of copper tube on the + electrode in the coolant.

They also suggest testing the alternator for overcharge (>14.7 volts), and using pH strips, specific test strips, a hydrometer or a refractometer, and pitch a range of chemicals and gadgets.

I had/have a refractometer in the UK, though it was designed for sucrose solutions so I dunno if itíd work with coolant.

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Conflicting numbers

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ACDelco say <0.3V. They deprecate hydrometers, apparently due to lack of temperature compensation.

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Forced electrolysis experiment, essentially testing the performance of coolant mixtures as electrolyte Ė not sure how relevant this is to real-world in-car situation.

Testing on the Skywing, voltage was initially about 0.14 volts but fell quite quickly to about 0.09V, and continued to fall more slowly thereafter. Subsequent re-tests started about 0.9V and fell (will have to look again to establish a rate). Ignition/fan/lights on didnít seem to make any difference.

I didnít try running the engine.

This doesnít give particular ground for concern, (though the instability of the voltage reading isnít mentioned in any of the refs.) but Iíll be changing it anyway once I decide what to use.

RT-Mart had Peak, an American product, with labelling in English, so Iíll probably go for that. Everything else was in Chinese.
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Justwatching
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PostSubject: Re: Coolant Testing   Mon Mar 16, 2015 4:52 am

I use multiple different tests on the assumption that multiple false readings in the same direction from independent measures are unlikely, thus, if all agree the coolant is good, I can trust it. I use a hydrometer, PH meter and DVOM test as you mention (I use the 0.3v cutoff). I also use a visual inspection as a necessary-but-not-sufficient standard, in so far as, if the coolant is visually rusty with particles floating round, I'd disregard any differing result and change it.

I personally like to let the evidence speak. If all indications are saying the coolant is good, I'd leave it for now and review again later.
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edlithgow
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PostSubject: Re: Coolant Testing   Tue Mar 17, 2015 4:27 pm

Justwatching wrote:
I use multiple different tests on the assumption that multiple false readings in the same direction from independent measures are unlikely, thus, if all agree the coolant is good, I can trust it. I use a hydrometer, PH meter and DVOM test as you mention (I use the 0.3v cutoff). I also use a visual inspection as a necessary-but-not-sufficient standard, in so far as, if the coolant is visually rusty with particles floating round, I'd disregard any differing result and change it.

I personally like to let the evidence speak. If all indications are saying the coolant is good, I'd leave it for now and review again later.

I currently only have visual (looks OK from the rad cap) and the voltage readings. (That 0.9V above should of course be 0.09V)

While these (and the other parameters) are represented as indicators of coolant breakdown (so "bad" readings indicate a change) I'm not sure that "good" readings necessarily mean its OK.

"Standard" recommendation is a 2-year service life, with some of the "long-life" stuff at 5 years, so best guess is this fills been in 3X longer than the (admittedly probably conservative/product-shifting) recommendation.
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