Suitable coolant / Corrosion inhibitor.

[Lynn Eades]

The first thing I found on the net:

If you think the only job of antifreeze (coolant) is to cool the engine during the summer and prevent freeze-up during the winter, read on. Coolant also plays an important role in preventing corrosion caused by electrolysis. Electrolysis occurs when two dissimilar metals start swapping electrons, causing the metals to corrode. Since an engine has aluminum, copper, cast iron, steel and magnesium alloys, electrolysis will slowly eat away at its innards.

Coolant has additives to prevent all of that electron swapping. But, as coolant ages, the additives are depleted and can’t do the job anymore. In fact, worn coolant becomes a pretty darn good electrical conductor, accelerating internal electrolysis. The good news is that it’s pretty easy to check the conductivity of your coolant with a digital multimeter. If the conductivity is high, it’s time for a coolant flush and fill. Here’s a quick way to check it.

Begin with a cold engine. Remove the radiator cap and start the engine. Set your digital multimeter to DC volts at 20 volts or less. When the engine reaches operating temperature, insert the positive probe directly into the coolant. Rev the engine to 2,000 rpm and place the negative probe on the negative battery terminal. If the digital meter reads .4 volts or less, your coolant is in good condition. If it’s greater than .4 volts, the electrolysis additives are exhausted, and you may be in the market for a new radiator, a water pump or a heater core in the future. All of those are far more expensive than a simple coolant change.

[Lynn Eades]

A different angle:

By Ralph Kalal

You knew you had to worry about the freeze protection offered by antifreeze. But, do you need to worry about your coolant’s pH, as well?

Many mechanics claim that testing the pH level of antifreeze is an effective way of determining its condition. Some professional repair shops offer additives ostensibly intended to insure a proper pH in your antifreeze.

Here’s the pitch: water has a pH of 7.0 and antifreeze has a pH of 10.5, so a 50-50 mix has a pH of 8.75, and that’s too acidic to protect the cooling system, so the pH must be modified to something around 10 to protect the dissimilar metals in the modern cooling system. And, further, antifreeze must be frequently replaced to ensure proper pH.

The pH value is a way of expressing the relative acidity of coolant. Acidity does cause corrosion. There are even reported instances of old coolant becoming so acidic that it turns the entire engine into, in effect, a battery, affecting electronic engine controls.

Look closely, though, and you’ll notice that the typical pitch for replacing antifreeze (because it has the wrong pH) simply equates the pH of water to the pH of conventional green ethylene glycol antifreeze at a 50-50 mix, and then claims that the resulting number is too acidic.

That comparison ignores the corrosion resistant formulations built into modern antifreezes, especially the Dex-Cool and G-05 long-life formulations. These antifreezes are designed to have a lower pH than conventional ethylene glycol antifreezes; 8.3 compared with 10.
Test strips that can be dipped into the antifreeze to determine the pH level are available at auto parts stores, if you want to check your antifreeze’s pH level.

With but one exception, it is not a good idea to supplement Dex-Cool or G-05 with additives, even those claiming to be compatible with those products. The corrosion-resistant capabilities of OAT antifreezes are the result of its organic chemical structure, the same chemical structure that delivers its freeze protection.

The sole exception is when the manufacturer says to put something else into the antifreeze solution, as specified in either the owner’s manual or the factory shop manual, in order to address a specific coolant concern. Cadillac, for example, specified the addition of “coolant tablets” to antifreeze in pre-2000 Northstar engines to eliminate a porosity problem with the aluminum engine block casting that could lead to coolant leaks.

Last, but certainly not least, is whether the antifreeze in your car offers adequate protection against freezing. You can test this.

There was a picture here, of an antifreeze hydrometer, which doesn't come through with the "copy and paste"

Test it with a “coolant hydrometer” available at any auto parts store. This inexpensive device measures the specific gravity of the coolant. It does not, however, tell you anything of the corrosion protection capabilities remaining in the coolant. Simply insert the tip of the hydrometer into the antifreeze and pull some into the chamber, enough that the float lifts free. The reading tells you the freeze protection.

[Lynn Eades]

And then on You tube:

https://www.youtube.com/watch?v=mBXZtfzHhig

[Rob Beale]

pH means Hydrogen Index. It is a German language term, like ABS!

The pH scale measures the acidity or alkalinity of a substance on a scale from 1 to 14
pH 1-2 is extremely strong Acid, pH7 is neutral and pH13-14 is extremely strong Alkali
Examples of the 3 are stomach acid, distilled water and Caustic soda.

Note that rain water is slightly acidic due to dissolved CO2 from the atmosphere about pH5.5

Coke is about pH3.5 which works like other acidic rust converters.

Baking soda is weak alkaline, and is good for neutralising acid spills on car batteries and terminals.


My reading of the quotes from Lynn is that we want stronger alkaline pH levels in our engines

Cheers
Rob

long retired science teacher!

[Lang]

You need to remember with Glycol (and many other additives) the cooling efficiency is greatly reduced over plain water and the increased boiling point is required. There is a considerable difference in temperature in an engine running additives and one running plain water under the same conditions.

Modern engines like a bit more heat to run efficiently but the old ones like their 180 degrees. So we now have high pressure radiator caps and high boiling point additives including the anti-corrosion ones necessary in alloy engines particularly.

Lang