pH of my coolant

[Kestas]

I tested the coolant on three of my cars. All have been in service for roughly 2 years with low miles. Here are the numbers:

pH------miles-----antifreeze-------vehicle
9.8 ------2K-----(green stuff)----71 Cutlass
10.1-----10K-----(green stuff)----91 Marquis
7.5------10K-----(dealer)---------95 Mercedes

I believe the aim should be for a pH of 9 or 10. Anything below 8 should be changed out. Demineralized water was used for the makeup.

I'm curious why the pH of the dealer coolant (identical to Zerex G 05) in the Mercedes dropped so much.

I'm inclined to leave the green coolant in those vehicles, regardless of the time. It hasn't been used up yet.

 

[Ken2]

Some antifreezes, mainly Japanese and maybe others, are close to pH 7 when freshly mixed 50/50.

I use my voltmeter to tell when the coolant has lost enough corrosion inhibitors to need changing. Put one probe on the battery negative terminal and the other probe in the cool coolant, not touching any metal. If you read about 0.1 volts DC, good. If you're up to 0.3 or 0.4 volts DC, time to change.


Ken

 

[Big Jim]

OAT (and HOAT) coolants start life with a lower PH. Since the OAT doesn't break down as rapidly, they do not need as much reserve alkilinity.

I don't know what a good PH reading would be for the HOAT in your Mercedes, but I know that it would be lower than old style conventional green.

If I had the ability to measure the PH in my Escape (also uses G05) to see if it would provide any insight.

 

[dkcase]

quote:

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Originally posted by Ken2:


.... Put one probe on the battery negative terminal and the other probe in the cool coolant, not touching any metal. If you read about 0.1 volts DC, good. If you're up to 0.3 or 0.4 volts DC, time to change.


Ken

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I admit I haven't tried it yet, but why the negative terminal at the battery ? Seems like you would be trying to test a circuit through the fluid, and assuming the better circuit = the worse coolant condition. Since the fluid is in contact with the radiator / block , and in turn with the chassis, what is the source of the small voltage I am looking for ?

 

[Ken2]

The source of the voltage is galvanic action of the dissimilar metals in the engine and radiator with the coolant serving as an electrolyte.

You can determin initial pH by mixing some antifreeze 50-50 with pure water and testing that.


Ken