OT, engine coolant re-use

Does anybody have experience with testing and re-using engine coolant?

After a very long time I need to pull the radiator out of my Scout, get it fixed (leaky solder joints mostly) and refill. The old coolant (conventional green Prestone) looks reasonably good. The radiator is clean inside, the coolant is clear. Specific gravity is low.

New coolant is more expensive than I remembered, and getting rid (legally) of the old stuff is harder than it used to be. Simply adding more antifreeze to make the specific gravity correct is trivial, but I wondered if there might be more sophisticated tests to detect more subtle problems like pH. The original mix used distilled water, so total dissolved solids are likely to be OK. The major worry is the state of the corrosion inhibitors. Ordinary pH test papers are subject to cross sensitivity, so it'd have to be checked for use with coolant. Web searches for coolant testing found only specific gravity testers, nothing about pH or other chemical tests.

Thanks for reading, and any stories!

bob prohaska

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bob prohaska
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My '86 Toyota came with red coolant.

I used tap water when I replaced the red with green. From Santa Clarita Water Co., shittiest water in the Antelope Valley.

The Toyota's aluminum cylinder head apparently didn't appreciate having green coolant, or the shittiest tap water in the Antelope Valley.

I should have stuck with Toyota's red coolant.

Extreme engine overheating even while cruising in 5th on a level freeway, on a cool night. Lots of aluminum was missing inside the head. Couldn't find a replacement 22R head at the time, only 22RE heads, so the shop TIG'd more metal in to fill the holes... allegedly. Whatever, that fix didn't last. Struggled to reach 100K miles, and traded it in.

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Filter it and buffer it. The chemicals are available. 10.0 or 10.5 ph buffer. I have been using a bottle of Sodium Borate 10.0 reference buffer solution I got from a chemistry proffessor neighbor.

Or buy Prestone Command SCA

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Clare Snyder

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