Posted by Sherman in Idaho [108.162.246.24] on Monday, October 03, 2016 at 03:18:14 :
Thought I'd pass along an interesting observation. I have one of those little antifreeze testers with the floating colored balls. The more balls float, the lower the freezing point. I always use a 50/50 glycol mix. Filled up the cooling system of a truck I'd been working on and checked the coolant with the tester. Only one ball floated, corresponding to a freezing point of +20 deg F and about a 15% mix. Thought I'd made it too weak somehow and would have to drain half of it out and add more glycol. Then I tested another truck that had been through last winter with no problems. Only one ball floated. Next I tested the 50/50 mix I keep in a jug for topping off. Same results.
This was pretty strange, so I dug out a laboratory hydrometer and graduated cylinder and measured the coolant the proper way. I got a specific gravity of 1.68 for the mix in the jug and 1.62 for the mix in the truck. This corresponds very closely to the theoretical value for a 50/50 mix.
At this point, all I know is the floating-ball tester, which once would float several balls, is no longer accurate or useful. I don't know how the balls could get heavier over time, but that seems to be what happened, unless it was never any good and I can't remember. In any case, if you use a floating-ball tester, I advise checking it with some known fresh 50/50 antifreeze solution from time to time to make sure it's still working. Meanwhile, now that I've dug out the necessary lab equipment, I think I'll do it the very accurate way for now.
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