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Old 11-12-2015, 19:20   #1
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Testing Coolant Temp

I had the boatyard that has my boat test the coolant while winterizing. They said it tested +10F. I'm surprised it would test this high, as I changed it two years ago using Prestone premix 50/50 in the yellow bottle. Could 1.5 years in the tropics kill the anti-freeze property of antifreeze that completely, or is it more likely the boatyard is using a crappy hydrometer improperly? This boatyard is already way overpriced (4 hours to remove the mainsail?) and I would hate to see how much changing the antifreeze would cost. Thanks

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Old 11-12-2015, 19:53   #2
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Re: Testing Coolant Temp

I will add when I last saw the antifreeze in June is was still bright green/yellow as you would expect.

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Old 11-12-2015, 20:24   #3

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Re: Testing Coolant Temp

I did not know that the specific gravity of the coolant determined the freezing point.
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Old 11-12-2015, 20:38   #4
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Re: Testing Coolant Temp

10 degrees is way high. You may not have replaced all of the coolant when you replaced it or the coolant could have degraded over the past year and a half. Replace all the coolant with "permanent" coolant.
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Old 11-12-2015, 20:41   #5
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Re: Testing Coolant Temp

Originally Posted by Guy View Post
I did not know that the specific gravity of the coolant determined the freezing point.

I think it does, I remember anti freeze testers that had several little balls in a glass tube, the more balls that floated, the lower the freeze point. I go way more than 50%, but I'm after anti corrosion, not freeze point myself

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Old 11-12-2015, 21:42   #6
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Re: Testing Coolant Temp

(I've worked in the AF industry for many years, including one formula patent)

The simplest advise is to get a pocket refractometer, which reads EG/PG and battery SG also. The SG (ball) units have serious reliability issues and are no longer considered a good method. (freeze point correlates to both SG and index of refraction) However, you need to know which type it is (EG/PG), and color is not a sure indicator.

Freeze protection does not degrade with time, only with dilution. Corrosion protection does degrade; typically many years, but certain engine defects can ruin antifreeze within weeks.

RobinAir Coolant and Battery Refractometer ROB75240: Advance Auto Parts
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Old 12-12-2015, 02:39   #7
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Re: Testing Coolant Temp

When I installed my Beta, I was told that the specific mixture (in this case 33% to 50%) was critical to capture the heat from the engine. I wouldn't use another percentage of dilution for that reason. Also that ethylene glycol (the yellow-green stuff) was critical for the same reason, and not to use the pink stuff.

And yes, it does degrade. Beta specifies replacing the mixture at prescribed intervals.

What is "permanent antifreeze"?

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