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Broad Reachin'
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I was at the boat recently prepping her for spring launch and noticed that the coolant in the overflow reservoir on our Universal M-25xpb is below the "low" line. I seem to recall it being properly between the "low" and "high" marks last fall. Have the crazy cold winter temps messed with the fluid or perhaps I have a leak somewhere? Any cause for concern?
 

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Have you taken a sample of oils and had it analyzed? If you can't find a leak external to the engine, there may be one internally. Coolant in the oil is how the internal leak will show up.

A block test would also help identify an internal leak.

The cold temps may have impacted the various seals/gaskets.
 

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bell ringer
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Both of the boats I have had have done this each year. I don't know why but it always seems to end up in the engine bilge pan. I think the coolant gets slushy and expands into the overflow and then back when it warms back up (meaning less cold) and by the end of the year you just have lost some.

And I know it wasn't going into the oil as I checked that for water with a test kit.
 

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The most likely cause of coolant loss is a slight leak somewhere. The best way to find those leaks is with a cooling system pressure tester, like this :

Amazon.com: Mityvac MV4560 Radiator/Cooling System and Pressure Test Kit: [email protected]@[email protected]@http://ecx.images-amazon.com/images/I/[email protected]@[email protected]@41DxAzRrkZL

I just tested my Land Rover with one and found 3 leaks, right away. The advantage is that you can go, say, 5 PSI over the normal opening point of the pressure cap, making those leaks obvious.
 

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Check the heat exchanger. If it is full to the cap then probably the plastic tubing is not making a good seal at the filler neck. A small leak there will empty the overflow bottle in time. A pressure test will not find this leak.
 

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Both of the boats I have had have done this each year. I don't know why but it always seems to end up in the engine bilge pan. I think the coolant gets slushy and expands into the overflow and then back when it warms back up (meaning less cold) and by the end of the year you just have lost some.

And I know it wasn't going into the oil as I checked that for water with a test kit.
Does this mean you are running a mixture with less than 50% glycol, with a freeze point of >-34F? Risking slush in an engine is dicy, because that stuff that floats is water and can freeze hard in head passages. I'd run ~ 55% EG in NH, if I was expecting -40F.

Just sayin'.
 

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bell ringer
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Does this mean you are running a mixture with less than 50% glycol, with a freeze point of >-34F? Risking slush in an engine is dicy, because that stuff that floats is water and can freeze hard in head passages. I'd run ~ 55% EG in NH, if I was expecting -40F.

Just sayin'.
I'm running the right antifreeze level.
 

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I'm running the right antifreeze level.
What is "right?" How was it measured? Is it PG or EG (EG has a lower freeze point for the same concentration)? What is the lowest temperature reached?

If it slushed something is wrong. And even slushing cannot cause general expansion; that does not happen until the burst point.

Another possibility, far more likely, is that at extremely low temperatures the fittings contracted more than the hose clamps (different material) and the hoses got loose, allowing what truckers call a "cold leak." There have been many attempts at special bands to eliminate the problem in very cold climates, but generally it's considered a minor problem since the leaks are tiny. The leaks are gone in the spring and thus, hard to find.
 

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bell ringer
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never said I knew it was slush just that it was possible theory, thanks for your concern
 
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