Does Coolant or the water in it evaporate?

[75BRONCO]

So the cruiser was low on coolant the other day so I filled it with water about two weeks ago. (not distilled I know but need to get going) I checked it again today and a bit low from where I filled it, I think. I checked the oil and coolant everything looks fine. No noticeable coolant leaks, I've done the PHH. So I was wondering does coolant evaporate or ....

 

[inkpot]

Howdy! Water will evaporate much faster than coolant. But, neither one will evaporate while it is inside of a sealed up cooling system. You could have a pin hole leak anywhere in the system that can be hard to spot, or you could have a bad head gasket that is allowing a little coolant to be sucked into the cylinders and burned. I've had that happen on two different non-toyota engines. John

 

[wxm]

So the cruiser was low on coolant the other day so I filled it with water about two weeks ago. (not distilled I know but need to get going) I checked it again today and a bit low from where I filled it, I think. I checked the oil and coolant everything looks fine. No noticeable coolant leaks, I've done the PHH. So I was wondering does coolant evaporate or ....

How low was the reservoir before you refilled with water? If it was bone dry, part of your refill might have made to rest of the cooling system as needed after you effectively purged out the air. If that's the case, you might not have any leak. (think for the best). I would fill it up again, and keep an eye on it for the next couple of days. If all go well (no leak), then give it a flush and refill with proper coolant.

 

[Ebag333]

How low was the reservoir before you refilled with water? If it was bone dry, part of your refill might have made to rest of the cooling system as needed after you effectively purged out the air. If that's the case, you might not have any leak. (think for the best). I would fill it up again, and keep an eye on it for the next couple of days. If all go well (no leak), then give it a flush and refill with proper coolant.

What he said.

Also check your upper and lower radiator tanks for leaks/seepage, and your PHH.

 

[rmatzen]

Also make sure you are checking the car at the same temp, checking the coolant level hot vs. cold will give you a very different result.

 

[75BRONCO]

Thanks for the advice, sometimes you always expect the worse, but its nice to have a collective of ideas to bounce thoughts off of.

 

[landtoy80]

Will the water or coolant evaporate in the overflow bottle over time?

Mine is below the low mark on overflow bottle. I filled it some time ago (didn't make note when, did this time) and its at low mark again.
I see no leaks, new radiator last year but have drove a ton of miles so its not air in system. I dont have rear heat, removed the hoses to rear heater, no signs of leaks anywhere but haven't ruled out a pin hole leak. Water pump not leaking.

How slow can a head gasket leak? I have a head gasket test kit I got about 6 years ago. It has froze every winter so I am not sure if its still good (will ask manufacturer)

 

[e9999]

well, if nothing else it's bound to evaporate a bit in the overflow tank since that one is not perfectly sealed I imagine.

 

[etx]

Mine slowly goes down over time. Can't find leaks I just try not to think about it. AHeM am waiting on blackstone labs to send me the sample bottle to get the oil checked out just in case.....oh God nooooooooo!

Sent from my SAMSUNG-SM-G530AZ

 

[Landseer]

A 50-50 mixture of Ethylene Glycol (active ingredient in coolant) and water has a similar vapor pressure to that of straight water:

Vapor pressure is measure of how quickly a liquid evaporates, boiling corresponds to a vapor pressure of 1 atm (760 mm Hg). The engine bay can get pretty warm, lets say 60 degrees C, at this temp the vapor pressure of the coolant is just over 100 mm Hg. This could lead to a significant evaporative loss but only the coolant in the overflow bottle can vent to the atmosphere and it has to do so through a small hose. Over a period of months to years this could definitely lead to a measurable loss of coolant.