I have a 2005 Toyota Corolla and I don't know why the antifreeze is evaporating. I don't have a leak, but my antifreeze is evaporating. What causes that.
Every month I have to add antifreeze to my radiator.

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    Welcome to Motor Vehicle Maintenance & Repair! More than likely there's a leak which is dumping into the system. Check your oil to ensure it's still ... well ... oil ... and not chocolate milk. Also, smell the exhaust ... if it smells sweet, it's leaking into the combustion chamber. – Pᴀᴜʟsᴛᴇʀ2 Sep 9 '19 at 20:45
  • Thank you, I will take your advice and check these two possibilities. – Renate Hinsepp Sep 9 '19 at 20:47
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    If something were to actually vaporize out of your cooling system , it would be water. Ethylene glycol boils at a higher temperature than water ( 387 F).. Loosing water would raise the freezing temperature , which can be a problem ( at possibly - 10 F ). – blacksmith37 Sep 9 '19 at 21:08
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    As Paulster said (without actually saying it), you might have a blown head gasket. – the_storyteller Sep 9 '19 at 21:16
  • You absolutely DO have a leak. Antifreeze doesn't evaporate, but the water does. BUT only if it is exposed to atmosphere (leak). It may not end up as a puddle on the ground; it may be leaving through the exhaust. But it's still a leak. Compression test and look for bubbles in the radiator neck while running. – SteveRacer Sep 10 '19 at 8:57

One of the hoses could have a small pin hole and be causing the loss over time - as the coolant only escapes when fully hot and under pressure then the coolant evaporates and leaves no trace.

The coolant can spray out into the engine compartment and not condense on any component or leave any trace around the hole... I found one by driving it hard when up to temperature and stopping and opening the bonnet (hood)... Then the fine jet was finally visible...

Seen this before and can take some finding.

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  • I would expect to see telltale marks at the source of the pinhole leak. – Harper - Reinstate Monica Sep 10 '19 at 22:16
  • @Harper well, you weren’t the one looking and I found the real leaks.... What “you” expect and what actually happened are two different things - you* should have been there - might have saved us SO much time. – Solar Mike Sep 11 '19 at 1:41

in my opinion this may indicate that your head gasket is leaking coolant to a cylindr or oil! I would recommend getting a cylinder leakage test on your car. an expensive job so good luck and NO ! COOLANT DOES NOT EVAPORATE !

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