Can brake fluid "evaporate" in the brake system?

the consistency of the brake fluid will not evaporate. quite sure you have a leak at any of your wheels and the fluid leaked out. therefore you lost your brake pressure. look around your tires and most likely you will find a puddle or a weep leaking down from a hose,caliper or wheel cylinder. later!

Brakes wont get spongy from just low fluid in the reservoir. If it gets really low its possible to get spongy but it does not sound like yours were that low. What is more likely is that you have a leak somewhere and besides leaking fluid its also letting air into the system which is what is making the pedal soft. Get it towed somewhere to get it fixed, unless you know exactly what the problem is its not worth the risk that they will quit completely. Also get it fixed as soon as possible. The longer there is air in the system the more damage it will do and the more stuff will have to be replaced when you decide to fix it.

If you have a leak, which it sounds like you do, it's a serious problem. For one, pressing the brake pedal causes the brake booster to assist you in pressurizing the brake lines using vacuum from the engine's intake manifold. With the extreme pressures running through the lines, a leak will cause your fluid to leak rapidly when you press the pedal, and it will also prevent the brakes from working when you do press the pedal for the first time, due to the fact that no pressure can build.

Look for the leak, it's most likely behind one of your wheels, where there is a rubber hose. The metal brake lines generally don't leak unless they get rusted through, and that generally is not the case.

Its a leak, brake fluid does not just "evaporate". But as the pads wear, the calipers extend more and the brake fluid needs to be topped off occasionally. The reverse is also true, before doing a brake job, you need to take out some brake fluid before clampling the calipers, otherwise it will overflow.

Brake fluid does not evaporate, period end of sentence, and anyone that thinks they need to top of there reservoir because its low is an idiot, if its low you need brake pads/shoes or have a leak, in which case need to have a professional technician/mechanic address the problem.

Brake fluid doesn't evaporate. You definitely have a leak that you need to find and fix and then bleed the brakes after you replace the missing fluid.

As your brake pads slowly wear, the callipers require a bit of fluid to compensate for the wear. Fill up the master cylinder and all should be good. Check things under the hood a little more often.

Its a evil leak! But The leak should leave some evidence of residue where the leak is. I am glad your ok and no accidents happened! See how fast it leaks out when you add brake fluid! The smaller the hole the trickier to find!

Brake fluid is essentially oil and oil doesn't evaporate. You're SOL, you have a leak.