Does brake fluid evaporate? I noticed my fluid levels were low

no but it is something you are supposed to change every 2 years since its alcohol based

>>13943931
No, it absorbs water over time, and becomes less effective and rusts your lines.

>>13943931
Not exactly evaporate, but in rubber brake lines, it'll vanish in time, yes. The worse off/older the lines, the faster the shit is gone. Steel lines aren't holding forever either, keep in mind.

The stuff also gets old and thus loses its properties. Regular exchange recommended.

>>13943931
You have a leak, somewhere.

>>13943931
As your brake pads wear down the pistons come further out of the calipers and the fluid in your master cylinder reservoir gets lower.

It does not evaporate.
It does however capture moisture out of the air or water solution, and loses its designed abilities as a chemical in doing so to handle pressure correctly without either losing brake pressure all together, or having just a spongey pedal.

Your fluids however shouldn't be "low".
It has to be going somewhere, as the booster is sealed, as are the lines, as are the rest of the components.

I'd check for leaks around the brake booster, and the rest of the brake system. Shouldn't take more than a few minutes once all the wheels are off.

>>13943974
but that doesnt cause spongy pedal.

>>13943984
Yes it does, the spongy feeling is from the excess pedal travel when the pads aren't contacting the rotor yet.

>>13944072
thats not physically possible.
the way the pistons work is the rubber (piston rings) bends by design, thats how it moves back slightly. rubber flexes

OP back, it wasn't spongy so much as the brakes were bottoming out. Adding some fluid made it so I can at least brake now, although I don't know how well yet. Could not find a leak for the front.

Back master cylinder has a leak, but I never use the back brakes so it could have been that way for a while. The fitting is not bottomed out, not sure if it is supposed to be, and the leak is between the fitting and the steel line. I don't know a shit about brake fittings though. Definitely letting air in, I can see bubbles come up to the reservoir when I pump it.

>>13944083
The pads have tabs that pull them away from the rotor surface, once the pads are worn down there is extra pedal travel required to make the pads contact the surface again. That's the causation behind the spongy feeling. Have you never changed pads without bleeding the brakes?

>>13944099
not all pads have the same design
the piston is what moves the pads nothing else

File: leak.png (230KB, 684x625px) Image search: [Google]

230KB, 684x625px

>>13944085
It looks like according to this diagram, I just need to make the nut tight, and then do a bleed?

>>13944113
Also, I get that the diagram is showing a wrongly seated thing, but it looks like the nut and the cylinder have a matching taper that sandwiches the line, is that right?

>>13944104
So you're saying the piston itself retracts the pad from the rotor surface? You retarded son?

>>13944085
What car?

>>13944099
No it doesn't. The pistons do not retract back to their original position. I doubt you've ever changed your brakes, and I know you've never rebuilt a caliper. The brake system does not retract the pads away from the rotor, ever. If you ever had changed your pads and rotors, you'd know you have to depress the piston all the way to allow the parts to go back together. Go, and I mean go look right now, your pads are resting against the rotor. They always are. There is never a gap between the pads and rotor once the brakes are ready for the road.

>>13944134
It's actually a motorcycle BMW oilhead (which all use similar parts), but I figured it was a general hydraulic brakes question, not a really motorcycle dbt question, the only quirk being it has separate front and rear hydraulic brake systems.

Do they make an arctic grade/below 0℉ brake fluid? I live in Alaska and when it gets down to -10 and below my clutch fluid starts to turn into actual peanut butter when I'm driving and it's quite annoying. Brakes however are almost entirely unaffected. Or is it possible I have excessive water in my fluid? Car is 1.5 years old and spent it's 1st year in Texas, so not exactly a wet and humid place.

>>13944147
>abutment clips are being used on some new vehicles that help to push the pads back from the rotor to reduce drag and allow for less wear on the pads and rotors. Failing to renew these components as part of a brake job could reduce the life of the brake job and increase comebacks.

http://www.knowyourparts.com/technical-articles/7-brake-parts-neglected/#sthash.YOwwH5Yc.dpuf

>>13944125
>>13944113
Well fuck, looks line my brake line may be fucked up. I torqued the nut until it was snug and it still seems to leak.

>>13944206

Replace it. Where is the leak again and how long is the line?

And for the love of god dont use Teflon or some kind of thread sealer.

>>13944279
It's leaking between the fitting nut and the line itself, where the line connects to the cylinder. I can't actually see what it causing the leak without disassembling things, but the seal at the fitting is not working.

>>13944099
>The pads have tabs that pull them away from the rotor surface
I've never seen that and I'm not a noob.

>>13944147
correct

>>13944162
Flush the clutch fluid