How do self bleeding clutches work?

Even if the highpoint is the resovoir, how does the air get out without letting the pressure out? Does it use some kind of special float valve like this?

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  • Yes, both those variations will work.
    – Solar Mike
    Feb 22, 2019 at 7:14
  • For what it's worth - I have a motorcycle with sealed clutch and brake reservoirs, and they are self bleeding. It works because the air just floats on top of the fluid and eventually works its way into the reservoir bubble by bubble, simply because of gravity. The fluid is thin enough that bubbles generally don't get stuck, even in the small tube. Feb 22, 2019 at 23:19
  • How does the air escape the resovoir though? If it could escape wouldn't this also mean the fluid pressure escapes whenever you press the pedal meaning the brakes would not work?
    – rollsch
    Feb 25, 2019 at 0:20


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