What is the sound of one piston slapping?
What is the sound of one piston slapping?
Illustration for article titled Are self bleeding brake systems a thing?

So I trackcrossed the Corolla on Sunday and the torque vectoring system did a nice job of heating up one corner at a time to fluid boiling temps. When I left the pedal was mushier than it was before the event, not bad, but not as firm as it was. Fast forward to today and its back to almost exactly how it was when I bought the car 1000 miles ago. The sponginess is completely gone and the pedal is back to brand new levels of firmness. Only evidence of the fact that I boiled the fluid is that there’s now about .25" more travel before you get to where the pedal firms up than there was before.


So what kind of witchcraft is going on here? There was air in the lines and the pedal was spongy when I left the event. Then you let it sit overnight and the pedal magically fixes itself. I boiled the fluid in the Mini on multiple occasions (Hawk HP+ are way too hot of a brake pad for that car) and every time the spongy pedal stuck around unchanged until you spent all day cursing as you desperately fought it to get a proper bleed out of the brakes. This one magically fixes itself overnight. Are brake systems that can evacuate air from the lines on their own a thing? Why did my pedal feel come back after letting the car sit?

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