I was just wondering, whenever I visit any site it says pump the brake pedal three times then keep pressing it, what is the actual benefit of pumping it? And why not just press down the brake pedal and then open the bleeder screw without pumping?

  • I never "pump" it. but then now I use a vacuum bleeder too.
    – Zero
    Jun 18 '16 at 19:39
  • @Zero if we aren't using a vacuum bleeder, why do they pump it? Jun 18 '16 at 19:41
  • maybe just to kinda exercise it and move things around to get it going easier? not sure
    – Zero
    Jun 18 '16 at 19:42

You need to have positive pressure in the brake lines to get rid of any air; the pumping ensures you've built up enough pressure. And if the other sites you've read didn't mention it, you repeat the process (pump, hold, loosen bleeder valve while maintaining pressure on the pedal, close bleeder valve) until a solid stream of brake fluid comes out; that is the sign all the air is gone. And you can definitely tell the difference by the sound of the fluid coming out.

  • if you just press the brake pedal till its end, won't that make enough pressure? Jun 19 '16 at 15:41
  • 1
    Nope. I've seen fellow auto-shop classmates try it, and no substitute for pumping. Sure there is some reason, but I know it works best. Jun 19 '16 at 19:56

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