Do I need to do anything special to bleed front brakes only?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Matt98svt, May 17, 2026 at 2:23 PM.

  1. Matt98svt

    Matt98svt Junior Member

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    Just picked up a 2012 prius and replaced the front pads and rotors, the rear were already done at toyota this past year. So Im only looking to bleed the front brakes. Do i need to put the car in service mode or anything special if im only bleeding the front two calipers? I know it has electronic brakes in the rear but from what I recall the front on normal so I gather I can pump the brakes with the car off and just open the bleeders to bleed them? Thanks in advance
     
  2. ChapmanF

    ChapmanF Senior Member

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    Did you open the hydraulic connections at some point of your pad-replacement job? Bleeding is only needed if you did and air could have entered.

    The system is electronically controlled front and rear. What's different about the fronts is that there are two front hydraulic circuits: the one used when the brakes are operating normally, and the one used as a fail-safe during fault conditions.

    The fail-safe circuit behaves like conventional car brakes, when the car is off. If you "pump the brakes with the car off and just open the bleeders" you're bleeding that circuit. That's not the one used in normal operation, though.

    If you're sure the only air in the system is down at the caliper ends of the lines, it can still be enough to get that air out.
     
  3. PriusCamper

    PriusCamper Senior Member

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    I'm glad we agree on not needing to bleed the brakes when changing brake pads. Suspect cars a 1/2 century ago probably weren't as reliable with hyrdalics and flushing and bleeding was part of every break pad change.
     
  4. ChapmanF

    ChapmanF Senior Member

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    I often will open the bleed screw while pushing back the piston for a pad replacement, so I am not forcing the fluid from the caliper back upstream into the high-rent parts of the brake system.

    But if I'm going to do that, I start with an upward loop of fluid-filled hose attached to the bleeder, so when I open it there will be no air going in, and only fluid coming out. Then I can just close the bleeder again, with no need—as I guess we agree—to do any brake bleeding as a follow-up.
     
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  5. Tombukt2

    Tombukt2 Senior Member

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    I do similar on these abs car
     
  6. PriusCamper

    PriusCamper Senior Member

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    I have a hard time believing that forcing the fluid back to reservoir with the 12v battery disconnected is going to be a problem? I've done both gen2 and gen3 with the simple tool to press the calipers apart with a thumb screw and it's always been an instant increase in fluid in the reservoir. It's kind of like that rule of cracking the reservoir fill cap before you push the caliper pistons back. It's a good idea, but the fluid going into the reservoir isn't goign to compress much air.

    However your method would make sense one time I did brakes and the fluid was topped off in the reservoir and the new brake pads pushed the reservoir to overflowing. But a turkey baster could solve that faster than a hose on a bleeder nipple, especially in climates that are prone to rust and corrosion.
     
  7. Tombukt2

    Tombukt2 Senior Member

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    Just crack the passenger side front bleed screw first let drip 3 min do other side front same amount. Should be