Pulls to right light braking...straight when heavy braking??

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Dan Ger, Oct 26, 2018.

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  1. Dan Ger

    Dan Ger Junior Member

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    400,000 miles on this 2008 Prius. Shop says the only thing that makes sense is brake actuator (believe that's the same as ABS pump). Had already bled pump and brakes with no change. Calipers and brake wheel cylinders are good. I'm not totally convinced that the pump is the problem but these guys are the experts when it comes to brakes. No brake warning light or abs light. No pending codes. It's just kind of a pain to replace the pump so just want some input. Braking hard seems to brake straight(er) but braking lightly pulls right. What the heck?
     
    #1 Dan Ger, Oct 26, 2018
  2. bisco

    bisco cookie crumbler

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    i wonder if light braking is activating the right caliper first. is it a diagonal system?
     
    #2 bisco, Oct 26, 2018
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Should be in Gen 2 forum?

    Is braking effort about the same? I'm just thinking of a previous vehicle we had (disc front and drum rear): it had a brake fluid replacement at dealership, and somehow it ended up with one rear brake inactive. Subsequently braking required more effort, and just as you were coming to a stop there'd be an odd side-to-side sway.

    Just for giggles raise the rear, and have someone press the brake pedal while spin the wheels: maybe one side is not grabbing?

    And with the fronts: you're sure all the caliper pins are lubed and free?
     
    #3 Mendel Leisk, Oct 26, 2018
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  4. Dan Ger

    Dan Ger Junior Member

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    I would need to check into the possibility of it being a diagonal brake system. These cars always seem to surprise me with how unique they are. I would think the shop would have checked for sticking pins/calipers since that would be the more obvious solution. I will check the rears like you said. The fronts may be more difficult since you would also be throwing the power regeneration motor into the mix. I was wondering about the possibility of gears not meshing axle to differential or maybe axle is not all of the way inserted. Never heard of anything like that but having the high miles might contribute to the possibility. I need to take this out again and really pay attention. I seem to remember that it brakes straight when I brake hard.
     
    #4 Dan Ger, Oct 28, 2018
  5. 05PreeUs

    05PreeUs Senior Member

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    So that's the clue. Understand that the brake system does NOTHING different between a soft, moderate and hard brake, so long as there is no "abs" event (wheel skid).

    I suspect, based on the fact you can feel the pull, is that one front caliper is not sliding freely. This is a classic complaint when we find a binding caliper slide or sticking caliper piston.
     
    #5 05PreeUs, Oct 29, 2018
    Last edited: Oct 29, 2018
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