How tight should the parking break be?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Higgins909, Jun 15, 2021.

  1. Higgins909

    Higgins909 Member

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    I tightened up the parking break a year or so ago. I just don't know if I did it tight enough. I did this by tightening a nut under the dash. Was probably connected to the parking break pedal. I'm not sure if there is another way to tighten it. It will hold in neutral. If you give it a little bit of gas, the rear will dip down like, but if you give it a smidge more, the wheels will roll. The wheels will not drag.

    I was thinking it should be a little tighter. I think it will drag in the wet. But not in the dry. Thoughts?

    Thanks,
    Higgins909
     
  2. PriusCamper

    PriusCamper Senior Member

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    I wonder if there's an additional easy to access location to tighten the parking brake?

    I've gotten into so many Prius that parking brake went all the way to the floor and didn't work because it was so loose.

    But because Prius parking brake actuators are known to fail and because my 07 rolls much further then it used to when in Park, I always use the parking every time I push park.
     
  3. Higgins909

    Higgins909 Member

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    It will be something to look into myself on the weekend, when I have time. I also use the parking brake every time I park. Park has was too much roll for me. Probably a neurological problem, but I find it super disorientating. It would seem I used the wrong brake in my OP.
     
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  4. ChapmanF

    ChapmanF Senior Member

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    I haven't gotten into many Prii where the parking brake was especially loose.

    The spec is that the pedal should click 8 to 11 times when you apply it with 67.5 pounds of force. That is not a lot of force for pushing a pedal with your foot. If you overdo it, you'll get more than 8 to 11 clicks. Unless a car is being driven often by Sasquatch, adjustment of the cable won't necessarily ever be needed in the life of the car. In many cases, if the parking brake does seem loose, the true cause will be in the rear brakes (especially if they are drum style, as in Gen 1 and 2 and the top-hat parking brakes for the v). In such cases, tightening the cable only conceals the problem.

    The parking brake is only required to hold the stationary car against gravity on a reasonable grade (the motor vehicle standards I'm sure say what the grade is, but I don't remember offhand). It doesn't have to be able to prevent you driving away under power.

    The parking brake is entirely separate from the park mechanism in the transmission. The park actuators that sometimes fail in Prii are for the mechanism in the transmission and have nothing to do with the parking brake.

    The transmission park function works by forcing a metal pawl into a notch in a gear. That is a pretty positive stop. It would take some kind of really crazy wear scenario for the width of those notches to be any different in an old Prius than in one that just drove off the lot.

    [​IMG]

    (That image might be from a Subie, but it's a pretty good illustration of what the parking pawl arrangement looks like.)
     
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  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Last couple of pages in this:
     
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  6. Higgins909

    Higgins909 Member

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    How am I supposed to count the notches? I realized the other day that my parking brake pedal doesn't have to be pressed all the way down to be released. But I can't hear the notches unless I rapidly press it down... I just put it all the way down until it stops. I have no idea how much pressure I'm putting on it.
     
  7. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Maybe that step 3 on last page, checking parking lever clearance, is just as good a check? Hadn’t read through that till now, nor have I done the check myself.
     
  8. ChapmanF

    ChapmanF Senior Member

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    Yeah, they're quiet on mine too. Maybe get your ear closer to it, or use a mechanics' stethoscope, rest your finger on the pawl while pressing (don't get pinched!), or see if you can count the teeth after pressing it. Kind of a pain; most of my other vehicles made clear-as-a-bell clicks that were easy to count.

    That might be too far (and might explain needing to adjust the cable, if it's been done that way a lot.)

    For purposes of checking the adjustment, you definitely want to be somewhere in the ballpark of 67.5 pounds. This probably doesn't call for rigging up a spring scale there and being all fastidious about it. But it might be worth working out some way, maybe next time you're at a gym, to just set something up and get your leg used to what a roughly 65 or 70 pound one-leg press feels like, and try to feel about like that when you're checking the brake.

    I'm not a big guy, and I remember how surprised I was at first by what I could leg press. 65 or 70 pounds just isn't very much, so you could easily be overdoing it if you haven't cultivated some sense of what that feels like.
     
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  9. Valiant V

    Valiant V Member

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    I don't normally use the parking brake on vehicles with automatic transmissions. Never had a failure. (knocking on aluminum alloy) Even on manual transmission cars - leaving it in first or reverse gear make it dang hard to roll the car away without a parking brake set. On hills, I still remember the old driver's test front wheels turned towards/away from the curb as appropriate.

    Seems the Prius manual (2017 4th Gen, Trim three) harps on using the parking brake - so I use it once in a while - still not often.

    'Course, that means I tried to drive away with it still on the last time. I thought it was "odd" that the car didn't do it's usual "creep" forward when I took my foot off the brakes. Gave it a little "gas" and it still didn't move, but I felt the suspension torque-up a little. That tipped me off that I still had the parking brake on. (no, wasn't paying attention to the dash lights.)

    Ironically, I had really only applied it the previous drive to count the clicks because of this thread. It was within spec with my guesstimate of force applied. If anything, tighter rather than looser.

    Now that that's done, I'll likely be ignoring it again and it won't be used until the guy at the inspection station checks to make sure it works.

    Being from Chicago, I'm averse to parking brakes. Not only because the place is flat and even in neutral, your car is unlikely to ever roll away. But also because rust plays havoc with parking brake cables and applying a rusty one may mean that it won't release when you want to roll again.
     
  10. ChapmanF

    ChapmanF Senior Member

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    Pretty regular use makes for pretty good insurance even against that. And modern ones generally have cables now that are sealed with a rubber accordion boot, not like the open ones of my yoot where salt water would get all up in the cable.

    One still does hear advice to leave the brake off if a big winter storm is coming, something that might ice and freeze things in the applied position.

    And certainly if a car's going to be stored for a while, you might not want it sitting there with the brake applied the whole time.
     
  11. Valiant V

    Valiant V Member

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    All true - and those cables of your "yoot" are the ones of mine as well.

    Though regular use will likely keep the cable from seizing (until it rusts away and breaks outright), in my used-car buying days, I wasn't able to have the PO exercise the parking brake regularly. So after one or two "aw nuts!" later, I gave up on parking brakes and just relied on other means.
     
  12. PriusCamper

    PriusCamper Senior Member

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    By other means are you saying you carry rocks around and put 'em under your tires? :)

    Because if you're solely depending on a slightly less than relibale parking brake actuator, you might want to save this link for future reference: My brake actuator replacement | PriusChat
     
  13. Valiant V

    Valiant V Member

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    I haven't had to go the improvised wheel chock route yet with any of the dozen beaters I've driven in my career.

    I've found the parking mechanism in the transmission to be more than sufficient and haven't ever had a problem with one.

    When driving my cars with a stick, I'd use the parking brake if I were leaving the car for more than a few minutes. For short times, I'd stick it in reverse or 1st gear. I don't have to deal with hills, but if I did, I'd use the parking brake.

    I don't think your brake actuator link above applies - does it? That looks like something for the service brakes. Parking brake is completely mechanical. (Isn't it?!)
     
  14. PriusCamper

    PriusCamper Senior Member

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    My original point when conversation began is Prius doesn't have a regular park function in it's transmission. Instead it has a parking brake actuator which is a small locking mechanism that fails and is not so easy to replace. If you click the link in my post above you'll see links to all the priuschat conversations about this actuator.

    In my Prius, once the short roll after I put the car in park turned into a longer roll I started using my foot brake to extend my actuator's lifespan.
     
  15. Valiant V

    Valiant V Member

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    I looked at that link - again - and it doesn't seem to apply to the "park" function - but rather the hydraulic service brake actuator.

    Now, if there's something buried a couple of clicks deep in there, I may have dismissed it before I got to it, but the initial post in that thread is all about hydraulic brakes, bleeding, etc.

    If you're in a situation where your car is gonna "roll" when it's in park, then yes, by all means, use the parking brake.
     
  16. ChapmanF

    ChapmanF Senior Member

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    o_O None of that makes any sense.

    • The link given refers to people replacing the actuator for the hydraulic brakes. That is expensive and annoying to replace, but has nothing whatsoever to do with either the parking brake or the transmission Park function, both of which a Prius definitely has.
    • The park function in its transmission looks pretty much exactly like the park function in any other transmission, like the one in the photo upthread in #4.
    • The parking brake is a cable to the rear wheels and is independent of both the transmission Park function and the hydraulic brakes.

    The bog-standard Park function in the transmission changed between Gen 1 and Gen 2, only in how it gets moved in and out of position. In Gen 1, it had a lever that came outside of the transmission case and was hooked to a cable to the Gen 1 gearshift lever. Starting with Gen 2, it just gets moved in and out by an electric motor acting on it through a 61:1 reduction gear that you could probably redavinate for use as a winch.

    [​IMG]
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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  18. ChapmanF

    ChapmanF Senior Member

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    Got it in one. :)
     
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