2012 Prius - New Calipers, Pads Still Dragging (hot brake discs)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by andreimontreal, Nov 17, 2019.

  1. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Brake bleed without Techstream is possible, attached is the Repair Manual instruction for this. Also watched @NutzAboutBolts video pinned in 3rd gen maintenance forum. I've done this just with tubing and bleed bolt coupIer, draining into a large jar, with an assistant pushing the brake pedal.

    I think this method is fine as long as you don't have a seriously drained system, say air in the accumulator gizmos.
     
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  2. Siward

    Siward Member

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    I had some mpg loss when I replaced my brakes due to disconnecting the battery. I went from 4.5litres/100km to 6.5litres/100km for a few days due to the ECU re-learning the optimum fuel mixture. You have had this problem for greater than one week now, so I guess it is unlikely to account for your problem. In addition, it very cold/snowing these days (which is another factor).
     
  3. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    That might be urban lore?

    I have noticed odd behavior after a battery disconnect (for brake work), specifically: for the two, maybe three start ups, the car would do an unusual rev-up, for maybe 10 seconds. But I didn't notice a mpg change.
     
  4. andreimontreal

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    Well Mendel, that's exactly what happened. My dad left the broken caliper detached, I pressed the brake pedal at some point and I lost brake fluid. We had to do tons of pumping to take air out and I'm sure we went over 100 seconds.

    As far as I understand all I need is a cable, a laptop (I got a good one), and Techstream software? I don't need to buy some third party hand held digital scanner like I see in vids right?

    I was looking at this guy mentioning keys in the pocket as an issue (I had them - and I heard the compressor prep the brakes too). That's one thing - the other not using the computer bit: I had a tinyyy hunch that the electronically controlled system had a thing to do with this. The brake disc was loose and fine and as soon as I began playing with bleeding the whole thing jammed; and I had to pump a while because of the mistake that we made. I distinctively remember this because I was on the rear right brake and that's the one that heats up the most too.

    Can you recommend the "official" way to bleed and to confirm what is actually needed for that?

    EDIT: just saw your mpg comments. Guys my MPG is doing 8-13L in urban, and the best I get is 5.5L - usually 6.5L - in highway. It's insane. Before I replaced anything I consistently got 5-5.5L most likely due to the bad pins in the rear.
     
  5. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Both ways are official, shown in the Repair Manual. Anyway, here's the method with Techstream (attached).

    Also, the golden rule of DIY Prius brake work, is disconnect the neg 12 volt cable, for the duration. I would add too: especially if you've pushed back pistons, pump the brake pedal multiple times before reconnect, so the car doesn't throw a code due to excess pedal travel.
     
  6. andreimontreal

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    Ok! Thanks! :)

    I definitely ignored the 12V cable - I was in gas car mentality like a cluts. Can you please re-explain what you added at the end? You mean just stepping heavily on the pedal several times after the job is done before reconnecting the 12V line? Also couldn't Techstream deal with those codes? This is new territory for me.

    That mechanic in the computer video, what is that line that he's disconnecting?

    So do you understand what might have happened with my brakes? This is what I understand: due to electronic control somehow I increased the default pressure applied to my calipers. Right, wrong?

    EDIT: in Techstream method they say dump DTCs (that's codes as far as I understand) would I still need to do the pedal pumping?

    EDIT2: I found some download links for Techstream? Is this free software? Also, where can I buy a reliable cable?
     
    #46 andreimontreal, Dec 10, 2019
    Last edited: Dec 10, 2019
  7. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Yes, you want to avoid the car detecting extra pedal travel, which can occur if you've been changing pads for example, and pushed the pistons back. A few pushes of the pedal before reconnecting the 12 volt to take up that excess travel, and then the car is none the wiser. It doesn't have to be crazy hard, just a few pushes till the pedal firms up.

    I think you could dismiss the codes with techstream, maybe even a few starts and the car will turn off the light itself (but store the code?). I just figure don't give it cause for concern to begin with.

    If you have the battery connected and open the drivers door, there's a very good chance the system will try to pressurize. If that happens with a caliper off it can spit out the piston.
     
  8. andreimontreal

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    Precisely what happened. I also pressed the brake to run the engine so I'm not sure if it was just the battery+key or the brake push that got my cylinder over, but, it pushed it out and I had a big spill.

    So now what, the default pressure in the line is off calibration? I get slightly more pressure on the cylinders or what happens if you bleed badly like I did? I must have exceeded 100 seconds (edit: I did NOT enter Invalid Mode - this might be the reason???) for sure as I pumped a lot of fluid to eliminate bubbles.

    EDIT: I found a short clip on the bleeding procedure without Techstream - like the one posted above by Mendel ....

    SO big question, I did not bleed like that at all. Now, how do I fix that??? Is it as simple as entering that mode and bleeding again?

    Also, is that 100 seconds continuously or in total when doing the procedure without Techstream? I assumed it's in total. Does this mean that you have to time the length of the pedal pressing and shut off Invalid Mode before 100 seconds, get out and come back in if you want to bleed some more?. And if the DTCs is stored, how is that an issue? Is it because the average person can't clear the codes or what?

    The guy in the short clip says the rear brakes are controlled electronically so that might explain why both my rears are dragging.
     
    #48 andreimontreal, Dec 10, 2019
    Last edited: Dec 10, 2019
  9. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I can relay my brake maintenance experience, and upload Repair Manual info, but for major issues, like wholesale air in the system, @ChapmanF and others better bets. (y)
     
  10. ChapmanF

    ChapmanF Senior Member

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    It's not that much, more like a third of a mm (Toyota doesn't publish their spec that I can find, but 0.3 mm is about what I got on a Gen 1 front caliper that was working right. I'd expect the rear to be comparable but I haven't measured one).

    It's a small enough amount it's not that easy to check without a dial indicator.

    [​IMG]

    Also, you definitely can't check it by somebody sitting in the car mashing the brake pedal. The reason is the brake system is so powerful that you will see a much larger reading, because you are measuring the actual stretching steel of the caliper under the braking forces. That swamps the much smaller piston retraction effect.

    A successful test is where you apply just enough pressure (e.g. from an air blowgun lightly into the caliper) so the piston just slides out and lightly kisses your spacer blocks, then release the air and note how far it retracts.

    For an on-car test rather than on the bench, you can stick a short length of hose upward from the bleeder, open the bleeder and let a little fluid escape to fill the hose, then puff from a blowgun into the free end of the hose. Play the cards right and there's enough fluid in the hose you don't inject any air into the caliper.

    I don't know that I have much more to offer specific to this situation. I can say that it isn't a matter of any 'calibration' being off for the brake line fluid pressure when you're not braking. When you're not braking, the line pressure is supposed to be zilch. (Edit: gauge, of course, not absolute.)

    The possible air in the system could be the wild card. If there's a bubble trapped in a line, it acts like a spring. It shouldn't really be easy to trap a bubble in a line under pressure, because when you release the brakes the bubble usually just expands and shoots extra fluid back out to the reservoir. In the old days you could tell a brake system needed bleeding by watching in the reservoir for little geysers when the pedal was released.

    But there's enough machinery inside the actuator that maybe, with enough air trapped there, the effects could get weirder.
     
    #50 ChapmanF, Dec 10, 2019
    Last edited: Dec 10, 2019
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  11. 2012 Prius v wagon 3

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    Some quick general comments, based on non-Prius-specific knowledge of brake systems:

    In addition to the caliper seal shear stress being the main thing retracting the calipers (as shown in the previous graphic posted by ChampanF), brakes are often designed with spring clips to keep the pads retracted against the piston(s). Are those in place? If your brake pads have little holes in them, pointing radially outward, that's where the springs would stick into. Empty holes might mean they are missing.

    Good on using the silicone-based grease. I use the following on brake systems, which is also good:

    (Permatex 24125 Ceramic Extreme Brake Parts Lubricant, in case the Amazon link does not show up)

    On the stuck slide pins, I believe a common cause of that is using grease that is not compatible with the rubber bushings on those slide pins. The grease causes the rubber to permanently swell, and even cleaning and changing out with good silicone or other rubber-compatible grease will not cause them to un-swell. Chinese manufacturing is legendary for doing things like this, so it is something you need to consider as a possibility. So you'd need to get new rubber slide pin bushings. I'd get them straight from Toyota, unless the Raybestos calipers are not an exact clone, and have different slide pins + bushings. And definitely keep track of top / bottom / etc. Before installing pads, make sure the caliper slide pins move freely. No need to proceed if they don't.

    Important of course to get the air out of the lines, but the test you did to loosen the bleed screws, relieving any residual pressure at the caliper, should remove that as a cause of the main dragging problem you're facing.
     
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  12. ChapmanF

    ChapmanF Senior Member

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    This seems like the right place to mention that if you do choose to get the parts from Toyota and stick with their "rubber" formulation, there's a case to be made for also sticking with their specified grease (all together now, RUBBER GREASE 08887-01206, the red stuff), which is a lithium-thickened glycol, not a silicone. (No need to buy a whole tube of the stuff if you buy a Toyota rubber kit, because there'll be a little packet of it in there.)

    If using rubber parts from somewhere else, then it could be more of an open question which grease choices will be most likely compatible.
     
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  13. andreimontreal

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    I actually have a dial indicator lying around. I doubt I'll even use it - the spin says it all.

    Wagon 3 yes the spring clips are in place. They don't do much in this case - the forces involved are greater.

    Agreed. My next purchase is Toyota rubber bushings.

    The bottom line so far is that I'll lift it and try the "no computer" official bleeding procedure (as I should have in the first place) and see if something changes. Got ideas? I'm all ears. I'll be back.
     
  14. dig4dirt

    dig4dirt MoonGlow

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    I am not sure about the DTC or anything, I am not fully sure how you bled and such.
    Hopefully any air in system or any codes can be cleared and such and the issue will resolve.

    The only thing I can add is my experience.
    I did my Gen3 without techstream, and by putting car in invalid mode.
    I had my misses sit in drivers seat.
    I started on the first wheel and bled out lots, to try to get reservoir down low until I added new.
    HOWEVER, I then got air bubbles. holy snit I thought. we stopped the bleeding and I added
    up the max line...like almost two bottles (12oz)
    From there I thought welp i gotta finish this and find out Wth I just did.
    Bled out until new came thru and no air. I think about 12oz worth.
    Did all 3 other wheels and then came back to the first one.
    I re-bled that one for the remaining brake fluid I had left. I dont recall seeing anymore bubbles that second time.

    I finished up and all seems fine.
    Its been 4 months and 2000 miles. all good.
    I do frequently check the temp of discs after parking and they have no abnormal heat to them.

    the 100 second time, is for each press of the brake, as far as I know.
    So obviously it is a super crazy safety thing, and I am not sure how it could ever be pressed that long.
    It only takes what maybe 5 seconds or so? let go and press again etc.
    I spent about 30 mins in invalid mode when doing mine, although if I didnt hit air it prob would have been 10min
    I was scared at the time lol.

    I watched a few vids but I had to do both my "c" and Gen3 so I spent lots of research.
    @Mendel Leisk w/o techstream paperwork was really the guide to use. much thanks.

    Lets hope you can rinse and repeat with using the w/o techstream and get this puppy back in the race!
     
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  15. dig4dirt

    dig4dirt MoonGlow

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    Just a thought?

    Did we ever measure the pad or rotor thickness to make sure they are correct and not too thick?
     
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  16. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I used a largish hypodermic needle (sans needle) with a tube extension and skinny spiggot, to do the initial reservoir empty. Easier to control. And didn't go too low. Before even starting make sure you're in invalid mode, too.

    If you've got a smart charger, maybe good to have it hooked up and charging, for the protracted time in "ready". That's what I do anyway.

    The Repair Manual order is different than the video, I stuck with RM order: start with front/right, then go around counter-clockwise (looking from above).
     
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  17. dig4dirt

    dig4dirt MoonGlow

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    I did my "c" first and it used more than I thought in fluid, so I wanted to be safe and have enough "fresh" in the
    Gen3 system.
    But the Gen3 is different then the "c" so it pushed out a ton in the 5 seconds or so on the first few presses.
    I think that is the front, which is diff then the rear? anywho I messed up but no issue.
    Lets hope we can say the same real soon with andrei :unsure:

    When researching I heard from all the back chatter that if air gets into the system,
    that it would mean "big problems in little china" type deal.

    Yes front passenger, then front drivers side etc.
     
  18. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Fronts are conventional, and finicky. @NutzAboutBolts video is priceless in showing how to bleed the fronts, with the split screen. If you've got a helper pushing the brake pedal, it seems like once you've cracked the bleed bolt open you can't close it too fast. As soon as you crack it open, the brake pedal drops fast.

    I asked my wife (aka helper), and she confirmed, the pedal was pretty much to the floor every time I cracked the bleed bolt, no matter how fast I did it.

    So do that 10~12 times per front corner, then on the rears doing some more significant (and unrushed) draining. I used two pints, and try make so each corner contributes roughly equal, albeit more on the rears than the front.
     
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  19. andreimontreal

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    Thanks guys for sharing! Dig4dirt thanks for clearing the 100 second thing, your story come smack before doing the rears just now (y)(y)(y)

    No I did not. For the rotor I guess I could compare against the old one - assuming the edges are still the same thickness, but for the pads what do I compare them with?

    EDIT: How do I find somebody else's video post? I looked into @NutzAboutBolts' account link, no shortcut to media there ...
     
  20. dig4dirt

    dig4dirt MoonGlow

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    Nutzaboutbolts vids

    Looks like #18 brake flush

    mendel has the arsenal of data for that pad thickness. I think around 12-13mm?
     
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