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Flushed My Brake Fluid Tonight

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by The Critic, Jun 24, 2012.

  1. The Critic

    The Critic Resident Critic

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    Just did a brake fluid flush tonight at 35,684 miles. Used Techstream, 3 cans of Honda DOT 3 (12oz per can) and a friend for help. This is a two-person job.

    The process was a bit nervewracking as Techstream decided to be a bit glitchy and skipped the LF caliper. I had to go through the "usual air bleed" procedure on Techstream several times but it worked out in the end. Techstream also lost communication with the car once or twice, which was a bit scary.

    Subjectively, the brakes now seem to stop the car in a more linear and subjective manner now than before; I will have F8L test drive the car to compare. I also want to say that the regen braking no longer feels as sharp or abrupt, but it could just be in my head.

    In the interest of speed, I used a vacuum bleeder to flush the fronts. However, looking back, this may not have been a smart idea since this could have introduced air into the system. The Mityvac was sucking very fast and was able to move a lot of new fluid through the caliper in a short period of time, but the hose showed a ton of bubbles so the seal may not have be perfect at the screw. I may go back and manually bleed the fronts again with Techstream, but it is not urgent.

    Overall, if the Techstream glitches had not occurred, this is not a difficult job and I do not see why many dealers shy away from it.
     
  2. F8L

    F8L Protecting Habitat & AG Lands

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    I bet it's all in your head. :p You know me though. I don't sweat the small stuff so you could tell me you removed the rear brakes entirely and I'd be like, cool. LOL
     
  3. The Critic

    The Critic Resident Critic

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    ^ Could be.

    Just a few notes for someone who may be wanting to try this:

    - The rear bleeder screws take a 10mm boxed-end wrench to loosen.
    - The front bleeder screws take a 5/16" boxed-end wrench. I would've never thought that a Toyota used SAE!
    - The brake bleeder screw caps are ridiculously overbuilt, but take your time in removing them.
    - The master cyl reservoir will only let you siphon down to the 1/3 mark. In order to remove fluid the remaining fluid, you will need to use a syringe with a thin tube attached.
    - Techstream asked me to unplug the master cyl level switch, but I could not find it at the time. This did not appear to have caused any issues, possibly because I did not allow the fluid to drop halfway between the min/max marks. For future reference, the switch is actually to the right of the reservoir.
    - On the last step, Techstream will cycle the ABS pump 6 times. Be sure to heed their warning that the fluid level must be in-between the min/max mark - as the fluid level will rise significantly.
    - Techstream advises that you manually bleed the fronts by "pumping the pedal several times, holding it down, and opening the bleed screw until fluid stops coming out." Usually I only open the bleed screw briefly when I manually bleed (and not until the fluid stops coming out), but perhaps this is different. I used a vacuum bleeder, but perhaps I should've manually bled the system since I may have let some air in.
    - The order of bleeding that Techstream advises is different than what the shop manual states for the non-Techstream method.
     
  4. Dark_matter_doesn't

    Dark_matter_doesn't Prius Tinkerer

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    I've got a vacuum bleeder and used it for the first time on my Chrysler minivan recently. Bubbles in the bleeder line during bleeding operation is normal, and it's due to air leaking past the threads on the bleeder screw. You can take the bleeder screws out and coat the threads with teflon pipe tape or silicone grease, then the bubbles will stop.

    Supposedly, the bubbles don't represent air getting back into the brake system. I ignored the bubbling and haven't had any problems with the minivan brakes.

    Also, I believe others have reported that if one disconnects the 12 V battery beforehand, the brakes can be bled in a normal fashion without upsetting the vehicle's systems and without Techstream. Can others confirm this?
     
  5. xs650

    xs650 Senior Member

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    5/16 is almost identical to 8mm. Only 0.0025 inch smaller. You probably had an 8mm hex, although everything else being equal, a 5/16 wrench feels better on an 8mm hex as long as it fits.

    Are you using the official Techstream or still using the Mangoose stuff?
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    With Techstream and all, the following keeps sounding better to me:

    Periodically just baste out as much as much as you can reach from the master cylinder, and then bring the level back to where it was, with Toyota DOT 3 fluid.
     
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  7. The Critic

    The Critic Resident Critic

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    I remember 8mm feeling a tad too loose. I need to go back an redo the fronts anyway so I will double check.

    And yes, I was using mangoose.


    iPhone ?
     
  8. The Critic

    The Critic Resident Critic

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    In conversation with several techs, it is common for vacuum bleeding to allow air back into the lines. Manual or pressure is the way to go. I am quite glad that I also own a motive pressure bleeder.

    Disconnecting the 12v will not work because the rear brakes are bled by the ABS pump.


    iPhone ?
     
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  9. maestro8

    maestro8 Nouveau Member

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    I'm a big fan of the "gravity" method. Yeah, it takes longer, but it avoids potential problems introduced with manipulation of the brake pedal past its normal operating range.

    With a bleeder valve open, you can push the piston farther into the master cylinder, to the point where crud might accumulate. You can end up knocking this crud loose and getting it stuck somewhere in the system. Even worse, you can score the piston / cylinder and create a leak.

    This might not be a problem on newer cars, but I like to err on the side of paranoia. :D
     
  10. The Critic

    The Critic Resident Critic

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    It is possible to do the fronts with gravity but not the rears.

    However it may be difficult to do gravity on the front because techstream needs to be running and the car is running off the 12v battery so the time you have is limited.


    iPhone ?
     
  11. The Critic

    The Critic Resident Critic

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    As an update, the issue with the brakes' lethargic response went away entirely before I even had a chance to rebleed the fronts. So, perhaps it was indeed small bubbles that worked themselves out (as one person speculated), or it may have been something else altogether.

    In the future, as a precaution, I would advise people to either manually bleed the front calipers after using a vacuum bleeder to quickly remove the old fluid, or to just manually bleed the fronts altogether.

    At this point, since everything works perfect again I may not go back and rebleed the fronts....or I may.
     
  12. whburling

    whburling Junior Member

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    Hello,
    I just downloaded techstream 10.30.029 enterred a password to unzip the file, but did not know what to do when the software asked me for a dealer name, id, etc....I do have a "key" for later. what do i do to enter deal info when i have none?
     
  13. Pseudonymm

    Pseudonymm New Member

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    Today I attempted to bleed the brakes of my 2010 without techstream, in invalid mode. I started with the rears, but on my first wheel I think I let out too much fluid and let the reservoir drop too low and air may have entered the system. (In my defense, it didn't look like it got anywhere near the low mark, however I had drained a full pint before refilling.) My helper says the pump is making a "frothier" sound and it is moving less fluid per second. I have 750ml of unopened fluid at my immediate disposal. It seems like something other than running the pump is needed to remove the air.

    I do have Techstream. Do I have to run the air bleeding utility listed in the ABS system? I clicked through the instructions in that utility to see where it lead, and stopped where it said it was going to depressurize the accumulator six times--the thing that supposed to put a lot of wear on the parts. Is depressurizing the accumulator the only hope of removing the air, or does techstream have any other tricks it can do? Or will continuing to feed it fresh fluid and working it through the system in invalid mode eventually get the air out?

    Edit: to answer my own question a little, I think that I should
    1) get more fluid, way more
    2) follow the instructions in the air bleeding utility in Techstream and complete it (working on each wheel in the right order).

    Thanks for holding my hand...
     
    #13 Pseudonymm, Oct 11, 2019
    Last edited: Oct 11, 2019
  14. ChapmanF

    ChapmanF Senior Member

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    I would just go ahead and use the Techstream bleed utility. There are two flavors, the regular air bleeding, and the extra thorough bleeding for after accumulator or actuator replacement. The extra thorough one is what you want if you think there might be air in the head end.

    That procedure also requires access to the bleed screw that's on the stroke simulator (on the side of the actuator), and you can't reach that before removing the wipers and cowl, so there's some prep to do.

    Will the procedure repeatedly empty and fill the accumulator, and put some wear on it? Sure ... but think how many cycles it goes through in a normal month of driving anyway. If it's the procedure you need, it's the procedure you need.

    Now what bugged me, back when I was using a flaky Mini VCI to do it, was it would announce it was about to cycle the accumulator six times, and get through five or five and a half and the VCI would flake out, and it would go back to start, and this happened about half a dozen times, so instead of putting six cycles on the thing it was more like forty. More recently I used a Tactrix dongle instead, and that time, six cycles really meant six cycles.

    Mind the charge on the 12 volt battery, or hook up a charger to it before you start, to supply it the whole time. It will take a while to get through the whole procedure, and the six drains and pumps all come at the end, and if you're not careful you'll be listening to: drain ... pump ... drain ... puump ... drain ... puuuuump ... drain ... puuuuuuuuuump, and wondering whether you'll make it to the finish.

    Reviewing some other random points in the thread:

    Re: the front brakes, you'll notice the Techstream bleed procedure hits them twice. The first time, it is like a conventional bleed by stroking the brake pedal; the second time is pump-assisted like the rears. That's because there are different fluid passages for the all-else-failed fallback braking (pure hydraulic from master cylinder to front wheels), and for the normal actuator-controlled braking of the front wheels. A roll-your-own front brake bleed procedure is likely to leave one of those sets of passages unbled.

    Re: 8mm or 5/16" for the front bleeder, the recommended torque for the bleed screw is very low, so if it feels like it's going to matter any whether the 8mm or 5/16 fits better, the thing is way too tight.

    Related to that: Toyota puts very nice rubber caps over all the bleed screws. Don't toss those. They are what keeps salt water from running down the passage in the bleed screw and rusting the threads together from the inside, and that's what keeps the bleed screws nice and easy to operate. On my previous vehicles without the thoughtful rubber plugs, the bleeders could get so nightmarish it was easier to replace calipers.
     
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  15. Mendel Leisk

    Mendel Leisk Senior Member

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    I don't know how it matters, but contrary to the @NutzAboutBolts video, the Repair Manual proscribed sequence is Front/R,ight Front/Left, Rear/Left and Rear/Right. *

    I had no problems doing the brake fluid replacement, but I was very cautious about keeping the fluid level from dropping low.

    I'll attach the Repair Manual excerpts for brake fluid replacement with/without Techstream.

    * A typical Repair Manual example, the order is VERY hard to sus out. A simple diagram would have been best, or at least a sentence like the above. Instead, the instruction is a repetetive paragraph for each corner, telling you what to do (the same each time), with the only exception being a terse/abbreviated description of what corner you're supposed to be doing.
     
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  16. Pseudonymm

    Pseudonymm New Member

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    Thanks for the help! I appear to have got it fixed now--it's braking normally, no codes. My mini vci would loose connectivity with the ecu right after starting to bleed the stroke simulator (what garbage), so I ordered a vcx nano, which worked perfectly. The bleed procedure that Techstream initiates when you tell it the actuator has been replaced is rather long with many steps, but in all it took only about half an hour. It is confusing in the manual, but the procedure is preceeded by unplugging the reservoir level sensor, then punctuated by releasing the parking brake to calibrate. I charged the 12v overnight before starting. It's now at 12.6v at 50F, so it didn't put a terrible strain on it to do the procedure once. I used a further 500ml of fluid to do it. Techstream calls for the order RR, RL, FL, FR; then FL, FR again. Is that the opposite? The upside to having done it the hard way is that now I know where the actuator is--hopefully that won't ever come in handy.
     
    #16 Pseudonymm, Oct 18, 2019
    Last edited: Oct 18, 2019
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah that's precisely opposite, to the instruction in the "without Techstream" section. No idea why that would be, hopefully not a typo. I do recall you should start with the corner furthest, and progress in order to the nearest, a generic rule-of-thumb.

    FWIW, I went through the 4 corner bleed procedure via the "without Techsctream" instruction, and it also worked out. I went through almost 2 pints (1 quart) of fluid, holding a little in reserve, in case I needed to fine tune the level after a few days (I didn't).

    It seemed to go very well too: the brake pedal was nice and solid after, no problems. I think @NutzAboutBolts video showing the front brake bleeding helped with that. He uses split screen to show pressuring the brake pedal, then a very quick open-and-close of the bleed valve. The assistant pressing the brake pedal has it drop to the floor very fast, so you want to do the front bleed in very small amounts, repeated.

    Regarding the 12 volt: I have a quick-connect wired in for my charger, it's one that can be left on indefinitely. When doing stuff like this I just leave it connected.
     
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