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Advice on brake booster/master cylinder replacement

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by skinnyboy, Mar 22, 2023.

  1. skinnyboy

    skinnyboy New Member

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    First off, I would like to sincerely thank everyone involved in the upkeep of this site, and especially all the folks that post such invaluable information. What a fantastic resource!

    Our 2012 V brought up ABS, ECB (!), VSC, and PCS warning lights simultaneously. Jumpered 4 and 13 on the OBD connector and brought up the following faults. (I believe the DTC's listed after are correct, but must admit I found the manual challenging to utilize).

    ABS /34 C0215/34 Rear speed sensor L.H.

    ECB /62 U0123/62 Lost comm. with yaw rate sensor module.
    /94 U0073/94 Yaw rate comm. disabled.

    PCS /31 Unsure of DTC.
    /41 Unsure of DTC.

    My assumption is that, since the three codes I believe correct all have one common failure point in the brake booster/master cylinder-skid control unit, that we are looking at a replacement, especially as it's a known issue and the warning lights came on together.

    Would appreciate any advice or thoughts regarding items we might check prior to ordering the master cylinder!

    Thanks!
     
  2. hchu1

    hchu1 Active Member

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  3. skinnyboy

    skinnyboy New Member

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    Appreciate the link, sadly it appears that our car is excluded due to the particulars of the program.
     
  4. Tim Jones

    Tim Jones Senior Member

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    What are the brake pedal symptoms?
    I know all about this as I have experienced this.
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    This video's pretty good, on the brake booster and actuator (just winging it on the names...) replacement process;

     
  6. ChapmanF

    ChapmanF Senior Member

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    There are known issues with the booster/master cylinder/ECU, but suddenly out of the blue deciding there are problems with one wheel speed sensor and the yaw rate sensor isn't really one of those known issues.

    In general I don't encourage the sort of "lights came on together and there are no coincidences" way of thinking through a problem, mainly just because in real life there are coincidences. (And also, when more than one of the ABS/VSC/brake lights come on together, it's not a coincidence anyway, for a simpler reason: those three systems often set codes that talk about each other having codes, so boom, you get more than one light.)

    If it were mine I would just start going through the troubleshooting steps for the codes being reported. If it does turn out that the ECU is the problem, that's the way the troubleshooting steps will point.
     
  7. Matt98svt

    Matt98svt Junior Member

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    I will start by saying I would get it looked at professionally before jumping to replacing anything because it could be something much simpler and cheaper (speed sensor maybe?) In fact, almost all of issues I have read about with regards to having to replace the brake booster and accumulator has first been characterized by the buzzing noise of the pump cycling on and off long before the any codes present so hopefully it is something much simpler. If it does turn out to be that, I just got done replacing my brake booster assembly as well as the brake accumulator on my 2013V with 182k. Mine started cycling on and off a number of months ago and it got more and more frequent. At the time of replacement it was about every 10 seconds it would cycle on but it never threw any codes, just sometimes made an additional hiss sound when holding the pedal at a red light maybe. I ended up replacing both the booster and actuator all though I have read it is almost always the upper unit that goes bad and leaks. I purchased both pieces from a junk yard online for $400 from a lower milage V. If you buy used you must make sure it is from a V and from a similar year (I think 2012-2014 years only would work for my 2013). And while you can get a new actuator for a regular prius for under $600, new ours for the V models is closer to $1200 for some reason!? I am fortunate to have an extra vehicle so I was able to take my time doing the work. While I had the cowl off I also changed the spark plugs and cleaned the EGR valve cooler and intake manifold, replaced the PCV valve and changed the water pump, inverter coolant and radiator coolant. Last thing I need to do now is change the front brake pads. I got started on that but the place I ordered from sent me pads for a regular prius not the V pads which are different. Anyhow, over all it is not a difficult job (but tedious) and there are some tools like ratchet wrenches etc and a few other things you really should have before starting. The real trick to replacing these parts is bleeding the system after installing everything. That took as much time as the actual install itself since I was not familiar with the steps and is different than traditional brake bleeding. I was very concerned after I installed all the parts my brake pedal would literally go to the floor. After the bleeding process though it has working perfectly and I have had no lights and the brakes work great. If I were to do it again, I could probably do it in 1/4th the time. In fact I have no clue why they charge such crazy amounts to clean the EGR or replace the plugs etc (I forget the exact amount but a local hybrid shop wanted 3k+ to do the braking work on mine) but none of it is really complicated at all. In the end I my techstream version would crap out right in the middle of the bleeding process so I ended up using a Thinkdiag plus scan obdII scan tool to do the bleeding process and it did everything it was supposed to and handled the linear valve offset etc. I hope this is some help and if you do decide to tackle the job yourself I can certainly add more detail, this is just some basics of my experience. And others have stated there are some really good videos online that were helpful to me as well as other members here that were very helpful, great community here
     
    #7 Matt98svt, Mar 23, 2023
    Last edited: Mar 23, 2023
  8. ChapmanF

    ChapmanF Senior Member

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    Just to make sure future readers see the right terminology, in a Gen 3 (and a Prius v or c), the "booster" and "actuator" are the same part (so if you replace it, you did replace both of those :)). The "booster pump" is the other, lower, part. And yes, because "booster" and "booster pump" are such similar names, it is pretty common for people to mix them up.

    [​IMG]
     
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  9. skinnyboy

    skinnyboy New Member

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    Beyond appreciative of all the constructive feedback, thanks gentlemen!

    Tim, there doesn't seem to be a noticeable change in braking performance, aside from the pump running a little more consistently than I recall. Could be simply a heightened awareness on my part. (My son has been driving it primarily for the last year.) On the short drives I've done to assess it doesn't seem to be regenerating as effectively as before.

    Mendel, awesome video. Have learned so much from Youtube, thanks.

    Chapman, great advice. My son, the computer whiz, has Techstream up and running, just waiting on the cable to further delve into the process. I saw your post in the Gen 3 forum, after starting this thread, that suggested re seating the wiring loom connector on the actuator, will try that this morning, as well as looking at the wheel speed sensor. Believe I have the correct part numbers for my 2012 V, 47050-47180 for the master cylinder/actuator (list $4151 CDN) and 47070-12020 for the pump (list $3967 CDN), if it comes to that. The naming of these parts is definitely confusing, and the prices simply outrageous in Canada. Would source from the US/Japan. Going forward, this would make me think very long and hard before buying another Toyota. I can't imagine a reason for such a huge discrepancy between Canadian and US prices other than gouging.

    Matt, thanks for the overview of your experience. Certainly removes some of my trepidation about approaching the task if it does come down to the actuator. Concern I have is with corroded brake lines after so many years with salted roads here, but it is what it is. Appreciate the advice on bleeding and the scan tool if the knock off Techstream doesn't work. No problem paying for the official version if it's necessary too, and we know we'll only need it for the day. I've done the brakes almost annually, water pump, plugs, EGR cleaning (that was fun), coolant, and trans. fluid as well. Also the parking brake cables, they were almost as much joy as the EGR.

    Best, Andy
     
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Can you elaborate as to which specific model you used; that sounds very interesting.
     
  11. skinnyboy

    skinnyboy New Member

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    It seems as if the issue was the LR wheel speed sensor. Checked the continuity last night (as was possible with the hub in place) and seemed to read open. Changed the hub today, cleared the faults, short drive and the codes haven't returned (knock on wood).

    A few thoughts for anyone facing the same issue(s).

    Not having had the speed sensor connectors off before it was a challenge. The grey strain relief/retainer/cover thing was filthy, luckily the pigtail was clean inside. Pleasantly surprised given how rusty and dirty the car is. Learned how to remove the cover from this video at 3:21:


    Trying to get the meter leads onto the terminals on the speed sensor was likely the worst part of the job. Pulled the plastic covers back on my meter leads and taped them together at what looked like the approximate width of the terminals and felt around to touch them inside the plastic housing. Like playing the game Operation but in reverse with your eyes closed. Kinda, but much worse.

    From that point the job was a breeze, as far as dealing with the ridiculous "drum in hat" parking brake ever is in the rust belt. Note: much easier assembling the parking brake with the hub out, then reinstalling the hub.

    The hub came out easily using a 1/2" x 2" all thread socket head, nut, and washer to force the hub out, by utilizing the holes in the wheel flange. Placed the base of the socket head (bolt would work too) against the heads of the backed out mounting flange bolts, turned the nut against the wheel flange in a kitty corner fashion and it slid out. Sorry I didn't get pictures but it was two degrees and raining. After shot with "special tool":
    Rear hub.jpg

    Contacted the Toyota dealer to check stock on the hub. Parts kid: "30 on back order." Me (sweating): "ETA.?" Parts kid: "Don't know and don't care." Okaaayyy then. Fortunately a fairly local aftermarket parts supply had one for $100 less than Toyota's.

    Huge thanks again for all the great advice folks! Time for a well deserved Guinness.

    Cheers, Andy
     
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