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Gen 2 brake Caliper Noise

Discussion in 'Gen 2 Prius Main Forum' started by TheLastMojojomo, Oct 26, 2019.

  1. TheLastMojojomo

    TheLastMojojomo Active Member

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    My front passenger brake caliper has been making a loud squeak but the brakes otherwise seem to function completely normally. I made a post on reddit with a video about this already and will link that below so you can get more info. Just wondering if anyone has heard a squeak like this before. All the info you should need is here : Prius Brake Squeak

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    #1 TheLastMojojomo, Oct 26, 2019
    Last edited: Oct 26, 2019
  2. magnumrtawd

    magnumrtawd Member

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    brakes are worn down to the wear indicators.
     
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  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Do you ever do brake inspections?
     
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  4. PriusCamper

    PriusCamper Senior Member

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    Sure is a weird sound it's making... When you lubed them up did you seen any signs of abnormal wear?
     
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  5. bisco

    bisco cookie crumbler

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    maybe the brake actuator
     
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  6. TheLastMojojomo

    TheLastMojojomo Active Member

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    Not the wear indicators, the brake pads were replaced 7,000 miles ago and are still like new. Checked out the pads 2 days ago. Didn't measure the wear but there's at least 10mm of pad material on inner and outer pads.

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  7. TheLastMojojomo

    TheLastMojojomo Active Member

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    I had the caliper off Friday. Lubed some stuff up, pad wear was minimal. Didn't see anything out of the ordinary. Slide pins were fine. It sounds like metal creaking under stress to be honest. My best guess at this moment is it's the metal brake pad backing plate somehow making this squeak. It's so loud though. Either that or the caliper is somehow failing. It is an aftermarket caliper replaced 7,000 miles ago. Braking still performs completely normally except for the squeak. I did have what we will call a glitch in the brake actuator that triggered this squeaking to start occuring. I posted that in the reddit thread but will copy it below for easy access to the info.



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  8. TheLastMojojomo

    TheLastMojojomo Active Member

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    Nope both brake pads look fine.
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  9. TheLastMojojomo

    TheLastMojojomo Active Member

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    I don't think so, the brake actuator runs separately from the squeaking. You can hear it running normally in the background if you listen carefully. Or otherwise I should say, the actuator doesn't need to run to hear the squeak.

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  10. TheLastMojojomo

    TheLastMojojomo Active Member

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    Here is a post I made on the reddit thread regarding when this squeaking started to happen:

    "The squeaking only happens though when I push the brake pedal. It is not something that continuously happens and the actuator doesn't continuously run. Generally the actuator only needs to charge every 3 presses of the brake pedal or so, which is relatively normal operating parameters as far as I'm aware. No abs lights are on and the brakes seem to work perfectly fine. Also I should note the squeaking doesn't happen when I first start driving and is very muffled when braking while driving in reverse. I'm a part time mail carrier and make over 400 stops a day."

    "You may be onto something though. I had a weird issue happen on the mail route a couple months back after changing my rear brakes. I came to stop and heard what sounded like gas bubbles in the brake lines that traveled up to the front passenger brake (which is the caliper that is being filmed in the video). Suddenly the brake actuator would charge, and then charge again, continously and repeatedly, regardless of me pushing the brake pedal (primary symptom of a failing actuator). It is at this exact time the squeaking began to appear randomly at that caliper, happening for the first time at this moment. Within a minute or two of driving, whatever was happening in the brake actuator sorted itself out and has ran %100 normally ever since, only charging every 2 or 3 presses of the brake pedal but the squeaking now comes and goes. I have since bled the brake lines as well and the only line that had air in it was the rear passenger strangely enough. It had no affect whatsoever on the squeaking. I will post a more informational video in the coming days. Also I am NOT a mechanic in any capacity. Just a Diy'er. I do have access to toyota techstream (pirated copy you can get on Amazon for cheap) so I could replace the actuator. I've looked into it after this started a couple months back, but the actuator has continued to run normally since the "event". (you can hear it running in the background pretty good between 14-15 seconds after I let off the pedal for a brief second). If this squeak is the actuator as you say I will have my work cut out for me. :("


    My best guess to what is going on is maybe the metal backing plate on the brake pad is somehow making this squeak when coming in contact with the piston. Tomorrow after I'm done working, with weather permitting, I'm going to try switching the backing plates on the two pads and see if that makes a difference. Other wise I would guess somehow the caliper is damaged and making that noise, but it still functions completely normally and is basically new. Only 7,000 miles old but is an aftermarket caliper. The noise is just so strange and am posting around to see if anyone has dealt with a similar noise from experience.

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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Is 2nd gen caliper piston plastic, sim to 3rd gen? Maybe it's developed a crack?
     
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  12. TheLastMojojomo

    TheLastMojojomo Active Member

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    It is plastic I believe. I looked at it when I had the caliper off and didn't notice any obvious cracks. I'll have to look closer when I get it off again. Great suggestion!

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  13. ChapmanF

    ChapmanF Senior Member

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    Bit of terminology: all of the comments above about the "actuator" "running" are really about the "accumulator". That's the thing with a pressure chamber and a pump that "runs" from time to time to pump it up.

    The "actuator" is a box of valves that click open and closed to direct brake fluid to the wheels and back. If you could hear the "actuator" running, you'd be hearing soft clicking noises, coinciding exactly with when you use the brakes. You usually don't hear the "actuator" much at all, unless you're holding a stethoscope right on it.

    In Gen 2 they happen to be built into the same box, so if you ever need to replace either one, you buy the same part. But that's not the case in other gens, and even in Gen 2 it's still helpful to know which part of the system you're hearing, or posting about.
     
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  14. TheLastMojojomo

    TheLastMojojomo Active Member

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    Thanks! That's a useful bit of information. So in my above post I should say that the accumulator kept charging repeatedly instead of the actuator. Would you suppose that the accumulator glitch I experienced above was from one of the valves in the actuator portion of the assembly temporarily malfunctioning and becoming stuck open?

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  15. PriusCamper

    PriusCamper Senior Member

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    Ah, now I see what's going on, key words "mail route" and "after market caliper." As I'm sure you know a mail delivery car is going to be harder on the brakes at low speeds than any other type of vehicle use. Because Prius has regenerative braking the mechanical brakes which are used in sudden stops or at speeds under 6mph are not built to the industrial grade that your use requires.

    Basically if you stick with it you'll become an expert on what brand of brake calipers, pads, etc. last the longest... Just keep replacing them until you find a brand that lasts a long time and consider it an additional cost of doing mail delivery. And please keep us up to date as the years go by as to which brand of parts worked best? There's no one better to test brake durability in Prius!
     
  16. ChapmanF

    ChapmanF Senior Member

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    I don't know much about the glitch (maybe I read your post too fast), but yes, a valve in the actuator that fails to close fully is one of the usual suspects if the accumulator is short-cycling.
     
  17. TheLastMojojomo

    TheLastMojojomo Active Member

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    Alright story time.

    I damaged the orginal caliper through my own stupidity delivering in the winter. I would deliberately run my prius into snow banks near mail boxes quite frequently so I could reach the box. After one such snowbank, I started getting a grinding when I would brake. I had similar experiences to this before and just assumed a slide pin was stuck or something because I had gotten noises from the brakes in the winter that would usually go away by the end of the day. But the grinding continued. I think when shoving the prius into the snow bank, I may have damaged or dislodged the pad somehow because shortly after, the right wheel basically locked up. (thankfully at a box). I went to look at the wheel well and I saw the metal backing plate that goes on behind the inner pad lodged between the rotor and the caliper hanging down somewhat. I thought well oh if I can just get the backing plate out I'll be able to drive fine as long as the actual brake pad is still in there. So I gave it a little gas and broke it free. And continued on driving normally. The grinding had completely stopped after I dislodged the metal backing plate for the and braking was basically whisper quiet again. It was still hanging between the rotor and caliper but it was out of the way. This is where my theory fell apart. I assumed the brake pad was still in there. WRONG. There was no brake pad. It was just the plastic Piston on the bare rotor. I made it about 30 more miles and almost a 100 more stops before I saw smoke coming from my passenger wheel well. Surprisingly braking felt completely normal up to that point (damn regenerative braking). Almost immediately after that the dash lit up with all the brake warning lights and I lost pedal pressure. Limped the last few miles of the route back to the Post Office still delivering on no brakes. Thankfully only had about a dozen boxes left. Got home and jacked up the car and there was no inner brake pad. I couldn't believe it. I don't know if I somehow lost the brake pad when I hit that snow bank or shattered it or something but it was gone nowhere to be seen. I never heard it fall out or anything. When the rotor locked up from the backing plate it had to have been gone already. I looked on the ground after I broke my stuck rotor free and no evidence of a brake pad. You would have thought that I would have heard some sort of thud, pop, or clank when the brake pad somehow came out but I didn't. It just went to straight grinding after I hit the snow bank. And the grinding never really changed in its pitch until the backing plate dislodged. I suppose it could have came out at that moment but I didn't see it anywhere on the ground and again I heard no weird thud or anything like that. One would figure you would hear something like that being ejected. When checking the pads on the otherside the inner one still had 3mm or so on it. It wasn't down to the metal squealer yet and I never heard the passenger side one that became dislodged squealing either. I should have noticed that coming to a complete stop 400 times a day in complete silence sitting in the passenger seat while driving but I recall no such noise.

    Kind of crazy though. No other car besides a hybrid would have made it through the end of the route thanks to the regenerative braking taking most of the force. Priuses are perfect delivery vehicles. Gets 35-40 mpg on the mail route, has a CVT transmission so never shifts gears, has regenerative braking so you should only have to change the pads between 50,000-70,000 delivery miles, and in the event of a brake pad disaster your still good to go for another 30 miles and 100 stops. Lol

    I'm not convinced that the new caliper I installed is defective yet either it seems to function completely fine just with annoying squeaking. All the braking really doesn't stress it that much more than regular driving is say in my experience. The regenerative braking does a very good job at absorbing the forward motion of the car. The brake squeak doesn't even happen until I hit that 6 mph speed wall, usually... The squeak also began at the same moment the brake accumulator "glitch" happened when I heard what sounded like air traveling to the newly installed front passenger caliper. I'll still make it 60k+ miles on a set of brake pads even with all the stopping I do delivering the mail. It was a disaster causing me to replace the original caliper in the first place, and I'm hoping it's just something minor causing the squeak on this new caliper. Haha. I'll keep you updated on the coming days what I try. If I can't figure out the squeaking I'll probably go get a caliper from a junk yard and install that.

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    #17 TheLastMojojomo, Oct 28, 2019
    Last edited: Oct 28, 2019
  18. TheLastMojojomo

    TheLastMojojomo Active Member

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    Picture of the damaged Caliper Piston from grinding on the rotor.
    20190308_171335.jpeg

    Pictures of the metal backing plate hanging down.
    Snapchat-350424551.jpeg
    Snapchat-548331088.jpeg

    Pictures of the remaining 3 brake pads. You can see they still have adequate braking material left.
    Snapchat-2056275482.jpeg

    Posted via the PriusChat mobile app.
     
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  19. Mendel Leisk

    Mendel Leisk Senior Member

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    A clear case of Prius abuse. :D
     
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  20. TheLastMojojomo

    TheLastMojojomo Active Member

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    She sure is one strong Woman though. I hope my wife one day puts up with my crap like she does.

     

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    #20 TheLastMojojomo, Oct 28, 2019
    Last edited: Oct 28, 2019