Hot brake rotors(disks) , replaced everything, its still hot

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by ToyotaCoyotta, Jul 10, 2025 at 12:01 PM.

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  1. ToyotaCoyotta

    ToyotaCoyotta Junior Member

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    Haha, I am ordering one right now as we speak, just in case
     
    #21 ToyotaCoyotta, Jul 16, 2025 at 3:23 AM
  2. T1 Terry

    T1 Terry Active Member

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    The brake hose has an inner lining with a rubber impregnated webbing over that and a coating of rubber on the outside.
    The inner hose becomes fractured and fluid under pressure builds up behind this inner layer but retained by the rubber infused mess that strengthens the hose. This pressurised fluid will be equal with the pressure of the fluid inside the hose proper, but when that pressure is released, not all the fluid will drain back out of the space between the inner and outer hose, trapping some of the fluid under slight pressure still in the calliper.
    The normal slight amount of movement side to side of the disc between the pads, can no longer create that small gap between the disc and the pad, so you get that brake dragging feeling.

    If you watch any circuit car racing the Bathurst 1000 is a great example, you will see the driver do one press on the brake pedal, before they come into the braking zone, that is to push the pads back against the disc so when they need to stand on the brakes, they have a full pedal pressure .....

    52 yrs in the trade, you never forget the important things you learnt early on ......

    By the way, what you do to one side with the brakes, you must do to the other side, if you replaced a disc, you need to have replaced both of them, if you replaced the pads, you need to have done both sides, if you replace the hose on one side, replace the other one as well ..... they are both the same age and suffered the same treatment .... if one fails, the other one will also fail .....

    T1 Terry
     
    #22 T1 Terry, Jul 16, 2025 at 7:38 AM
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  3. ToyotaCoyotta

    ToyotaCoyotta Junior Member

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    I cant thank enough for your effort to share this information, thank you a lot.

    I have just tried to do the bleed screw test,

    Here’s how it went:
    1. my disks and wheel were really hot so i stopped at a leveled spot,
    2. I loosened the 5 bolts and then used a jack to lift the car (this might have took me 3-5 mins)
    I tried to spin the wheel and it definitely had some resistace, but nowhere enough the same kind of resistance i felt first time when i noticed the issue.

    I tried to spin the wheel back and i felt resistance, then I tried to spin the wheel front and it didnt seem to have resistance,

    I took the wheel off and then went for the bleed valve, I opened it and it didnt give any action at all, no air or strong pressure, only a few drops of brake liquid, I used a wheel wrench and placed between wheel hub bolts and tried to spin it, actually I cant really tell if there is any resistance now, spinning it both ways felt the same,

    Now im sitting and thinking whether it wasnt one of the times where the brakes was locked hard enough for me to do the test or it just loosened over the 5 mins i took before I got to the bleed valve or I needed to try and spin wheel hub before opening bleed valve for a short time.

    Even today before doing the test I stopped the car and put it in Park, which means the brakes should have been released. But when I listen closely to the front left wheel, I can hear a faint noise, like the brake pads are still slightly dragging on the disc. It’s a kind of subtle friction sound, as if the car is trying to move but the brake is still holding it back just a little. I can hear this sound even while the car is stationary in Park, as

    I guess I will try this test again to make sure when rain ends
     
    #23 ToyotaCoyotta, Jul 16, 2025 at 8:35 AM
  4. ChapmanF

    ChapmanF Senior Member

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    In my gen 3, I can reach the front and rear bleeders with the wheels/tires on and the car on the ground. That required trying a few different angles the first time and I wasn't sure I'd be able to, but I was. The fronts have the advantage that you can turn them from side to side. (I can still reach them pointed straight ahead, but turned is easier.) I can't reach the rears without lying down behind the car.

    If you can figure out a way to reach the gen 2 bleeders like that, it can save you time and effort.

    Of course you still need to raise the corner you want to try to spin. (In which case, if reaching puts you beneath the car, use a jackstand.)

    You can spin either rear wheel just lifted independently. To try spinning a front wheel, you also need the other front wheel lifted, or to be in Neutral instead of Park.
     
    #24 ChapmanF, Jul 16, 2025 at 9:05 AM
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  5. ToyotaCoyotta

    ToyotaCoyotta Junior Member

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    good advice on the steering wheel angles for better access, I can still spin the wheel when in gear just only a small amount, before the gear stops, when i tried to spin wheel first time ever, I couldnt move it at all, was dead blocked
     
    #25 ToyotaCoyotta, Jul 16, 2025 at 11:30 AM
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