Brake Burning Smell after steep downhill

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by HaiImBrian, Dec 23, 2018.

  1. HaiImBrian

    HaiImBrian Junior Member

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    I tend to drive mountains a lot and after my last drive, my brakes emitted a burning smell. This has happened more than once. I also feel a bit of brake fade when I'm going downhill which is not good.

    I'm definitely not hard on my brakes nor am I slamming them. Pads have plenty of life yet so I'm starting to think its the material of the OEM pads just can't handle the intensity of downhill driving. I understand regenerative braking is 80% of my stopping power so the pads shouldn't be this stressed under load. Also.. I prefer to not use "B" mode because I'd rather put stress on my pads than my engine.

    Anyone have similar experiences? Has anyone use another brand besides oem pads?
     
  2. Robertto09

    Robertto09 Junior Member

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    Its so easy. Use mode B, not the brakes. You will not have a burning smell, again

    Posted via the PriusChat mobile app.
     
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  3. bisco

    bisco cookie crumbler

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    i would take a look at the pads and rotors just to be safe.

    as for wearing the engine, your thinking of the olden days when we used to downshift and use the engine to brake in a gasser.
    in a prius, it is designed for this, and will not cause any wear
     
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  4. HaiImBrian

    HaiImBrian Junior Member

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    Would checking on the brake help? I know you should relube the pins every once in a while.

    I understand the use of "B" mode but I've driven this route with other small passenger cars (Toyota Yaris, Honda civic) and didn't experience any burning or brake fading as much as the prius. I understand the prius isn't a racing car but there is definitely an issue with my pads and was wondering if anyone had similar experiences.
     
  5. Robertto09

    Robertto09 Junior Member

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    With other cars I use compression, with Prius I use mode B

    Posted via the PriusChat mobile app.
     
  6. Pluggo

    Pluggo Active Member

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    It's not the answer you wanted to hear, but everything you describe screams for the use of B, and don't think for a minute that engine braking hurts anything. Your engine will be perfectly safe and happy, spinning with no load and plenty of motor oil splashing around inside. You will be burning little or no fuel, and if you pay attention, you'll notice the engine temperature can drop quite a bit while engine-braking. P.S., it's normal for brakes to smell when they get very hot, but you should try not to let that happen. If they develop a surface glaze, they won't stop the car properly and will need to be replaced.
     
    #6 Pluggo, Dec 23, 2018
    Last edited: Dec 23, 2018
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  7. bisco

    bisco cookie crumbler

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    i think after a burning smell, all safety systems should be checked. how many miles on her?
     
  8. royrose

    royrose Senior Member

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    I agree. Living in Colorado, I do plenty of mountain driving, rarely use "B", and have never have had a burning smell. How long and steep are the downhills where you experience this? Does it happen only when you have reached full bars or other times as well? Lubricating the pins might not solve it but seems like a worthwhile maintenance and troubleshooting step in your case.
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    As you know, the Prius relies upon regen braking to carry most of the braking load UNTIL the traction battery becomes charged to the point where all bars appear on the traction battery state of charge gauge. At that point, the friction brakes are relied upon.

    Apparently you are applying the friction brakes to the point where they are overheating and causing that burning smell.

    Instead of doing that, you should shift into B once you find that the traction battery SOC gauge shows all bars. That will help to slow down the car without causing undue strain on the brakes. The use of B is not harmful to the engine or the transaxle.

    I travel to Lake Tahoe periodically, and use this approach when descending from 7,700 ft. elevation. It works well and the Prius brakes are not stressed via this approach.
     
  10. Grit

    Grit Senior Member

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    You need slotted drilled metallic brakes, you’ll be a certified racer (y)
     
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    How long are these downhills? If it's just a half-mile at most you should be ok, bu if they are serious "mountains" I'd for sure be using B. If and when it flattens out enough during your descent switch to D, before going to the gas. When it steepens enough that you're going to the brake, switch back to B.

    Here I use B for coming down Mount Seymour, that's about it locally.
     
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  12. Raytheeagle

    Raytheeagle Senior Member

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    I see your back to the old avatar staple :).
     
  13. Jimi1976

    Jimi1976 Active Member

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    Take our Prius I to high elevations all the time (I’m in Colorado). Brake smell is so frequent, as a lot of folks don’t know what engine braking is. Prius is easy with the B mode. Our Subaru, on the other hand, I toss it in manual mode and ride 3rd gear most the way.

    As for the smell of your car - it’s fine.
    Have the brakes been acting normal since?
    If yes - it’s fine. They get hot when used heavily....which is normal
     
  14. padroo

    padroo Senior Member

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    If I were you I would get the brakes checked, it sounds like something is hanging up.
    Are you on your original brakes?
     
  15. 4est

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    Check the wheel temperature when it smells

    I would guess you have a brake unbalance. So you mostly brake with one wheel instead of 4, so that gets hotter sooner

    Be careful not to get burned
     
  16. Grit

    Grit Senior Member

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    Please explain this process, how one can notice engine temp has gone down.
     
  17. Pluggo

    Pluggo Active Member

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    I watch engine temperature using a multi-function ScanGauge plugged into the diagnostic port, but if you are running your heater while in B you can notice that heat from the air vents will become cooler after a descent that lasts for 2 or 3 minutes.
     
  18. Prodigyplace

    Prodigyplace Senior Member

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    The engine is spinning due to MG1 but not running to burn gas and produce heat but the coolant and oil are circulating through the engine removing heat.
     
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  19. sam spade 2

    sam spade 2 Senior Member

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    This is defective logic.

    Until the HV battery is fully charged, the regen drag can provide most of the braking.
    After that, letting it use the engine does NOT "stress" the engine. It turns well below the design maximum speed and uses virtually no fuel in the process.

    Have you ever seen a semi stopped on a long downhill with one of the tires ON FIRE ??
    This might happen to you if you don't re-think this.
    You are doing it entirely WRONG.

    But if you insist, a complete rebuild of the brakes would be needed: pads, calipers and vented rotors.
    After that, you might need to add some brake cooling ducts too.
     
  20. HaiImBrian

    HaiImBrian Junior Member

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    This is what I should be expecting. Even for short downhill runs, I shouldn't expecting a burning smell.

    Thank you for the clarification and explainantion of "B" mode. This actually makes me more comfortable using the mode now knowing that I wouldn't stress the engine too much. Note.. even for short downhill climbs, I get the burning smell. If there is something steeper for long periods of time, I would definately use B mode.

    I think my last downhill trip was 20 minutes with occasion braking every 2-3 minutes due to turns. On a note, I also smelled burning on anothe trip that was only 5 minutes downhill.

    Brakes have been normal since but only smells when I'm going downhill. The problem that bothers me is the brake fade, when braking stops being a bit more predictable.


    Thank you everyone for all the advice!

    I've come to a conclusion that this may not be normal behavior for my brakes so I'm going to do a complete brake overhaul which will include:

    Brake Pad Replacement (probably non oem pads, akebonos look good)
    Brake flush and bleed.
    Relube caliper pins

    I'll also start using B more more often during these downhill to prevent additional strain on my brakes.
     
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