2012 Prius Plug in: Right rear "Rotational thumping"- seat vibrates, 19Mpg, low power. Diagnosis?

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by FastEddie746, Dec 8, 2018.

  1. FastEddie746

    FastEddie746 New Member

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    Hello, our 2012 Prius Plug in had a rough winter with pot holes and a minor accident were driver backed up into bumper (Scratched) as I was driving past. It has 61,500 miles and has been dealer serviced. We noticed on backup, the "horn" noise of a sticking rotor. On inspection the rear rotors were rusted with deep groove bands. There was also a rear driver side "rotational thumping noise" that varried with car speed. The passenger seat could be seen shaking with the thump noise. Gas mpg was 19 and it felt like it had no power.

    Took it to the dealer for noise. They said the brakes are shot and need all new rear rotors, pads (thickness 4mm) front turned rotors and new pads (thickness 1mm) The multipoint inspection was "green" for the brakes at all service times and the last one 6 months ago was a state inspection no report though. I see Prius brakes not needing to be replaced for 100000 miles> I was skeptical as to why just the rear rotors would rust and not the fronts. I researched the Toyota TSB--0248-12 Uneven Brake Wear on Rear Brake Pads and asked for waranty repair and was denied being beyond the 3 year/36,000.

    Needing the car, job completed, I paid the $600 bill and left only to still hear the "Rotational Thumping" Not satisfied I did more research and found that tire belt separation could make this noise. I jacked up the rear end, spun tires and they would not spin freely unless I applied force to spin them. I did find a small 1 inch by 1/8 raised bubble on the driver tire side wall. Great back to dealer. They of course could not hear the thumping and said the tire was fine. I told them to look closer and they found the Bubble and replaced the tire for $106.

    The thumping noise is improved but still there.

    1) Any diagnostic ideas on the thumping noise.
    2) How freely should the rear wheels spin with new brakes installed?

    Thanks,
    Ed
     
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Do a tire rotation- see if the noise changes location. If it does, the problem is the wheel or tire. If not, it's in the brake or wheel bearing assembly.
     
  3. jerrymildred

    jerrymildred Senior Member

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    You might have another tire with broken belts, but not as severe as the other one. Best way I know to spot it is to get the suspect wheel off the ground, place some sort of indicator close to the tread, and watch as you spin it to see if the distance between the tread and the indicator changes. Ot the tire could just be out of balance.

    But that does not explain the 19 mpg. If there's a brake sticking, that wheel should get really hot when you drive. You'll also feel the difference if you jack it up and try to spin it as you noticed. To hurt the mileage that much, it would be pretty obvious.

    Just for perspective, when our 2005 got totaled by a texter, it had over 170,000 miles on the original brake pads and rotors.
     
  4. Raytheeagle

    Raytheeagle Senior Member

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    When I lube the pins on our 2010, I check for wheel rotation while I have the car up. I usually get a rotation or 2 after reassembly.

    Our 2010 with 193 k miles on it is still on the original pads and rotors:).

    Regen braking, driving ahead and frequent care of the brakes can make this system last a long while(y).
     
    #4 Raytheeagle, Dec 8, 2018
    Last edited: Dec 8, 2018
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  5. bisco

    bisco cookie crumbler

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    welcome!

    living in the same climate as you, i can understand the issues. salt is the enemy, and the brakes need an inspection every 5k, a complete inspection and slide pin lubrication every 30k, as stated in the maintenance guide.
    unfortunately, there is no way for us to know the condition of your brakes without pictures, and now that they are repaired, that is water under the bridge. and to be honest, that wasn't a bad price for a dealer, we have seen quotes here of well over a thousand dollars.

    a few questions:

    1) have you owned since new, or what mileage did you buy it at? i have the same car with the same miles and no issues.

    2) how are you measuring mpg's, at the pump, dividing miles by gallons pumped?

    3) how old are your tires? are you rotating them properly, and replacing when tread wear demands?
    replacing only one tire is not always a good idea.

    4) what tires are you running, and what pressures?

    5) has your car had regular required maintenance done at 5k intervals?
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    They may not need to be "replaced", but Toyota USA says to do a full inspection every 3 years or 30 K miles. Verify in your Warranty and Maintenance Booklet.

    If they've done the job right the wheels should spin fairly freely. A good push and they'll go one or two revolutions when you let go.

    The rear brakes have are tricky: the pads have a small, stubby pin on the back, and the caliper piston has a raised cross-pattern on it's face. The pistons are screwed clockwise to retract them, and should be oriented like this:

    upload_2018-12-8_7-27-30.png

    The shaded areas are the raised spokes, and the pin on the back of the brake pad HAS to be between the spokes, and firmly seated thus. If pin rides up onto a spoke, then you will get terrific/constant drag, uneven brake pad wear, rotor scoring, about 50% of the inner face of rotor rusty (from lack of contact with pad), and hot dog fingers.

    I'm just kidding, that last one...

    Anyway, the drill is: assemble the brakes with the correctly oriented piston. Then press the brake pedal multiple times, get everything WELL seated. Then test drive. Then (and only then) apply/release parking brake several times (this will attempt to rotate the piston, which the pin between spokes should prevent). Then raise the rear of the car and test spin the wheels, to verify everything is ok.

    I've attached the brake info from repair manual.
     
  7. FastEddie746

    FastEddie746 New Member

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    Something is going on with the rear wheels not spinning freely. All great ideas to try. Thanks to all who responded. I will return to dealer and have them look at the possible stuck brake pin.

    Ed
     
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  8. jerrymildred

    jerrymildred Senior Member

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    Maybe a pin. Maybe a brake piston sticking and/or misassembled. If the car that hit you hit the wheel, who knows what damage might be hidden in or behind that wheel?
     
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