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Hum while accelerating

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Kelli Ann, May 1, 2016.

  1. Kelli Ann

    Kelli Ann Junior Member

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    Hi All,
    I've recently purchased a used 2008 Prius with 77000 miles. I was a bit apprehensive but have started to fall in love with this car. After running some errands yesterday, I heard a strange buzzz, coming from the middle of the engine compartment. When I'm in the car is sounds like it is front of me, but seems to be more in the middle when you pop the hood. And when I'm accelerating, there is now a strong hum almost like a reving sound and it increases the faster I go. I am also getting the Maint Reqd light flashing as I turn on the car, but it goes away when the ICE kicks in, just started this in the past week. I have put about 500 miles on it since I bought it and I did buy an extended warranty.

    I am getting between 41-44 mpg, depending on traffic conditions, around town, so the MPG, so far has not been effected.

    Of course the dealer where I bought it usually has some later Sat, early Sunday service hours, but not this weekend.

    Any thoughts?
     
    #1 Kelli Ann, May 1, 2016
    Last edited: May 1, 2016
  2. Kenny94945

    Kenny94945 Active Member

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    I usually pray to the Lord above when accelerating in a Prius as opposed to humming.
    Joking aside...
    Reads like you have mechanical skills.

    I can offer these comments to maybe get you through till a dealer and warranty visit:
    1) Service engine light or maintenance due light.
    Maintenance could be that the counter was never reset.
    Service...buy tools a OBDII reader...what if any codes are stored?
    2) Try putting the car in neutral and listen under the hood while a helper rev the ICE.
    3) A stethoscope tool could also help
    4) With engine, since it increases with speed look for rotating parts, like belt pulleys.
    5) Wheel bearing could also be suspect...jack up the car and spin the wheel.
    6) Other noises (electrical, vacuum leak, coolant pressure leaks) just use your skills.
    Good luck.


    30
     
    #2 Kenny94945, May 1, 2016
  3. bisco

    bisco cookie crumbler

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    prius makes a lot of odd noises, but if you're sure this is more recent after having driven it awhile, it's worth having them take a look. not much goes wrong at 77k, typically. all the best!(y)
     
    #3 bisco, May 1, 2016
  4. magnumrtawd

    magnumrtawd Member

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    Sounds like normal Prius sounds to me. If you didn't have a Prius before 500 mi. is a short time to get used to the various sounds of a Prius. Good luck and enjoy.
     
    #4 magnumrtawd, May 2, 2016
  5. Kelli Ann

    Kelli Ann Junior Member

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    Thank you All! As these are new sounds, I now have an appt for tomorrow for Toyota to listen to it. Seems to be running hot too. So will have them check it and see if codes come up for the Maint Reqd lite too.

    Thank you again and I'm proud to be a Prius owner.

    PS: I so appreciate the PriusChat site.
     
    #5 Kelli Ann, May 2, 2016
  6. andrewclaus

    andrewclaus Active Member

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    Look in the owners manual about resetting the Maint light. It will flash on startup for a number of miles, then turn on steady and stay on until it's reset. It does that every 5000 miles as a reminder to change oil. There won't be any codes about that.

    If you detect engine or transaxle heat, something may be wrong and it's a good idea to get it checked out. The Prius normally runs cool. But there are plenty of heat sensors and if something were to get abnormally hot, you'd get a light.

    By the way, there is a normal buzz sound on every cold start and every time you shut it down, but both of those are only while the engine is off and the car's in park. A loud hum while driving is not normal, nor is excess heat.
     
    #6 andrewclaus, May 2, 2016
  7. bisco

    bisco cookie crumbler

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    can you describe 'seems to be running hot'? there is no temp gauge, so i'm just wondering what symptoms lead you to that thought, thanks.
     
    #7 bisco, May 2, 2016
  8. Kelli Ann

    Kelli Ann Junior Member

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    Re "running hot":
    I did a bit of running around, but I didn't even have 30 minutes of constant driving. When I popped the hood everything was very hot, including the Hybrid Synergy Drive cover. I was able to see there was no coolant in the radiator reservoir so it now has a nice level between low and high, as I filled it while the engine was cold (this morning). All other fluids seem to be ok.

    RE: Maint Reqd Light
    I'm hoping Toyota will check to see if there are any codes as I don't have a reader otherwise, I see all the helpful hints to reset the light. According to my Oil Change tag, I don't need an oil change until Aug or 86K miles. They tell me every 10,000 miles - is this right??? I don't put more than 8-9000 miles on a car a year, so Toyota told me at least once a year unless I take a LONG drive.

    The sound is still there and it sounds like it wants to change gears, but it doesn't, it just gets to be a louder humm. Reminds me of hearing an small airplane just going along with me. It feels heavy to drive, since Saturday anyway.

    We have an appt at 11:30 tomorrow, so trying not drive it too much until i get it looked at.
     
    #8 Kelli Ann, May 2, 2016
    Last edited: May 2, 2016
  9. bisco

    bisco cookie crumbler

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    10k is correct. i change mine every spring, also do 9-10k a year.

    what's your outside temp?
     
    #9 bisco, May 2, 2016
  10. Kelli Ann

    Kelli Ann Junior Member

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    West Central Florida - we have been 90 daily, 69/70 at night. No rain in over 10 days here, but we are due for changes Tues/Wed (rain and cooler temps).

    I have a few errands tonight, but will be taking it at slower speeds. Getting to Toyota tomorrow, I have to go on a bypass which runs 55 - 70 mph about a 30 min ride. I don't think I want to take it that fast. Something is telling me transaxle system, but I don't know.
     
    #10 Kelli Ann, May 2, 2016
  11. bisco

    bisco cookie crumbler

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    i can't argue with andrew, but i would think it would get pretty toasty under the hood. hopefully, you're just projecting and nothing's wrong. you will usually get a light on the dash.
     
    #11 bisco, May 2, 2016
  12. Kelli Ann

    Kelli Ann Junior Member

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    Thank you guys, for your continued thoughts. It's truly appreciated.
     
    #12 Kelli Ann, May 2, 2016
    Last edited: May 2, 2016
  13. goldfinger

    goldfinger Active Member

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    You might be hearing the PWM carrier frequency of the inverter. If it increases with both acceleration and braking (regen) that's probably what it is. Don't worry, at age 52 it won't bother you much longer.
     
    #13 goldfinger, May 2, 2016
  14. bisco

    bisco cookie crumbler

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    but if you hear it with the car in park and looking under the hood...
     
    #14 bisco, May 2, 2016
  15. edthefox5

    edthefox5 Senior Member

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    Is this a CPO car?

    If the radiator reservoir was empty its a good bet you may have a leak. if you do have a leak then that overflow reservoir does not reflect the true level of coolant in the rad. The rad could be near empty. The engine may be overheating. You'll never know as there is no temp gauge.

    Take off the black plastic top radiator cover so you can remove the cap on the radiator and check the coolant level when the engine is cool.

    Since you just bought it used it is wise to go to Toyota's online site and see what issues the car has seen over the years. It will show you every visit the car has seen at an authorized toyota dealer.

    Go to toyota.com/owners and join and list the car's vin.
     
    #15 edthefox5, May 3, 2016
  16. Kelli Ann

    Kelli Ann Junior Member

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    Was at Toyota dealer for 6 hrs yesterday, mostly fighting with the Warranty contractor to cover the work. It was the passenger side wheel bearing, and it had even welded it's self to the housing, this took them almost 2 hrs to remove it carefully so I didn't have to pay for the entire housing. They couldn't explain the radiator reservoir as all the hoses looked good and were clear (no clogs), fans working and pressure good. I will continue to watch.

    The blinking Maint Reqd light was reset and as all of you have stated, it goes off to help with Oil change reminders. I also found out they did a standard oil change prior to putting this vehicle out for resale, so I am to do 5000 mile oil changes , unless I change to the synthetic changes. As miles go up, this is something to think about. Salesman said 10,000 go figure.

    Thank you again for all of your feedback as I continue to learn about this vehicle.
     
    #16 Kelli Ann, May 4, 2016
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