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Intermittent Rattling noise at highway speed

Discussion in 'Gen 3 Prius Main Forum' started by scorpion1, Sep 15, 2018.

  1. scorpion1

    scorpion1 Junior Member

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    Location:
    Ontario. canada
    Vehicle:
    2010 Prius
    Model:
    ----Canada----
    Bought used 2010 Prius August 2017 with 109 k kilometers, after about a year ,while driving at highway speed I hear some Rattling from underneath ,it comes and go away with change of speed , only on highway speed , when it rattles, if I slightly lower the speed , Rattling goes away.i have tried with and without the cruise control , only way it goes away is if I slightly lower the speed.
    To me it seems to be coming from transmission.
    I have done transmission fluid change with Toyota WS fluid at 115 k km .
    Done both front hub assembly 2 months ago.
    Oil change every 8000 km
    New brakes rotors front and rear 1 month ago
    No other problem in the car, runs perfect.
    Your input please .

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    #1 scorpion1, Sep 15, 2018
  2. Grit

    Grit Senior Member

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    Vehicle:
    2012 Prius
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    Four
    Gravel in between underbody covers that rattles at certain speeds?
     
    #2 Grit, Sep 15, 2018
    Joele3 likes this.
  3. bisco

    bisco cookie crumbler

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    loose underbody cover or exhaust heat shield
     
    #3 bisco, Sep 15, 2018
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  4. jack black

    jack black Active Member

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    since you did a lot of work, did you drop a tool/bolt/screw/etc inside the engine compartment? it has happened to me and i had the same symptoms.
     
    #4 jack black, Sep 15, 2018
  5. scorpion1

    scorpion1 Junior Member

    Joined:
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    Location:
    Ontario. canada
    Vehicle:
    2010 Prius
    Model:
    ----Canada----
    No nothing is dropped in engine compartment, it rattles only around 100- 110 km speed, when it becomes constant, I remove foot off gas pedal and the Rattling goes away, after a while it come back again.
    No rattling on city streets.
    My guess is transmission or engine.
    I have no engine oil burn. Since last year I have done 3 oil changes, not even a drop was added between oil changes.
    I am planning to add catch can this fall , may be it helps.
    wondering if any body else having same issue???

    Posted via the PriusChat mobile app.
     
    #5 scorpion1, Sep 16, 2018
  6. jack black

    jack black Active Member

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    then do the entire EGR cleaning. could it be the rattling passenger side fender clip?
     
    #6 jack black, Sep 16, 2018
    Sathump likes this.
  7. Sathump

    Sathump Junior Member

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    Vehicle:
    2013 Prius
    Model:
    II
    I think Jack told you the answer

    If its at low engine loads the EGR valve is open, but if any of those tiny ports in the manifold are clogged you'll have a knock in those conditions.

    Y'all know you can block the EGR port and disconnect the plug to the valve. It'll just be a supper reliable 1.8l all the time.
     
    #7 Sathump, Sep 20, 2018
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