Loud thunk, thunk, thunk... at cold start up?!?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Hangfire, Aug 30, 2018.

  1. Hangfire

    Hangfire Junior Member

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    I place my foot on the brake, pushed blue button, lights, radio, and ac come on... after a few seconds the gas engine engages and a loud, THUNK, THUNK, THUNK, THUNK, sound comes from the engine compartment! I immediately shut the car off, get out and open the hood and restart the engine. The sound is coming from behind and under the electric motor for a couple of seconds then disappeared. It happened yesterday, only once, nothing out of the ordinary today.

    Has this happened to anyone else? I've tried search and could not locate anyone who has.

    Thanks!

    2015 with 35,000 mi.
     
    #1 Hangfire, Aug 30, 2018
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  2. bisco

    bisco cookie crumbler

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    have you come across any of the 'cold start noise' threads? i don't know if you're hearing the same sound, but those are caused by starting the engine, usually moving it around the yard, and shutting it down before the warm up cycle has finished, leaving unburned hydrocarbons in the intake manifold, causing detonation on the next start up.
     
    #2 bisco, Aug 31, 2018
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  3. Grit

    Grit Senior Member

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    Welcome to the knock club, membership continues to grow. 2015 members come this way to sign the petition to have toyota resolve the EGR design.
     
    #3 Grit, Aug 31, 2018
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  4. Mendel Leisk

    Mendel Leisk Senior Member

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    #4 Mendel Leisk, Aug 31, 2018
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  5. mjoo

    mjoo Senior Member

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    Wow 6 active threads all with the same problem... Someone needs to search for EGR

    Pixel XL ?
     
    #5 mjoo, Sep 3, 2018
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  6. Grit

    Grit Senior Member

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    No way, whose going to hand feed them then?
     
    #6 Grit, Sep 4, 2018
  7. Starship16

    Starship16 Senior Member

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    Why be snarky. The person is brand new and asked a simple question. If it bothers you, don't answer! Cut back on the Jim Beam so you don't get so cranky. :LOL:
     
    #7 Starship16, Sep 4, 2018
    Last edited: Sep 4, 2018
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  8. mjoo

    mjoo Senior Member

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    Just making an observation that the "Maintenance and Troubleshooting" forum is becoming an "EGR Maintenance and Troubleshooting" forum. Maybe sticky one of the EGR cleaning threads and add all symptoms and repair methods to it?

    Save the Jim Bean for a special occasion.
     
    #8 mjoo, Sep 4, 2018
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  9. Starship16

    Starship16 Senior Member

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    That's Ok. Maybe it's because that stinkin' EGR is such a major problem? And common problems often dominate a forum. No big deal. Keep up the good work, fellas. :)
     
    #9 Starship16, Sep 4, 2018
    Last edited: Sep 4, 2018
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  10. Lightning Racer

    Lightning Racer Active Member

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    @Hangfire said that the car has only 35,000 miles. It does not need EGR cleaning. EGR cooler carbon blockage doesn't get to be a problem until at least 100,000 miles, and probably more like 150,000 miles before issues will manifest. I wouldn't touch it before 100,000 miles unless there is a P0401 code. It's also a 2015, so it already has the improved EGR valve (part number 25620-37120 vs. old part number 25620-37110) which is less prone to sticking.

    A new poster won't know the proper search terms to use, and might not even make the connection between "thunk-thunk-thunk" and "knocking" that is covered by this stickied thread: NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10 | PriusChat

    You'd also have to read 700-800 posts in that thread before you realize that the initial post in the thread is outdated. The intake manifold updates mentioned do not fix the problem, and Toyota reversed that TSB. So, really, it's hard to blame a new poster for not being able to find where the problem is covered.

    The oil catch can is the real DIY solution in this case. See: Oil Catch Can, Eliminate that knock! | PriusChat
     
    #10 Lightning Racer, Sep 5, 2018
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  11. Hangfire

    Hangfire Junior Member

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    I didn't move the car other than pulling into the driveway the night before so I don't think it was unburned hydrocarbons... of course I could be wrong. Thanks for your response!

    Thanks for the welcome but I'm not sure if it was the EGR... it sounded deep and loud metal to metal.

    Wow! Lots of great info in your post... I really appreciate your understanding. I'll look into the Oil Catch Can vids on YT and check out the stickied thread here on PriusChat! Thanks!

    Thanks! I'll be sure to check out the links!
     
    #11 Hangfire, Sep 17, 2018
    Last edited by a moderator: Sep 17, 2018
  12. bisco

    bisco cookie crumbler

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    has it happened again?
     
    #12 bisco, Sep 17, 2018
  13. mjoo

    mjoo Senior Member

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    Yes. My point was that there should be stickied threads for EGR cleaning and OCC.

    The stickied "NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10 | PriusChat" doesn't mention the real solution (OCC) until page 45/49. There are almost 1000 responses to that thread. A really smart newbie will probably give up after the first 200 replies. Quoting @danlatu:
     
    #13 mjoo, Sep 18, 2018
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