Loud knocking from engine once at startup

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by CapnBio, Feb 17, 2021.

  1. CapnBio

    CapnBio Junior Member

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    Hey everyone.

    So I have seen other people have similar issues that they heard knocking when they start it up cold and etc. So my issue is i have started my car one morning (after sitting all night from 8pm), and it started perfectly fine and engine kicked in like normal. Then I moved it into the driveway from the side of the street, maybe like 20 feet.

    So after having the prius sit for roughly a few hours, i start up the car and i heard really loud knocking noise and the engine shaking violently and I felt the car also shaking a bit too as a result of this i immediately turned off the car. Afterwards i turned on the car and the engine turned perfectly fine without the loud knocking.

    I drove home perfectly fine (roughly 30 miles) it did not give any problems at all. It's been a few days after this incident and nothing has happened since. My worry is with the little research I've done. I need to change the head gasket. Is this something i need to get done? I would like to see what I need to get done so I can fix it up and not have this for another million miles (figuratively) to make my car last a while longer.

    It's a 2014 prius two. Currently has 136k miles i had never had any problems until now. I haven't even changed the spark plugs...
     
  2. chronon

    chronon Active Member

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    i dont haveloud knocking but i have the loud timing chain startup on camry hybrid (that is a 2.5l engine) ..
    it does this about a second or 2 or 3 depending how long it sat .. full synth .. oil full .. dealer caused this condition by overtightening oil filter cartdridge cap .. -- when i went to remove it cracked and i drove with it leaking oil unknownst to me .. i spent $30 to get a metal cap ..

    dealer fix was overfill oil level ... --- this is a $1000 dealer repair to fix the timing chain tensioner ..
     
  3. CapnBio

    CapnBio Junior Member

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    Holy smokes, that's just crazy. My timing chain hasn't given me issues at all. I know that for sure. It's very quiet from what I can tell. I am trying to see what I can do before i actually take it to the dealer for diagnostics. But the gasket i can fix myself for sure. Just trying to do preventative maintenance just in case of anything.
     
  4. bisco

    bisco cookie crumbler

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    this is the classic unburned hydrocarbos detonating because you shut the car down cold.

    no worries, but try to let it shut itself off in the future, before shutting down with the power button. that way, it goes through the whole warm up cycle.
     
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  5. Grit

    Grit Senior Member

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    o_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_Oo_O
     
  6. Mendel Leisk

    Mendel Leisk Sand Pounder

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    It’s a bit of a design fail, but yeah: cold starts and near immediate shutdowns have been triggering subsequent start-up knock. One consolation: it’s likely not head gasket.

    Still, at 136k I’d clean complete Exhaust Gas Recirculation AND intake manifold, ASAP. Oil catch can wouldn’t hurt too.
     
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  7. CapnBio

    CapnBio Junior Member

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    I'll take a look to cleaning it up this weekend. What would i use to clean the egr and intake manifold? Not sure how it clean the oil catch can either.
     
  8. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Info:
    Bad Flywheel | PriusChat
     
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