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Hard knock on start up

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Logantoman, Jul 20, 2021.

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  1. Logantoman

    Logantoman New Member

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    I got a 2010 Prius 1.8. No it’s not rod knock. Had a problem on start up that sounds from the transmission side. Hard knocking/clanking. It’s also drinking coolant. I bought the car thinking it needed a head gasket. Tore it down, swapped it and put it back together. Cylinder 2 was the cleanest cause it burnt the coolant inside it. Thought I could see the failure on the gasket. Felt confident. Fired it up today and it’s still got a knock on start up but went away as it got warm and keep running it. But I’m still loosing coolant. And the oils getting milky again. I didn’t see any cracks in the block when I was doing the repair. I’m at the point I’m just gonna swap the motor for the coolant problem but I don’t know if something in the trans is bad or if those 2 things correspond with eachother. If it’s 2 separate problems I’m just gonna tear it down and part it
     
    #1 Logantoman, Jul 20, 2021
  2. bisco

    bisco cookie crumbler

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    maybe the head is warped? did you clean the egr circuit?
     
    #2 bisco, Jul 20, 2021
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  3. Logantoman

    Logantoman New Member

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    I left it completely alone and intact just hoses and harness I took off. Just unmounted it
     
    #3 Logantoman, Jul 20, 2021
  4. Logantoman

    Logantoman New Member

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    I left it completely alone and intact just hoses and harness I took off. Just unmounted it. It’s a hard knock the shakes the entire motor. It’s right under the egr or kinda behind it. I didn’t check the head but it could be. But it’s sounding like 2 separate problems so I think I’m just gonna part it
     
    #4 Logantoman, Jul 20, 2021
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  5. mr_guy_mann

    mr_guy_mann Senior Member

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    It's likely that your engine problem is causing a misfire on startup, that results in the "damper" smacking its internal stops. (The damper is a spring loaded coupler that reduces the torsional - twisting vibrations from the engine from affecting the transmission drive motors). Misfire causes much bigger twisting shocks that the damper can't absorb.

    You could have a cracked head or block casting, or the head was warped . Usual diagnostic method I have is to use a special hand held pump that replaces the radiator cap and pressurize the cooling system. Remove the spark plugs and look inside the cylinders with a videoscope to see where the coolant leak is.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Jul 20, 2021
  6. ChapmanF

    ChapmanF Senior Member

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    Not just the damper; any gear train always has some play in it. and a misfiring engine will bang all the gears through it, first one way and then the other, and sound like the forge of Hephaestus.

    That can happen whether or not the damper is hitting its stops, and I don't have much reason to think that it is. The bouncing back and forth is enough. Things would sound worse if the damper weren't there, and will sound worse if this goes on long enough for the damper's springs to break.

    Occasionally, people have popped off the little hand-hole cover into the bell housing and felt around in there, and come out with pieces of spring.
     
    #6 ChapmanF, Jul 20, 2021
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  7. Logantoman

    Logantoman New Member

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    Bout what it sounds like. Literally like throwing a rod over and over and shaking the entire thing, Probably that with a warped head. Thank you. I’ll give the hand hole a shot but I got a feeling they are broken with how much I was trying to run it haha
     
    #7 Logantoman, Jul 20, 2021
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    How many miles?
     
    #8 Mendel Leisk, Jul 20, 2021
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  9. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    They use those funny metric measurements on the OP's side of the pond.....

    +1 on the egr circuit.
     
    #9 ETC(SS), Jul 20, 2021
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Road signs are apparently in mph, can’t get a straight answer from Google regarding odo units. Either kms or miles will do; the conversion is pretty easy (roughly 5/8 or 8/5).
     
    #10 Mendel Leisk, Jul 21, 2021
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  11. ASRDogman

    ASRDogman Senior Member

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    Did you take the head to a machine shop and have them check the head to see
    if it was warped or cracked? Since the oil is milky, that's probably the source.
    There is also the posibility the block is cracked.
    Did you use a new head gasket?

     
    #11 ASRDogman, Jul 21, 2021
  12. Logantoman

    Logantoman New Member

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    Around 240,000 buts it’s been all highway from about 140ish
     
    #12 Logantoman, Jul 21, 2021
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  13. Logantoman

    Logantoman New Member

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    No just did the repair. Thought I could see failure in the gasket around a coolant but I’m wrong. Still having the clanking problem at start up but this was happening right before it started drinking coolant and I put a new head gasket
     
    #13 Logantoman, Jul 21, 2021
  14. mr_guy_mann

    mr_guy_mann Senior Member

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    I assume it's a little more than "just" gear train backlash, otherwise any 4 cylinder manual transmission car would sound like a Prius when it misfired (which they don't). Maybe the additional inertia of MG1 together with the springs in the damper (possibly weaker when compared to a normal M/T car?).

    Posted via the PriusChat mobile app.
     
    #14 mr_guy_mann, Jul 21, 2021
  15. ChapmanF

    ChapmanF Senior Member

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    It would sound exactly like a Prius, if the 4 cylinder manual transmission car also contained two large motors being actively controlled by a computer that was trying to rotate them in synchronization with the misfiring engine.

    There's a bit more on that at the end of this article.
     
    #15 ChapmanF, Jul 21, 2021
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    "The School of Hard Knocks"? :D
     
    #16 Mendel Leisk, Jul 21, 2021
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  17. ASRDogman

    ASRDogman Senior Member

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    You should always check it when you have it off.
    You said you bought the car knowing it had a head gasket failure, but why did it fail?
    How long did the previous driver drive? Did water get in the cylinder and bent a rod?

    You should remove the wiper assembly, remove the coils and plugs and look inside with a bore scope.
    Do you see water? Then pressure test the coolant system. Under pressure you might be able to
    see the fluid leaking into the cylinder.

    And why the plugs are out, put a stick inside each cylinder and rotate the engine to tdc and measure and make
    a mark on the stick, or whatever you use. If you start at #1, go to #4, it should be the same.
    Then rotat the engine and bring #2 and 3 to tdc, and measure the same way. All 4 should be the same.
    If one is not the same, then the rod is bent.

     
    #17 ASRDogman, Jul 21, 2021
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