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Severe Knock/Rattle (maybe from transaxle?)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by tvpierce, May 24, 2016.

  1. tvpierce

    tvpierce Senior Member

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    My wife called today on the side of the road with a strange knock/rattle sound from the front (engine/trans/etc) along with an apparent loss of power. (no prior warning signs -- just started) She wisely stopped driving, then called me, and we decided it would be wise to have it towed home.
    (Let me take a moment to praise my wife who has always been extraordinarily attentive to the mechanical operation of her vehicles. I've always been the fleet mechanic, and if she has ever experienced anything out of the ordinary, she contacts me immediately. She's not frantic or unreasonable -- in fact she's fiercely independent -- she's simply a conscientious person, and I love that about her.)

    So we get the car home and I begin looking into what's going on. Was hoping it would be something simple like a motor mount or exhaust shield... no such luck. Everything externally seems fine.

    Video here taken from under the car:


    Judging by the sound and the feel (by placing my hand) it seems the problem is in the transaxle.
    Not sure where to go from here. Would really appreciate any input.

    Thanks!
     
    bisco likes this.
  2. JC91006

    JC91006 Senior Member

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    Check your oil, then check/change your spark plugs
     
    #2 JC91006, May 24, 2016
    Last edited: May 24, 2016
  3. bisco

    bisco cookie crumbler

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    how many miles on her?
     
  4. edthefox5

    edthefox5 Senior Member

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    The car probably eats engine oil and was allowed to run so low on oil the check engine light came on from lack of oil pressure. Just one of those real low oil events apparently damages the piston rods and then comes the engine knock. Transaxle does not knock. Motor is toast. Start shopping for new long block.
    Lots and lots of posts lately about this very issue. All being at 150K plus miles.
     
  5. JC91006

    JC91006 Senior Member

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    There's a video, I think from boulder hybrid, same thing needs spark plug
     
  6. tvpierce

    tvpierce Senior Member

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    Hi all. Thanks for the quick responses.

    Sorry... I should have included more of the vital stats.

    143K miles. Oil level is perfect (just under the full mark)... exactly where it was when I changed it about 1K miles ago.

    I've had this car for about 45K miles, about 14 months. It gets regular 10K mile oil changes with full synthetic. It only burns about a half a quart over 10K miles, so this engine is tight as a drum.

    I don't have a service record from the previous owner, but I'm also not a newbie mechanic, and I've been all over/under this car -- it's in excellent condition. That's not to say that there can't be a serious problem with it... just that it's not some clapped out piece of junk on its last legs.

    EDIT: Forgot to add: this knocking sound started without warning. She drove 150 miles on the highway, made two sales calls, and this started when she was on her way to her next account.

    Again, thanks!
     
    #6 tvpierce, May 25, 2016
    Last edited: May 25, 2016
  7. tvpierce

    tvpierce Senior Member

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    Funny you mention this. That video popped up when I posted mine on Youtube.



    It does sound exactly like that. What's the theory on cause and effect? I can't in my mind figure out how faulty plugs could cause that knocking.

    Plugs were changed at 100K miles with NGK iridium plugs. I bought them online, and they were among a long list of plugs that fit the Prius. They were not, however, the slightly more expensive plug recommended by folks on Prius Chat.

    Was planning to buy some Denso SK16R11, or NGK IFR5A11 at the parts store today.
     
    #7 tvpierce, May 25, 2016
    Last edited: May 25, 2016
  8. tvpierce

    tvpierce Senior Member

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    UPDATE: Just changed the spark plugs to NGK IFR5T11... no change.

    And another set of symptoms I forgot to mention that may be quite important: She described a "bogging/lugging/lack of power" when this happened, and the car emits a strong sulfur odor while it's running.
     
  9. JC91006

    JC91006 Senior Member

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    Bad gas? Bad coils? Clogged injector? Faulty throttle body? Clean it recently?

    It does sound really bad
     
  10. tvpierce

    tvpierce Senior Member

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    Hadn't fueled up in a couple days, so bad gas seems unlikely. Have not cleaned the throttle body.
     
  11. JC91006

    JC91006 Senior Member

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    I don't think it's the throttle body, but clean it anyways, since you're checking that whole area
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Assuming you've popped the hood, this would NOT be a possibility, but: hood support rod fell down, rattling on engine?

    (This actually happened to me, after a service visit.)
     
    #12 Mendel Leisk, May 25, 2016
    Last edited: May 25, 2016
  13. valde3

    valde3 Senior Member

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    Put it to neutral (make sure battery has enough bars) and listen to the sound of the engine. Prius base idle

    When Prius is in gear (including park) engine operating and hybrid system are connected and it’s hard to tell what the problem is. But with it idling in neutral engine idles just as every other engine and it should be easy to tell if it's running on all 4 cylinders. And you can also easily do power balance test by unplugging the coils.
     
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Is the check engine light, or any other warning light on?
     
  15. tvpierce

    tvpierce Senior Member

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    Excellent point! That would help isolate the noise. Will try that tomorrow morning.
     
  16. tvpierce

    tvpierce Senior Member

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    Yes, the CEL is on.

    i tried unhooking the #1 coil in an effort to diagnose the problem, that resulted in the "triangle of death".
     
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Most likely you have an engine misfire and not a transaxle issue. If the plugs are good then either a spark igniter or fuel injector is bad.
     
  18. johnnyb588

    johnnyb588 Member

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    I'm in agreement that this does not seem transaxle related.

    Your account of your regular oil changes and current state of oil would lead me to believe that it is also unlikely you have experienced any sort of catastrophic failure/binding. Most likely explanation, imo, is that you are misfiring, and that leads me to believe that it is either because of a failed coil or failed injector (probably not a plug since you just changed them). Getting codes would be helpful.

    ETA: Patrick beat me to it. FYI, pretty much #1 forum rule is "whatever Patrick say, it's probably right."
     
  19. Lucifer

    Lucifer Senior Member

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    I agree, agree with Patrick.
    Err, it's a gen2, the oil in those is always 7/8th's full or less, it get's into the parts above "maf filter", just pointing out
     
  20. edthefox5

    edthefox5 Senior Member

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    Put the car in base idle and then get under the engine and listen. if its a blown bottom end you'll know as it will be pretty distinct banging.
    If its just starting it may not be too bad unless the motor is under load.
    The fact that its not throwing a misfire and triangle only cel has me puzzled. if blown bottom end it almost always will throw a misfire and many a desperate owner will chase that.
    Time to read the codes.