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Howling noise coming from ICE

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Jzak, Mar 7, 2020.

  1. Jzak

    Jzak New Member

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    Hello all, this is my first post on this forum. Have been a long time lurker and usually good at searching for answers instead of posting but I am stumped at my current situation.
    06 Prius 387k on it
    Has been a great car....

    Just yesterday after being on the highway for about an hour I started to notice a slight howling/whining noise from the car at ice idle and at low engine speeds. (After about 30 mph the noise goes away or I can't hear it)
    The noise only is made when the ice is running. When the ice shuts off the noise goes away. Driving on electric there is no sound. But as soon as the ice engages to help the noise comes back.
    I have pulled off the water pump belt and started the car and it still makes the noise.
    It seems like it is coming from the front of the engine near the belt and crank.
    I thought at first it was a bearing but the tensioner pulley and water pump all check out and I want to think it's something internal in the engine.
    I do not have any new codes. Currently just have a p0420, p1121 and p1116.
    The cat has been gutted and is the reason for the p420 code. (Haven't fixed it yet)

    If anyone has any ideas I would greatly appreciate it.
    Also considered at one time that it was a vacuum leak but there are no hoses I see that are bad.
    The car drives fine and doesn't seem to have any issues other than this noise.
     
    #1 Jzak, Mar 7, 2020
  2. JC91006

    JC91006 Senior Member

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    How did you verify the water pump, belt, pulley was not making the noise? I would bet those are the problem areas
     
    #2 JC91006, Mar 7, 2020
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  3. Jzak

    Jzak New Member

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    I pulled the belt off and put the car in maintenance mode.
     
    #3 Jzak, Mar 7, 2020
  4. ChapmanF

    ChapmanF Senior Member

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    Do you have a mechanic's stethoscope handy?
     
    #4 ChapmanF, Mar 7, 2020
  5. Jzak

    Jzak New Member

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    I did and that is why I felt it might be a water pump bearing. The noise was coming from the pump. However removing the belt was not helpful. Is the pressure in the system that high from the electronic pumps that they can still move the mechanical water pump?
     
    #5 Jzak, Mar 7, 2020
  6. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    Nice run you've had there. Does the noise change or increase as the RPMs rise?
     
    #6 SFO, Mar 7, 2020
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  7. Jzak

    Jzak New Member

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    Yes it does.
     
    #7 Jzak, Mar 7, 2020
  8. valde3

    valde3 Senior Member

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    So it can't have anything to do with coolant flow. As the noise changes with engine RPM and is there without belt. So in the front of the engine there are oil pump, timing chain, bearings, and seals. If there are no bad oil leaks, no codes related to vvt-i (oil pressure), or bottom end noises (also oil pressure) it would sound like it has to be related to timing chain.

    If you remove the valve cover you could see part of timing chain. You could also try to move the (non vvt-i) exhaust cam back and forth to see if the timing chain is lose. Ratchet mechanism in the chain tensioner should keep it pretty tight when engine is not running. For the chain to make that sort of noise it would have to grind on something. Is it would have to be loose enough to touch something or chain guide plastic parts that chain is riding on would have to be broken or worn through.
     
    #8 valde3, Mar 8, 2020
  9. Jzak

    Jzak New Member

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    I was thinking that it might be related to timing chain and guides.
    I have not pulled the valve cover but I drove it today because I had to do some travel and the noise is now gone.
    The car needs an oil change as it just hit the change interval.
    I talked to a friend last night's that has rebuilt several of these 2nd generation Prii, and he told me that coolant would still flow through the system even if the mechanical water pump was disconnected. The other motors in the system would still spin the water pump.
    He believes that it is the water pump making noise but I was thinking more of timing chain guides.
    But now the noise is gone so I don't even know what to think.
     
    #9 Jzak, Mar 8, 2020
  10. JC91006

    JC91006 Senior Member

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    Only thing that moves the water pump is the belt and pulley. Without the belt, water pump can't move.
     
    #10 JC91006, Mar 8, 2020
    SFO and Raytheeagle like this.
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