Loud clunk and loud engine noise in HV mode

Discussion in 'Prime Technical Discussion' started by MommysPrius, Sep 8, 2019.

  1. MommysPrius

    MommysPrius New Member

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    Hello everyone,

    My Prime is just over 2 months old, and I've noticed the last handful of times I've turned on the HV mode that it makes a clunk sound and then the engine is loud. Like I'm using the air conditioning on high and engine is working hard. It gets quiet after a few minutes. This test is usually when I'm sitting in the parking lot trying out the HV mode or at a red light.
    Still wondering if this is normal. Is this possibly because I don't use HV mode very often and engine just needs to warm up?
    It didn't do this the first time I picked up the car. I tried putting it on HV mode for fun on the way home from the dealership and I remember thinking that the transition from EV to HV was seamless.
    Couldn't even notice the difference.

    What's wrong with my Prime now???

    Thank you in advance!
     
  2. schja01

    schja01 One of just a few in Chicagoland

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    I had exactly the same experience a few times when the car was not used in HV mode for a while. Now I use HV a few minutes every week and it hasn’t happened again.
     
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  3. mr88cet

    mr88cet Senior Member

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    I can’t recall having heard that, based upon your description, although I too comparatively rarely use HV mode.

    The only really ... disconcerting ... noise I’ve heard, very roughly along those lines, is (I’m pretty sure) from the traction-control system. It happens when I take off a little fast around a tight right-turn bend. It’s hard to describe, but it’s more or less a simultaneous clack and crunch sort of sound. Reasonably loud. It’s not repeating like the sound you’d expect to hear from a bad CV joint.

    Presumably that happens in hybrid mode too, although I can’t recall having heard it, again since I mostly drive in EV mode. So anyway, I can’t comment upon whether the engine sound changes afterward, but probably not.

    Anyway, it might be worthwhile to file a warranty claim, although maybe not immediately. Reasonable of you to ask around for some data.
     
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  4. jb in NE

    jb in NE Senior Member

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    I have noted that a cold HV start is always more noticeable when stopped than when moving. When the engine starts it runs for at least 3 minutes to warm up, and the engine sounds very loud compared to EV mode, particularly when stopped.

    What you describe appears normal.
     
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  5. john1701a

    john1701a Prius Guru

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    ...especially when you equate that loud clunk to the vent for the radiator opening.
     
  6. jb in NE

    jb in NE Senior Member

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    Which vent would be opening at engine start?
     
  7. john1701a

    john1701a Prius Guru

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    The only vent that opens & closes feeds everything for the engine compartment. (And it really doesn't ever close entirely.) It's primary purpose is for heat retention. But if the engine needs to breath more during the startup process, opening for that seems quite reasonable. After all, you fan a fire to get the flames up.
     
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  8. jb in NE

    jb in NE Senior Member

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    I believe the shutter vents open in response to a need for cooling, not for engine air intake. You would want as little cooling as possible during engine warmup.
     
  9. john1701a

    john1701a Prius Guru

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    Generically, yes. But the car knows when it is stationary no air will be pushed through. And we know for a fact the shut doesn't take place until driving begins.
     
    #9 john1701a, Sep 8, 2019
    Last edited: Sep 8, 2019
  10. jb in NE

    jb in NE Senior Member

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    Perhaps @Elektroingenieur will have some information from the technical manuals regarding the grille shutter operation.
     
  11. john1701a

    john1701a Prius Guru

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    My anecdotal observations (never bothered to actually measure) is the shutter close occurs at either by a speed or time trigger. It's fairly consistent when leaving both home and the coffeeshop in EV mode.
     
  12. MommysPrius

    MommysPrius New Member

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    I think I'll try to run the HV mode a bit more often then. A few minutes every week as yourself. Just to make sure everything is in proper working order...
     
  13. schja01

    schja01 One of just a few in Chicagoland

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    I just put it in HV mode until the engine starts then switch back to EV mode. The engine will run for 3 minutes or so depending on the outside temp. Longer in winter shorter in summer. Doing so kills your ECO Scoreboard Fuel Consumption MPG but I’ve long since stopped concerning myself with that.
     
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