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No More Coolant Pump Noise?

Discussion in 'Gen 2 Prius Main Forum' started by ajayre, Jan 14, 2012.

  1. ajayre

    ajayre Junior Member

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    Every time I turn my Prius on and off I hear a whirring-pumping noise. I believe this is the thermo coolant pump (please correct me if I am wrong).

    A couple of weeks ago the dealer replaced a slowly failing 12V battery and replaced the brake discs and pads.

    Now the whirring-pumping noise is gone! Should I be worried? What could have changed?

    Thanks, Andy
     
    #1 ajayre, Jan 14, 2012
  2. Hal W

    Hal W New Member

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    I believe the pump noise you are hearing is the pump that fills the thermos bottle. The 12v should have nothing to do with the pump noise! Hal
     
    #2 Hal W, Jan 14, 2012
  3. ajayre

    ajayre Junior Member

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    You mean the pump noise I am no longer hearing. That is my question - should it ever stop unless something is broken?

    Andy
     
    #3 ajayre, Jan 15, 2012
  4. puckdrop

    puckdrop Junior Member

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    Correct me if I'm wrong.. but I read somewhere that the UK version doesn't have the coolant thermos flask ? The sound you're hearing is more likely to be the hydraulic brake circuit pressure charging up ?
     
    #4 puckdrop, Jan 15, 2012
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  5. ajayre

    ajayre Junior Member

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    That would be interesting because the sound disappeared after the brake job! Hmm...

    Andy
     
    #5 ajayre, Jan 15, 2012
  6. uart

    uart Senior Member

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    Could be the brake accumulator pump. That runs whenever the accumulator needs pressure.
     
    #6 uart, Jan 15, 2012
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  7. qbee42

    qbee42 My other car is a boat

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    The UK model does not have the thermos bottle, so no transfer pump. Most likely you were hearing the brake accumulator pump. It makes more of a ratcheting sound. If you want to hear it, press and release the brake pedal three or four times. That will use up the brake pressure and force the pump to run.

    Tom
     
    #7 qbee42, Jan 15, 2012
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  8. Hal W

    Hal W New Member

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    Well I guess that is why he can't hear it, but he could before the 12V change!!!!I never even notice location! Another 60's moment.. Hal
     
    #8 Hal W, Jan 15, 2012
  9. uart

    uart Senior Member

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    No not the 12V battery, they also did the brake pads, they probably did the brake fluid as well. There could be a little less movement now in the calipers or some other subtle change that is triggering the accumulator pump a bit less.
     
    #9 uart, Jan 15, 2012
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  10. David Beale

    David Beale Senior Member

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    It's probably because of both fixes. The 12V battery replacement makes the brake accumulator pump more effective (not trying to pump on low voltage) so it only runs for a sec. or so. The brake pad replacement stopped it because it no longer has to move the pads as far.
    I'll bet it still "burps", it just doesn't do so for a long period.
     
    #10 David Beale, Jan 15, 2012
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  11. ajayre

    ajayre Junior Member

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    Previously I heard the noise after every time I turned the car off (as well as when turned on). That would still be the brake accumulator pump?

    It's reassuring that the noise going away actually means the car is working better!

    Thanks, Andy
     
    #11 ajayre, Jan 15, 2012
  12. Britprius

    Britprius Senior Member

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    How much did the dealer charge for disc and pad replacement. I am about to change mine and have sourced all the parts front and rear for £70 and will change them myself. The pads still have about 50% life left but discs are very rusty so will change everything. Mileage 80K.
     
    #12 Britprius, Jan 15, 2012
  13. ajayre

    ajayre Junior Member

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    460 for parts and labour. It's expensive but I don't have the skills or equipment to do it myself...

    If I pump the brake pedal I can get it to make a whirring noise. Also if I turn it off with the brake pedal pressed. But it doesn't sound quite the same as the noise I was thinking off. So maybe my car was sick for a long time and I didn't know it.

    Andy
     
    #13 ajayre, Jan 15, 2012
  14. uart

    uart Senior Member

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    Maybe the new brake fluid quietened it down? :confused:
     
    #14 uart, Jan 15, 2012
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