1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Louder hum when Ready or Ig-On

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by danjan101, May 14, 2012.

  1. danjan101

    danjan101 Junior Member

    Joined:
    Apr 24, 2012
    5
    0
    0
    Location:
    Los Angeles
    Vehicle:
    2005 Prius
    Model:
    N/A
    2005 Prius, 50K. Newly purchased two weeks ago. Last night, driving into my garage with the ICE off, noticed a noticeable electric or electronic-sounding hum from the engine compartment. With the hood up and looking toward the engine from the front of the car, noise comes from the right side of the engine compartment, to the right of the inverter cover.

    The noise, a loud hum, appears when pressing the Power button and the brake pedal. It also appears when pressing the Power button twice without pressing the brake pedal. When starting up the car, the hum lowers in pitch significantly (though not in volume) as soon as the Park button is pressed.

    When I bought the car, I brought it in to the dealership for a complete checkup. They replaced the inverter coolant pump under the recall notice. Don't know if that's significant. I opened the coolant reservoir cap last night with the motor on, and noticed movement inside, so it appears to be working fine.

    I'm concerned about the louder humming noise because for the past two weeks it wasn't there (or was at a low enough threshold to be effectively inaudible to me). I'm very sensitive to sounds from the car at the moment as it's new to me, and this new sound immediately caught my attention. There are no warning lights or error codes shown.

    Wondering if this falls under the normaloid spectrum of behaviors for this car, or if it presages some sort of breakdown. I found a few brief mentions of something similar in various threads, but never found an answer, unfortunately. Any help would be very gratefully received.

    Dan J.
     
    #1 danjan101, May 14, 2012
  2. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,804
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    The area in question your talking about is where the Inverter pump is located. Sounds like they did not get all the air out of the coolant loop.

    Listen to it carefully it should have a very steady buzz like an aquarian pump not a buzzz then gurlge.
     
    #2 edthefox5, May 14, 2012
    1 person likes this.
  3. danjan101

    danjan101 Junior Member

    Joined:
    Apr 24, 2012
    5
    0
    0
    Location:
    Los Angeles
    Vehicle:
    2005 Prius
    Model:
    N/A
    Thank you most kindly, edthefxo5; your answer is greatly appreciated.

    The area does, in fact, have a steady buzz, with no gurgles. It's just that is has become much louder all of a sudden, from a faint whisper in the background before, to a loud-ish humming now, clearly audible inside the cabin. I wonder if this is a function of a normal pump going through a break-in period, or whether it's simply a case of a faulty unit installed by the dealership.

    In your opinion, with no error codes or warning lights, is it worth taking it back to the dealership, or will they shine it on in the absence of other indicators?

    Thank you again for your helpful reply.

    Dan J.
     
    #3 danjan101, May 14, 2012
  4. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,804
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Your welcome.
    Its clearly the Inverter pump. I wonder if its just a new bad pump bad being thats its very loud. My original 07 pump is very quiet in comparision.

    Bring it back to the dealer. Not sure if they will charge you a diagnostic fee. Most are around $125.

    Or

    I don't know your skill set but if was me I would buy a gallon of SLLC (Super Long Life Coolant $20 ) and try giving it a burp or two. Its really easy to bleed and requires very little tools. There's a few You Tubes on it and its easy as they provided a bleed valve. All you need to do at this point is open the bleed valve and see if any air comes out.

    Take the black plastic valence cover off the top front of engine. The cover that prevents you from seeing the front of the radiator. Using a phillips screwdriver turn the screws while you snake your hand behind the screw and push the screw out with your finger.
    Screw comes right out. Remove cover.
    Just to the front of the inverter and on the left side you'll see a bleeder valve. Thats the valve you have to open.

    Here's the one hard part. The valve is on really really tight and you must hold the valve body itself while you loosen the valve or you may snap the whole deal off. Another words its hard to torque the valve loose without bending the whole valve itself. You'll see what I mean. And adjustable wrench on the body works good.

    Once valve is loose just let it bleed out. You'll see some coolant come out to. Let it bleed till just solid coolant comes out no spitting. Bleed then close it and wait a while. Bleed a little, close it and wait again. This is while the car is in ready by the way with the pump on. The gallon of SLLC you bought will be used to top off the reservoir. Don't let the reservoir get too low during the bleeding.

    Btw, with that valence cover off its a good time to clean the bugs and dirt out of the AC condenser which is the shiny radiator in front of the main radiator. Go to Home Depot and buy a spray can of AC Condenser cleaner. Its the blue can. Get a water hose and hose the front of the car down like the bumper and grill as you don't want this cleaner to get on the paint. It won't hurt the paint but will strip the wax.
    With it wet it will not attack the wax. Hose the radiator down good with the spray cleaner. Let it sit then rinse it off and the entire bumper in case some soap got on it. Should look like shiny new aluminum when you done. You won't believe how much cooler your ac will run.

    Good Luck.
     
    #4 edthefox5, May 15, 2012
    1 person likes this.
  5. danjan101

    danjan101 Junior Member

    Joined:
    Apr 24, 2012
    5
    0
    0
    Location:
    Los Angeles
    Vehicle:
    2005 Prius
    Model:
    N/A
    Excellent and informative advice, edthefox5. Thank you again, I feel much better about this now.

    Dan J.


     
    #5 danjan101, May 15, 2012
  6. GrumpyCabbie

    GrumpyCabbie Senior Member

    Joined:
    Dec 14, 2009
    6,722
    2,121
    45
    Location:
    North Yorkshire, UK
    Vehicle:
    2010 Prius
    Model:
    III
    Are you sure it's not the a/c compressor? On a hot day when first turned on it will hum alarmingly loudly. I thought there was something wrong with my car but it is normal.

    Try switching the a/c on and off when the hum is occuring to see if that solves the issue?
     
    #6 GrumpyCabbie, May 15, 2012
  7. danjan101

    danjan101 Junior Member

    Joined:
    Apr 24, 2012
    5
    0
    0
    Location:
    Los Angeles
    Vehicle:
    2005 Prius
    Model:
    N/A
    thank you, GumpyCabbie. My A/C was off, however. Will try with it on.
    Dan J.
     
    #7 danjan101, May 15, 2012
(You must log in or sign up to post here.)