How to drain inverter coolant?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by lastradakiwi, Jun 12, 2025 at 9:53 PM.

Tags:
  1. lastradakiwi

    lastradakiwi New Member

    Joined:
    Aug 17, 2024
    21
    3
    0
    Location:
    Fairfax, Virginia
    Vehicle:
    2017 Prius c
    Model:
    One
    Hi everyone,

    I have a 2009 Prius (Gen 2) and I’m getting ready to drain and refill the inverter coolant. I recently replaced the inverter pump, and I want to make sure the whole system has clean coolant and no air bubbles.

    I’m a bit confused about where exactly to drain the coolant. I know there is a drain plug under the car, but where exactly is it? I don't want to accidentally drain the transmission fluid instead of the inverter coolant! If there’s a plug, what socket size do I need to remove it? Will I need a breaker bar?

    Also, is there a socket that fits the bleeder valve for the inverter system? I tried using a 10mm socket, but it wouldn't go all the way down. Do I need a deep socket instead?
     
    #1 lastradakiwi, Jun 12, 2025 at 9:53 PM
  2. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    8,173
    4,165
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    I've attached the repair manual excerpt, which shows the bolt. It is a 24 mm bolt. The Transaxle fluid drain is a (10 mm, don't quote me) hex (or allen key) inset bolt (same Idea as a machine screw) so your 24 mm socket won't fit that one.
    24 mm
    Most likely, if this is the first time it has been undone, and you might need a handle extension as well.
    No, it is better to slip on a closed-ended wrench before attaching your drain hose. A socket is not practical for this.
     

    Attached Files:

    #2 dolj, Jun 13, 2025 at 10:34 AM
  3. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    11,982
    2,115
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    The pH test strips of your original coolant that's in that container. Should show good . Top it up . Save for real repairs . Now if the fluids green from mix of orange and blue coolants by all means go ahead
     
    #3 Tombukt2, Jun 13, 2025 at 12:46 PM
(You must log in or sign up to post here.)