Engine Overheating and Coolant Overflow

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by niftypsycho, Apr 7, 2026 at 3:12 PM.

  1. niftypsycho

    niftypsycho New Member

    Joined:
    Today
    1
    0
    0
    Location:
    United States
    Vehicle:
    2012 Prius
    Model:
    III
    About 3 weeks ago I was driving on the expressway when my temp light came on and white smoke started erupting from under the hood. I took it in, and they said it was an issue with the headgasket but most places around me won't service hybrids.

    I ended up doing the headgasket myself; the headgasket was definitely blown in places so it wasn't a total waste of time, and drove it around for a few days after with no issues. Today the same thing happened, white smoke from under hood and temp light but not as severe.

    I'm really at a loss, and what I'm seeing from people is that it could be a few things like thermostat, radiator cap, etc. This car has a reservoir with the OEM cap on it still.

    Additionally, the hot air will come on after a few minutes of driving but went back to cold when I was on the expressway before this happened.

    All in all I replaced the headgasket, engine bolts, and water pump.
    I did NOT replace the thermostat, or any of the hoses.

    Any advice is appreciated
     
    #1 niftypsycho, Apr 7, 2026 at 3:12 PM
  2. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    13,088
    5,308
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    What was your sense of the coolant system when draining it and refilling it?

    Any chance something is clogged or thermostat was faulty?

    Is it possible you or previous owner used some type of gasket sealer product in the coolant in the past?

    In general a failed water pump or headgasket or both doesn't create white smoke in the engine compartment...

    Any sense of where specifically it's coming from?
     
    #2 PriusCamper, Apr 7, 2026 at 8:27 PM
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

    Joined:
    Oct 17, 2010
    60,951
    41,928
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    How many miles on it, and have you ever cleaned the EGR system?
     
    #3 Mendel Leisk, Apr 7, 2026 at 9:00 PM
  4. CR94

    CR94 Senior Member

    Joined:
    Dec 2, 2014
    2,756
    1,208
    0
    Location:
    Northwestern S.C.
    Vehicle:
    2011 Prius
    Model:
    Two
    Another basic question: Has coolant level dropped since the head gasket replacement?
     
    #4 CR94, Apr 7, 2026 at 9:05 PM
  5. Brian1954

    Brian1954 Senior Member

    Joined:
    Jan 31, 2021
    2,416
    970
    0
    Location:
    South Central PA, USA
    Vehicle:
    2011 Prius
    Model:
    III
    What engine water pump did you buy? Where did you buy it from?
     
    #5 Brian1954, Apr 7, 2026 at 9:10 PM
(You must log in or sign up to post here.)