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sudden head gasket failure - or something else?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Michael Evans, Mar 2, 2024.

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  1. Michael Evans

    Michael Evans New Member

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    2004 Prius
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    @rjparker Thank you again for the information! Please excuse the delayed response. I think I can hear the coolant pump running on shutdown with warm engine, and also on startup. I haven't been able to trigger any codes since my original post. I used the car scanner app to warm the car up to 185F coolant temperature. Then I waited 1 hour and restarted the car. Coolant temperature was 105.8F. 5 hours later, the temperature was 95F. (Sorry, @Tombukt2, @mr_guy_mann, I didn't listen for the coolant T pumping/sampling exactly at 5h, so I can't be sure about the pump and T sensor).

    There's also been no coolant in the oil for about 600 miles.

    So that seems to confirm what confused @Danno5060 : the coolant in the oil that was reported by my mechanic seems to have miraculously cured itself (?) or else was never there in the first place. I'm sorry for the red herring! I just usually believe my mechanic.

    So it seems to suggest (1) CHS Tank is not holding heat as it should: bad insulation. or else (6) failed/ing CHS Tank Outlet T Sensor. (7) blocked hose or conduit between any of the above. (8) some combination of the above. I'll keep an eye on it.

    Thanks again.
     
    #41 Michael Evans, May 13, 2024
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    I don't know anything special about 5 hours.

    Really, the next morning when you ready the car up: the ECT and CHS temp sensors should read near ambient. The CHS pump should run for several seconds. You should see the ECT (& CHS) temps rise "a bunch" before the ICE starts.

    You can get a scantool like the Autel AP200 for $55 at amazon. It has all the prius specific data like CHS temp.

    If not you need to confirm: that the CHS pump actually works, that the temp sensors read correctly, that the coolant control valve works properly, that the coolant hoses are routed correctly.

    I would carefully drain some coolant from the tank the next morning to see if it was hot.

    Posted via the PriusChat mobile app.
     
    #42 mr_guy_mann, May 13, 2024
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