Empty Coolant P261B

Discussion in 'Gen 3 Prius Main Forum' started by antonioa, Dec 30, 2024.

  1. antonioa

    antonioa New Member

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    I recently cleaned my intake manifold and egr valve because of a cylinder misfire issue which ended up being spark plugs so those also got changed, when taking everything apart the coolant hose got pulled and drained my coolant closest to the radiator i’m getting the p261b code for a water pump issue but i think it may be the lack of coolant? i’m not sure and would possibly like any tips. thank you
     
  2. Brian1954

    Brian1954 Senior Member

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    What year is your Prius? How many miles on the engine? How long have you owned the car?

    Fill up the engine coolant and see if the trouble code clears or remains.
     
  3. antonioa

    antonioa New Member

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    It’s a 2010 with 198k on it, topped it up on coolant yesterday and lost the little bypass cap on the side just replaced it with a vacuum cap as i can’t find a replacement cap anywhere and now i am getting a high temperature coolant reading
     
  4. antonioa

    antonioa New Member

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    unsure of wether or not anything needs to be re pressurized or anything because when the coolant initially drained the hose that was released let out quite a bit of air
     
  5. Brian1954

    Brian1954 Senior Member

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    At 198k, I would replace the engine water pump with a Toyota OEM pump. Use new coolant when you install the new pump.

    How long have you owned the car?
     
  6. Mendel Leisk

    Mendel Leisk Witness Leader

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    Was there a misfire code, say P0XX, and if so what numerals in the X positions?

    How did you conclude the misfire was due to spark plugs? With those miles and misfire codes EGR cleaning is usually futile, head gasket will have failed. I’d check for coolant seeping into combustion chambers first, say boroscope inspection, preferably with coolant system pressurized to accelerate the leakage.

    then clean EGR system.
     
  7. antonioa

    antonioa New Member

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    Unsure of how long the car has been owned but i know its been owned for quite a while, I thought it might be a good idea to replace the water pump since the car was throwing up the code for a water pump issue, but for some reason the code has disappeared and been replaced with a coolant sensor code.
     
  8. antonioa

    antonioa New Member

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    Changing the sparkplugs was kind of the next most budget friendly step so thats what lead me to change those, but after changing it went from 2 cylinder misfires down to 1 and the code it currently has for the misfires is P0301
     
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  9. Brian1954

    Brian1954 Senior Member

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    The coolant sensor code P0117 means the engine has severely overheated. Based on the overheating and a P0301 cylinder #1 misfire, you could have a bad head gasket. It's time for proper head gasket diagnoses.
     
    #9 Brian1954, Jan 3, 2025 at 10:05 AM
    Last edited: Jan 3, 2025 at 8:42 PM
  10. antonioa

    antonioa New Member

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    I see, i changed out the sensor today because i thought it may have been that but how would i go about doing a head gasket diagnostic?
     
  11. Brian1954

    Brian1954 Senior Member

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    Use a borescope to inspect the cylinders while the engine coolant system is pressurized. Do a search in this forum, and you will find much information about what to look for while you use the borescope.
     
  12. antonioa

    antonioa New Member

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    okay thank you i’ll have to figure out how to pressurize it aswell
     
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