Oil found on Cylinder head

Discussion in 'Gen 3 Prius Technical Discussion' started by Cameron Walker, Sep 10, 2025 at 11:17 AM.

  1. Cameron Walker

    Cameron Walker Junior Member

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    To be fair, this one may be fault hahaha after 20 years of being my own mechanic i made the most rookie mistake. I overfilled my oil… Car was running like absolute garbage after the refill and spitting white smoke out of the back, I moved it into the driveway (where it almost died on me) so i could tear it apart to find a puddle of oil sitting on top of cylinder 1 and 4 with some light oil in 2 and 3, and eventually threw a p3190 code. I was able to get them all cleared of oil and just need to burn off the excess in the exhaust.. at least thats what im hoping for…

    What should i look for in other areas of the engine to make sure no major damage was done..
    Biggest fear is head gasket but im not afraid of taking that on. Should i swap valve cover gasket? Pcv valve? Piston rings?!?! Not sure how far down this rabbit hole i need to go.. anyone have experience with this?
     
  2. Brian1954

    Brian1954 Senior Member

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    How many quarts overfilled was it?
     
  3. Cameron Walker

    Cameron Walker Junior Member

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    At least 1.5 sadly. I filled it on a slope and then realized once i moved it. The car does have just over 200k miles on it, im wondering if this was the breaking point for it. Just completed a compression test.

    Cylinder 1: 190
    Cylinder 2: 170
    Cylinder 3: 180
    Cylinder 4: 190

    So it seems at least my piston rings seem to be holding on
     
  4. Cameron Walker

    Cameron Walker Junior Member

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    I also put it all back together today and fired up to try and burn the excess but its still pumping out a ton of smoke and died on me, so there is definitely still an issue
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    You did remove the excess oil out of the sump?

    Seems 1.5 qts extra would not be that bad but it's possible the pcv valve sucked oil into the intake manifold. Gen3 intakes usually have a pool of oil anyway from blowby and a poorly designed pcv location but you might have a half quart or more in there now.

    I would carefully remove the air intake box, maf cable and hoses and inspect via the throttle body. Suck out what you can.

    Then try to burn the residual off. The plugs could be soaked but once you remove the root cause they should burn off as well.

    Hopefully it did not hydrolock a piston. But there is no magic solution if that happened so proceed with clearing the intake.
     
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  6. Cameron Walker

    Cameron Walker Junior Member

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    I’ll take a look! Ill have to remove all of it anyway to replace the head gasket if thats what i need. I cleaned the plugs before running it again this morning and after my short trip they were coated again.

    The pistons are still free flowing and not locked up at all.

    I will send an update tomorrow!
     
  7. ASRDogman

    ASRDogman Senior Member

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    You "SHOULD" drain the oil in a clean pan. Then, after reinstalling the drain plug, fill
    the engine with 4 qts of oil. Start the engine and let it run until it stops.
    Wait a minute then check the oil level. Do not add more than half a qt at a time if you need to add any.