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Oil Pressure Warning Light, Cold Weather, and Contaminated Oil

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Fractal20, Feb 28, 2023.

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  1. mr_guy_mann

    mr_guy_mann Senior Member

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    To my eye, the "coffee with cream" appearance of the old oil is typical of a fair amount of water/coolant contamination.

    Unless someone straight dumped water into the crankcase, the only explanation I have is some type of internal coolant leak.

    PCV problems can result in some emulsion "spooge" inside the fill cap, but not that much (& it would leak oil out of every seal and gasket).

    Posted via the PriusChat mobile app.
     
    #21 mr_guy_mann, Mar 21, 2023
  2. Fractal20

    Fractal20 Junior Member

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    I had edited my last post to include some details from the oil shop after you posted this reply. So the oil shop also said that after doing the oil change, it was overfilled yet again and they speculated that there was something taking up some volume, maybe ice. I'm assuming you would say that seems really unlikely, again unless someone straight dumped water into the crankcase? Again, it has been a very cold winter and I've only taken very short trips, like 10 blocks, all winter. So the car has been staying cold. But it still seems crazy for that much moisture to build up. If they really were careful in putting in the right amount and it was still overfilled, any idea what it could be?

    One more thing, does the oil on the dipstick post oil change seem like what you would expect? I thought it would be clearer. Again, just wondering if there is still lingering contamination in the oil.
     
    #22 Fractal20, Mar 21, 2023
  3. broski

    broski Junior Member

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    At least in my experience, draining the whole sump never seems to work for me. I routinely remove significantly less oil from the car than expected and add less than expected. Maybe closer to 3 quarts for an oil change even after tipping the car in the direction of the oil drain. Oil levels are fine, never had a CEL. It doesn't surprise me too much if you are over full if they just added 4 quarts without checking the dipstick on the way.

    If you truly had significant coolant in the oil you'd see milkshake. It looks clean enough to me (from here). Sounds like you need a Nissan Leaf or something more tolerant of your duty cycle.
     
    #23 broski, Mar 23, 2023
  4. dolj

    dolj Senior Member

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    It must be the way you're holding your head, I pretty much can drain out all the old oil and add back 3.9 qts. The level on the dipstick is always right around the top dimple (F mark) after priming the oil filter.
     
    #24 dolj, Mar 23, 2023
  5. broski

    broski Junior Member

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    Hmm. I'll try a bit harder this winter when I do my annual. 6000 miles to go
     
    #25 broski, Mar 23, 2023
  6. Fractal20

    Fractal20 Junior Member

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    An update: even though it seems far fetched that there is frozen moisture in the oil, I found a shop that was okay with living the car overnight inside, to thaw an potential frozen moisture, and then change the oil. I just picked the car up, and the oil looks good on the dipstick and 3.9 quarts filled it up as expected and it wasn't high on the dipstick like before.

    This makes me hope that somehow it was moisture in the oil rather than coolant, and that the head gasket is okay. But there still just doesn't seem like any feasible explanation of how the moisture got in there... my plan is just to drive it normally, check the oil and coolant often and see what happens.

    One thing I would like to double check is that there is a separate coolant system for the hybrid system rather than the gas engine. The coolant is not low in the radiator or the plastic coolant (over flow?) container right near the radiator. However, the plastic coolant container near the hybrid system, is a little low. If that coolant is low, is there any way that could get to the engine oil? I am wondering, because if not, none of the relevant coolant being low also seems to suggest it isn't coolant that was getting into the oil, especially enough to make it a quart over filled (and coolant wouldn't freeze, so it wouldn't explain something frozen taking up volume in the oil).
     
    #26 Fractal20, Mar 28, 2023
  7. Aegean

    Aegean Active Member

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    I do not see a way for the inverter coolant to end up in engine oil. It is a separate system for the inverter coolant passages with a reservoir, electric pump, a few rubber hoses, an air bleeding screw and finally the radiator portion. Nothing in the vicinity of the oil circulating system within the engine.
     
    #27 Aegean, Mar 28, 2023
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