Oil leak: cleaning and diagnosis help needed

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Arkay, May 26, 2026 at 2:47 AM.

  1. Arkay

    Arkay Junior Member

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    2014 Plugin Prius:
    While changing the oil today, I noticed that the area was covered in oil. There were no oil drips on the floor so it is not "yet" a major problem.
    The oil leak was from above the pan and filter area, BUT below the belt.

    I think it is the oil pressure switch, but I have an almost 100% track record of my first guess being wrong :) .

    Here are a few questions:

    1. How can I clean that area? What is the easiest way to clean it?
    I was thinking of spraying a simple degreaser in that area and then washing it off. Anything particularly wrong with that approach? Apart from the engine needing to be cold!!!

    2. How do I diagnose the problem? I was thinking of using an engine UV dye + black light. Do I also need a borescope?

    3. Assuming it is the oil pressure switch, how do I get to it? The manual says I can get to it by removing the front right wheel.

    4. Could it be timing chain cover seepage?

    Thank you!!!
     
    #1 Arkay, May 26, 2026 at 2:47 AM
  2. ASRDogman

    ASRDogman Senior Member

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    "...but I have an almost 100% track record of my first guess being wrong"
    Even a broken clock is correct twice a day!

    There are no oil drips because there is a pan under the engine.
    Gunk the engine, then hose it off. Drive the car making sure the engine runs for 10 minutes or so
    to dry it off. Then check from the top down.

    Valve cover gasket, oil pressure switch, timing chain cover or common areas for oil leaks.
    What belt are you talking about?
    It is possible the oil filter housing wasn't tightened enough, or the "O" ring was installed in the wrong
    slot on the filter housing, and air is blowing the oil everywhere.

    Cleaning the area completely, then checking often is the only way to find the leak.
     
    #2 ASRDogman, May 26, 2026 at 7:47 AM
    Arkay and Brian1954 like this.
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I’d spray brake cleaner, wipe with a rag.
     
    #3 Mendel Leisk, May 26, 2026 at 9:39 AM
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  4. Arkay

    Arkay Junior Member

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    > It is possible the oil filter housing wasn't tightened enough, or the "O" ring was installed in the wrong... :)
    Noooo, I am obviously perfect and never made any mistakes... Frankly speaking, that seems much more likely than Toyota making a defective part.

    I'll start with gunk. For any specific areas that didn't get cleaned, I can use brake cleaner while working on them.
     
    #4 Arkay, May 26, 2026 at 11:39 AM
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