Oil leak front engine cover (not oil sensor)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by amarino, Jan 24, 2026.

  1. amarino

    amarino Active Member

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    Doing my oil change today I noticed a leak that was coming from above where the oil pressure sensor is. I know the oil pressure sensor is a common leak and was already planning to replace it, but this seems to be coming from higher up on the front cover. It went all the way down to the oil filter housing / oil pan. It looks to be coming from that brown block off plate next to the exhaust manifold. For now I just cleaned everything with brake clean and I'll check again at my next oil change, unless I notice it on the floor of the garage first.

    Anyone dealt with this before?

    PXL_20260124_005137134.jpg PXL_20260124_004937561.jpg PXL_20260124_004909920.jpg PXL_20260124_004734176.jpg
     
    #1 amarino, Jan 24, 2026
  2. PriusCamper

    PriusCamper Senior Member

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    Yes... Cleaning everything and re-inspecting later is the correct way to do it! I'm not seeing anything to be alarmed about. Looks like a typical engine that may have had some oil spilled during an oil change/adding oil. What stage of engine oil loss are you at? As in how many miles per quart lost? Also, how many miles on the odometer?
     
    #2 PriusCamper, Jan 24, 2026
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  3. PriusTech

    PriusTech Active Member

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    Pretty common. Right at the junction of three parts, the head, the block, and the front cover, there's no gasket, they use sealer. The factory made a little recessed space on the front cover to hold more sealant. You can see that junction in your pic. The sealant degrades over time and leaks. Did a bunch of these at the dealer, it's not cheap. I think it's because the machining process on the aluminum leaves it too polished and the sealer doesn't have a rough enough surface to grip and it slips out.

    If you are going to DIY scuff all the sealing surfaces with red scotch pad and wipe with brake clean. Get a good grey permatex silicone, or toyota brand sealer and read the directions. Apply and bolt together only finger tight. Do not fully tighten right away. Let it dry for an hour and then tighten. This leaves a thicker layer of silicone. If you tighten right away it's thin and flimsy.

    IMG_20260124_154332641_2.jpg
     
    #3 PriusTech, Jan 24, 2026
    Last edited: Jan 24, 2026
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  4. amarino

    amarino Active Member

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    At around 109,000 miles on the car. Have not noticed any oil loss so not adding any in-between changes which is about every 6 months / 6k miles or so. I also did an EGR/intake cleaning at around 60k or 70k miles.


    Thank you for the awesome picture. I'm assuming it's not cheap because the entire front cover needs to come off. I'll save that trouble for when the head gasket goes or something more involved.
     
    #4 amarino, Jan 24, 2026
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  5. rjparker

    rjparker Tu Humilde Sirviente

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    Timing Chain Cover leak vertical.jpeg
    Timing chain cover leaks are common. Not all are seeps.
     
    #5 rjparker, Jan 25, 2026 at 12:42 AM
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