What's on the back of engine, above oil pan? (Wet!)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by MrPete, Jul 19, 2025 at 1:07 PM.

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  1. MrPete

    MrPete Active Member

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    @PriusCamper your wish came true, unfortunately. ;)

    I'm suddenly seeing a pool of wet on the garage floor after each of the last couple of drives. Not oily. No real smell.

    I need to find what this is and solve it. We leave on a 4000 mile driving trip in one week.

    My main questions:
    • what are the (wet) bolts/devices on the back-right side of the engine, above the oil pan, and below-right of exhaust???
    • Could the black bolt in photos be loose?! (I've not attempted to change anything.)

    Jacked up car. Looking at the back side of the engine I see some wet components, particularly a black bolt, and another wet one above it that's hard to see.

    In the photos, "down" is toward the front of the car. I am lying beneath the oil pan, whose attachment bolts are visible in the final photo.

    The black bolt "under" the metal plate (and clip for some wire) was quite wet. A lighter bolt above it was dirty/wet. Then in the first two photos you can see a black bolt or cap or ??? that's also glossy/wet.

    I'll search for appropriate engine diagrams...

    THANK YOU! What an amazing community :)

    20250719_104930.jpg 20250719_105011.jpg 20250719_105059.jpg 20250719_105111.jpg
     
  2. NutzAboutBolts

    NutzAboutBolts Senior Member

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    It’s probably your timing chain tensioner gasket that is leaking from the top, it’s a common leak on that gasket. Mine was leaking too and I changed it when I did the head gasket.
     
  3. MrPete

    MrPete Active Member

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    Hybrid Pitstop replaced my entire engine (with a Gold 2015 rebuilt from ground up) only 30k miles ago.

    Is that a likely gasket leak so quickly?
     
  4. ChapmanF

    ChapmanF Senior Member

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    I saw that black-painted block, and wondered about that.
     
  5. NutzAboutBolts

    NutzAboutBolts Senior Member

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    looking at the first picture, it looks wet underneath the timing chain tensioner.
     
  6. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Is that black looking bolt suppose to be where the oil pressure sensor is at? I’ve never seen that type of black bolt before.
     
  7. MrPete

    MrPete Active Member

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    Good question. And THANK YOU for digging in with me on this!

    Here's a new picture from the side w/ the right front wheel off.
    100% of the wettish area is around the two connectors and the black bolt (which is behind (left of) and a bit below the upper connector.. Above these, it's dry dry dry.

    I do not know if this helps w/ identification: I notice that the upper connector is at right angle to the back of the engine. The lower one is tipped by 10-20 degrees or something like that.

    20250719_204805.jpg

    I am also wondering... could this simply be condensation from the A/C unit? Doesn't really sound right to me... grasping at straws I admit!
     
  8. NutzAboutBolts

    NutzAboutBolts Senior Member

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    from the looks of it, I’m not sure what that black bolt is since you have the oil pressure sensor and the crank position sensor there. I’d definitely call the dealership to see if they can see what that part is because it’s not on my 3rd gen Prius engine.

    and the ac condensation line is below with a hose that goes down on the passenger side seat. It wouldn’t be on the engine like that black bolt.
     

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