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You see a little oil where the case halves meet, but I put dye in my oil, used a UV light, and this seam glows bright green, while I didn't see anywhere else that lit up very much. It just seemed like that was oil sprayed off some moving part.

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I have been trying to track down oil and transmission leaks for a year or two. I needed to replace 3 quarts of oil and 3.5 quarts of ATF in 5,000 miles! I think that I saw some ATF on the exhaust, but just a few drops. Since I don't see that leak I have tried to focus on the oil. I keep cleaning the engine and trying to find the leak(s). The dye was all over the oil pan, but not above it.

A mechanic verified the oil pan gasket was leaking, so I replaced it, but the leak continued.

Another mechanic pointed out oil behind the valve cover leak, so I cleaned it, and didn't see new oil.

He immediately suggested that my rear main seal is leaking, which is possible, but as far as I can tell oil is dripping onto the transmission where the case halves meet and running down. Wouldn't a rear main seal leak from the transmission, not onto it?

My car had some recalls, so I took it in for that, and asked the dealership to find my leaks. The mechanic didn't notice any ATF, but said there was oil all over the bottom, and there wasn't Hondabond on the corners of the [Felpro] valve cover gasket, so obviously I need to replace that, and they will put Hondabond on the corners. There isn't oil below the gasket!

He sent me a video showing oil on the mating surface of the oil pan and all over the bottom of the car, but he said he couldn't see where the leak was, but it must be the lack of Hondabond on the corners of the valve cover gasket!

Someone mentioned the distributor seal.

Are there any other likely culprits?

I spent hours trying to research what could leak onto a transmission and just found results about transmission leaks, but nothing useful.

When I tried to figure out how to diagnose a rear main seal leak I just found ads from stop leak products.

From where do you think it is leaking? Thank you very much! Have a great day!

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  • I can't tell ... is the image from the top or the bottom? And this is an automatic transmission, right? Feb 9, 2023 at 17:24
  • This is the bottom of the automatic transmission.. A mechanic asked if there was oil pooling on top, but I left it at the dealer doing the recall repair. They needed to order parts and I needed to work.
    – Menlo Part
    Feb 9, 2023 at 18:33

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If the oil is at the mounting part between the transmission and the engine, and you're sure it's engine oil, about the only place it could be coming from is the rear main seal. There is an off chance it might be leaking from some other small passage at the back of the block, however, the high likely hood here is it's from the rear main. The only way you'd be able to tell is to pull it apart, but I'd give it a 95+% probability that's where you're getting the oil from considering what you've spelled out in your question.

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  • Thank you. It sounds like it is time to sell this car as-is.
    – Menlo Part
    Feb 9, 2023 at 19:17

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