Fluid on back of engine

Just had the oil changed in my 2013 Yukon 5.3. Guy that did it said there is fluid on the rear of the engine. He mentioned oil pan or rear seal. Any ideas? There is no fluid dripping onto the ground at all and it runs fine.

Crawl under and have a look. Take a pic or 2 and post if you're not sure. Degrease it afterwards and see if you can find a starting point possibly.

Common areas are: oil pan gasket, rear main seal (usually the housing gasket, not the seal itself), oil cooler blocknoff plate, or oil cooler lines.

If a leak is so slow, that it does not detectably drip, it's rust prevention ... for now -
but keep an eye on it - it's not gonna leak any slower as time goes by.

B-train said:

Crawl under and have a look. Take a pic or 2 and post if you're not sure. Degrease it afterwards and see if you can find a starting point possibly.

Common areas are: oil pan gasket, rear main seal (usually the housing gasket, not the seal itself), oil cooler blocknoff plate, or oil cooler lines.

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Right on, will get under there tomorrow. I got the oil changed earlier (miles wise) than usual as the vehicle sits for months on end up here Alaska until I get back up here. He stated that the oil was not low. Who knows. I do know even if it’s slow I would like to get it taken care of because when I do drive it, it’s 100’s of miles and remote. I assume each of the possible problems has varying degree of cost.

check oil cooler block-off plate or lines first and hope thats it! 2 bolts easy. 10mm head

the rest i don't like to think about, though they all seem inevitable...

"On rear of engine"? The transmission is "on" the rear of the engine. Something from above, intake or oil sender, could be leaking. Numerous items on the sides have been named. Right now you have seepage, or you would be seeing drops on ground. Time to clean and inspect and post pics.

mikez71 said:

check oil cooler block-off plate or lines first and hope thats it! 2 bolts easy. 10mm head

the rest i don't like to think about, though they all seem inevitable...

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^^^This. Both of mine started leaking from this in the past few years, and it looks just like a rear main seal leak except that inside the bellhousing was dry. One of mine has the block off plate just above the oil filter and the other has oil cooler lines there. The block off plate itself warps slightly over time and it wouldn’t even seal with a new gasket. I replaced the factory plate with one made by ICT Billet that has on o-ring style seal on my ‘07 and installed new oil cooler lines on my ‘12, which come with a new mounting plate and gasket. Problem solved in both cases.

OR VietVet said:

"On rear of engine"? The transmission is "on" the rear of the engine. Something from above, intake or oil sender, could be leaking. Numerous items on the sides have been named. Right now you have seepage, or you would be seeing drops on ground. Time to clean and inspect and post pics.

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I will get under there today with a light and take a look. I bought it two years ago and the transmission had just been replaced a month earlier. I was wondering if it was something residual from whatever went down with its replacement.