Oil leak in the back by the oil pan and starter.

[UmmScott]

Hey guys. Question for you all.

My yukon was a pretty low on oil today so i added oil and decided to leak check it.

Found that there is oil over the starter, the rear of the oil pan, and pretty much over the bottom of the transmission bell housing. I pulled the inspection cover off to look into where the flywheel and torque converter are.
Everything is dry inside there. No oil on the flywheel at all nor the converter, its all dry in there.
I do see the light blue/green edge of the rear main seal. Looks very slightly damp with oil but i see no trails or anything inside.

Anywhere else i should look? The oil pan was replaced by a contractor before i purchased the truck. Its got roughly 178kmiles on it.

Any other places i should check? It doesnt leave any spots in the driveway or parking spots. Just i would think that a rear main seal would leave the flywheel all wet with oil if it was leaking.

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[Danny3737]

Check the valve covers

 

[iamdub]

Could be an oil pan gasket leaking. Even if it was replaced along with the pan, it could've been done incorrectly or they didn't use sealant at the four required points.

Or, as Danny lead on, it could be coming from up higher- oil pressure sensor, valve covers, etc.

Clean it off (engine degreaser and/or brake cleaner), let it dry, then drive for a little while and check it for fresh leaks to find the source.

 

[mang213]

I would definitely check that oil pressure sensor and valve covers. Common issues that are easy to fix

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[OR VietVet]

Inspect back of intake while in there. Since you said back of oil pan I would asume the front seal is fine but would not hurt to inspect as well.

 

[sumo]

Also check the oil cooler block off plate. The gasket can be easily replaced

 

[drakon543]

another simple check is just to check the bolts on the oil pan. of they weren't tightened properly they could have backed out a bit and its causing a leak.

 

[iamdub]

So many possibilities. Gotta clean it off and watch for the fresh leaks.

 

[Bombsquad85]

Check the oil pressure sensor. I replaced mine about a year ago (maybe longer) and thought it was o. There tight. Well the other day I swapped out my O2 sensor and saw that the entire back of my engine was drenched in oil. Thought it was the pan or starter bolts at first.
Then I did my Knock Sensors and when I checked the oil sensor I saw that it was actually loose!. Apparently my 1 1/16 socket was too thick to fit in between the sensor and valley pan cover bolt so it didnt get it nice and tight. I can 100% see this being a common issue.

As you can se in the picture I had to remove the valley pan bolt to get the socket on snug

 

[89Suburban]

Could also be the valley pan gasket.

 

[mang213]

Oil cooler lines at the mating surface with the oil pan are known to fail as well. But that leak is very specific to a general area and won't spray the whole back of the block like the oil pressure sensor will

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