Oil Leak - 2015 GMC Yukon

[Jake 2015 GMC Yuk]

I have a 2015 Yukon with the 5.3 and 6L80 transmission and 150K miles. Oil is dripping from the starter as well as the other side where the bell housing meets the engine. The place where the oil cooler lines attached was dry and so was the fly wheel (looking through the access cover) so i don't think it is the rear main seal. I removed the upper oil pan (GM calls it the oil pan assembly) which involved removing the front differential and the electric power steering arm. I also removed the starter to see if there was oil coming from the sensor above the starter but that was clean. The upper oil pan does not use a gasket for 2015's although older models do. I paid a lot for dealer RTV and also bought the 3 black O-rings from the dealership - those go into the upper oil pan before you replace it. Oil was coming from all four corners of the bottom of the engine block. As long as i was under there, I replaced the oil cooler lines (took 1 week from GMPartsGiant $70 including shipping) and the transmission cooler lines (Napa $120), transmission filter and gasket. For what its worth, removing the transmission pan was much easier in my example and didn't require levering down the exhaust like you see in a lot of videos.

Bolted it back together and it still leaks, although it leaks a little less, still drips down both sides where the transmission meets the engine. I removed the intake manifold but it is very difficult to see if the oil is coming from the valley pan (at the back of the engine) or from the head gaskets. It seems more likely that the valley pan is the issue because if the head gaskets were bad, they would BOTH need to leak to explain why oil comes down both sides of the engine.

I've tried the die, mirrors, pictures, etc. I'm reluctant to do the valley pan without confirming first where the oil is coming from. Does anyone have any suggestions? Or experience replacing the valley pan gasket? Is a valley pan gasket a common issue in these models?

Thank you.

Update 5/6/2024

I am ordering the parts to do the Valley Pan. I know i'll need to remove the High-pressure fuel pump and those disposable fuel lines that sit under the air intake manifold. But do you need to take the fuel rails off to get the valley pan off? Also, if i DO take the fuel rails off, should i replace the injectors while i'm at it? Thanks for the answers so far!

 

[Bigkevschopshop]

Well, you may try to look and see if you have any residue on top of the trans bell housing. That will help determine the leak area. From what you are saying, I wonder if the oil pressure sensor is going bad, I remember the old ones were right behind the intake on the block. Maybe worth looking into. The pans on these are pretty fool proof and rarely leak,
but I do know the VLOM gaskets and valley cover have been found to be loose and leak.

Just some food for thought!

Welcome to the Fray man!

 

[Jake 2015 GMC Yuk]

Well, you may try to look and see if you have any residue on top of the trans bell housing. That will help determine the leak area. From what you are saying, I wonder if the oil pressure sensor is going bad, I remember the old ones were right behind the intake on the block. Maybe worth looking into. The pans on these are pretty fool proof and rarely leak,
but I do know the VLOM gaskets and valley cover have been found to be loose and leak.

Just some food for thought!

Welcome to the Fray man!

Thanks for the response. i have lots of residue on top of the transmission bell housing, which makes me think it is the VLOM/valley cover thats leaking.

Around 2015, they put the high-pressure fuel pump on top of the Valley cover in the back of the engine near the firewall. That meant they had to move the oil pressure sensor to the front. It would be easy to replace and i might do it, but I can see that's not where the oil is leaking from.

Other suggestions are welcome.

 

[Bigkevschopshop]

Thanks for the response. i have lots of residue on top of the transmission bell housing, which makes me think it is the VLOM/valley cover thats leaking.

Around 2015, they put the high-pressure fuel pump on top of the Valley cover in the back of the engine near the firewall. That meant they had to move the oil pressure sensor to the front. It would be easy to replace and i might do it, but I can see that's not where the oil is leaking from.

Other suggestions are welcome.

If ya pull the intake, take a rag and run it right where the valley pan meets the block and if it comes up wet, then you found it.

 

[91RS]

It’s almost always the oil pan. It could be the rear main but I’ve only seen a few so far. Are you sure you cleaned it properly?

 

[Jake 2015 GMC Yuk]

It’s almost always the oil pan. It could be the rear main but I’ve only seen a few so far. Are you sure you cleaned it proper

Hi and thanks. When you say it is almost always the oil pa

It’s almost always the oil pan. It could be the rear main but I’ve only seen a few so far. Are you sure you cleaned it properly?

Do you mean 'it's almost always the Valley Pan? I already replaced the upper oil pan (beneath the vehicle) so i know that's not it.

 

[91RS]

No, I mean it’s almost always the oil pan. Are you sure you cleaned it properly? Are you sure you didn’t scrape any off putting the pan back up? It’s very easy to do, especially on the oil pump.

 

[Jake 2015 GMC Yuk]

Just to close the loop on this thread...

2015 GMC Yukon with the 5.3 Liter

I wound up replacing the valley pan gasket (sometimes called the Valve Lifter Oil Manifold or VLOM gasket), which fixed the leak. I was never really certain the valley pan gasket was the culprit until I had it bolted back together and ran it for a week or so.

If oil is coming down both sides of the bell housing (like it was in my case), then the valley pan is a good possibility. If only one side, then probably not.

Removing the valley pan:
1) pulling off the air intake is a pain (like you will see in other posts) because the electrical connectors attach to the air intake cover, which is frustrating. Watch youtube videos before you do this. make sure to tape off the air intake holes right away when the air intake (finally) comes off.
2) There are two fuel lines that are one-time-use. So have those two new lines purchased before getting started. Some videos suggest you de-pressurize the fuel system first but i didn't worry about that. I just let it sit over night and then used lots of rags to catch the gas.
3) the most-challenging step is removing the two fuel rails that sit above the valley pan. Watch videos and pay close attention to the pry bars used and angles of the pry bars. Once the front of each fuel rail pops out a little, pry evenly at three points (front, middle and back). Avoid the temptation to pry from the front only or the fuel rail will bend. I bent one of mine a little but was able to re-use both of them, luckily. Make sure to clean the injector holes and vacuum them out. Then cover them so nothing gets in there.
4) While i was in there, i replaced the injectors... There are little boots that some videos show are added to the new injectors (but didn't come with the new injectors). They are about the size of a quarter and seat an inch or two from the tip of each injector. There were no boots on the old injectors. I decided to add the boots and wasn't sure if that was right, but it worked well so that is what i'd recommend for my engine. I had to buy an injector-rebuild kit to get the boots and discarded the rest.
5) the valley pan comes off fairly easily once the fuel rails are out of there. Plan for 1.5 hours cleaning off oil residue. The high-pressure fuel pump sits on top of the valley pan and those 2 bolts go through the fuel pump, through the valley pan and into the engine (at the back). In order to put the fuel pump back in (when finished), you need to use a little tool to make sure the camshaft lobe is at its lowest point at the fuel pump. So i bought that $15 tool and hand-cranked the engine until the tool seated all the way down inside the fuel pump hole. I put a little extra RTV at the back of the valley pan gasket because that was where it previously leaked.

I'm not a mechanic. This was at the limit of my capability. I felt fortunate not to screw something up. Good luck!