2005 Yukon Xl With A 5.3 Liter V8 Engine (l59) Oil Leak

yukonxl2005 · January 10, 2008

I have a 2005 Yukon XL with a 5.3 Liter V8 engine (L59), at about 5,000 miles the engine developed a small oil leak at the engine rear main seal, see attached photo. The dealer replaced the rear main seal and the valve cover gaskets.

However, the leak has continued for the last year and a half (25,000 miles). The leak is small enough so no oil is found on the floor but as shown in the pictures, the oil covers the bottom of the cast aluminum oil pan. The area is cleaned but always returns as shown in picture, I have confirmed the leak is not coming from any part of the valve covers or the oil drain plug.

I found information about Bulletin #05-06-01-34E (Engine Oil Leak at Rear Cover Assembly Area), however this bulletin only applies to the 2007 Yukon XL. Is there a similar bulletin for the 2005 Yukon XL? What is leaking?

Yukon_XL_Pic1.pdf

grosss · January 6, 2009

Trey,

From what you said, I should be able to see the oil from the center of the flywheel while the engine is off right? :-D Should the engine be warmed up before I look?

grosss · January 4, 2009

C& A,

I was just informed by the shop that did my oil change (because I took it back after noticing the filter was covered in oil) that the rear main seal is leaking. From you description below I think it might be the oil pan leak you are talking about. The tech said that the oil was getting onto the flywheel and spraying everywhere, which is why it looked so bad. I have the autotrac 4x4, any idea if I can change the oil pan seals without having to remove the tranny? I didn't really take a look at that when they had it on the hoist since I figured they were probably right about the main seal.

My 02 ended up being the OP gasket as well. The oil pan is structual and actually has presurized oil passing through 2 ports into and out of the filter housing. These ports are about the size of a nickel and the op gasket has a o ring style seal built in around these ports. When they leak, they typically leak to the inside of the bell housing and the flywheel pulls the oil into it causing oil to leak out of the "weep hole" at the bottom of the bell housing. This will give the appearance of the rear main seal leaking when it really is not. My guess is there have been many rear main seals replaced in 5.3s that did not need replacing at all.

C & A s Dad · January 10, 2008

I took a look at the pic.

I have 2 suggestions.

1) Pop out the metal inspection plug and see if you can feel excessive oil inside the cover. If it is the rear main, there should be a good deal of oil inside this cover. If it is dry in there, you know your leak is coming from another source. The cover is about the size of the bottom of a coke can and has 3 spring loaded catches to hold it in. It is near your drain plug.

2) In the pic it does not appear to be the source, but make sure it is not leaking around the block off plate for the oil cooler lines. This is the piece just above your filter and is about 3" long with 2 bolts holding it to the block. I found a little oil around mine and discovered it was not tight at all and I had to snug it up a little. I have not seen any more oil since then.

You did not ask and I should not say anything, but if that is a Fram filter, you have to know they are on the low end of the filter food chain. Don't want to start a "which filter is best war" here, but this is the general opinion of Fram oil filters especially from those of us who have seen them disected.

C & A s Dad · January 6, 2009

You are right. If it is the rear main seal, the oil would be coming from the center of the flywheel and spinning outward.

This is what made me question the GM Tech that was looking at mine. I had oil in the bell housing and around the outer edges of the flywheel but very little oil on the surface area of the flywheel near the shaft. They added dye to see if that would help. After they could not determine exactly where it was coming from, I bouht a UV light and began looking. I also did some research on here and another forum and finally found where someone had uncovered the oil pan gasket leak.

I printed off what I found, took the truck back and showed the info and the oil/dye that I could see and they agreed. He pulled the pan, replaced the gasket and all was well. She is dry as a powder house under there now.

I do not think you need to have it warm. If it is leaking the oil will be there warm or not.

C & A s Dad · January 5, 2009

Stu,

On a 2wd I know the trans does not have to come out but I am not sure on a 4 x 4.

This leak could certainly be a rear main but my bet is it is your oil pan like mine was. There are many rear main seals needlessly replaced on these engines due to the leak being mis-diagnosed.

If it is the rear main seal, you should be able to remove the inspection plug and literally see oil coming from the center of the flywheel area. It is very difficult to diagnose because the suction motion of the spinning flywheel will pull the oil from the leaking pan into the bell housing giving the appearance of a rear main leaking.

Let me know what you find.

VMax2007 · January 5, 2009

Stu,

On a 2wd I know the trans does not have to come out but I am not sure on a 4 x 4.

This leak could certainly be a rear main but my bet is it is your oil pan like mine was. There are many rear main seals needlessly replaced on these engines due to the leak being mis-diagnosed.

If it is the rear main seal, you should be able to remove the inspection plug and literally see oil coming from the center of the flywheel area. It is very difficult to diagnose because the suction motion of the spinning flywheel will pull the oil from the leaking pan into the bell housing giving the appearance of a rear main leaking.

Let me know what you find.

Hey Trey,

I liked the "Be American, Buy American" quote in your sig. I hope you don't mind me using it too.

C & A s Dad · May 14, 2008

My 02 ended up being the OP gasket as well. The oil pan is structual and actually has presurized oil passing through 2 ports into and out of the filter housing. These ports are about the size of a nickel and the op gasket has a o ring style seal built in around these ports. When they leak, they typically leak to the inside of the bell housing and the flywheel pulls the oil into it causing oil to leak out of the "weep hole" at the bottom of the bell housing. This will give the appearance of the rear main seal leaking when it really is not. My guess is there have been many rear main seals replaced in 5.3s that did not need replacing at all.

I am assuming it took so long to repair yours due to it being a 4 x4. It took them just an hour or so to replace my gasket and to date, the leak has not come back. If I had known this at the time of your first post, I would have shared all of this with you however, I did not find it out until later.

BTW, I ended up self diagnosing mine using dye and a uv light. The Dealership was nice about it but after 2 trips in they said they could not see where the oil was coming from. I did some research on a few forums, bought me a UV light and I found it. They listened to me and read the info I had gathered when I took it back the third time and discovered that I was right.

C & A s Dad · January 5, 2009

No problem Jeff. I do my best to live by this but sometimes it is difficult. Not when buying a vehicle of course, this comes very easy for me because I would rather have a picture of a GM Truck on my wall than have a Toyoyo in my garage.

yukonxl2005 · May 13, 2008

I took the Yukon XL in to get fixed, it turned out that the leak was coming from the oil pan gasket. The oil pan gasket goes up into the bellhousing, it took the dealler a week to disassemble and reassemble, everything, I look and the oil pan, it seems the 5.3 oil pan is a major part of the engine block.

Oil.

I took a look at the pic.

I have 2 suggestions.

1) Pop out the metal inspection plug and see if you can feel excessive oil inside the cover. If it is the rear main, there should be a good deal of oil inside this cover. If it is dry in there, you know your leak is coming from another source. The cover is about the size of the bottom of a coke can and has 3 spring loaded catches to hold it in. It is near your drain plug.

2) In the pic it does not appear to be the source, but make sure it is not leaking around the block off plate for the oil cooler lines. This is the piece just above your filter and is about 3" long with 2 bolts holding it to the block. I found a little oil around mine and discovered it was not tight at all and I had to snug it up a little. I have not seen any more oil since then.

You did not ask and I should not say anything, but if that is a Fram filter, you have to know they are on the low end of the filter food chain. Don't want to start a "which filter is best war" here, but this is the general opinion of Fram oil filters especially from those of us who have seen them disected.