2012 Yukon Denali XL with 6L80 and 6.2L. Oil leak at rear of engine?

[testdepth]

I know the leak is not from the oil pressure sensor, the valve cover gaskets or the oil cooler gasket. All have been replaced less than 6 months ago and all have been inspected showing no leaking.

As far as I know that leaves either the oil pan gasket, rear main seal or the rear cover gasket. How do you determine where the leak is actually from as the repair is different for both?

 

[SpareParts]

Check that oil cooler gasket again. They have a habit of leaking after the gasket has been replaced.

 

[mikez71]

I think that is a tough one to determine..
Have heard of people looking through the bellhousing inspection cover, and using dye, and it's still hard to tell.

Seems like the rear cover leaks more often than the actual rear main seal.
I'm planning to do oilpan first.. but am not getting my hopes up in case it's the rear cover..

 

[testdepth]

Check that oil cooler gasket again. They have a habit of leaking after the gasket has been replaced.

I looked again and it's bone dry. I wish it were that simple lol.

 

[testdepth]

I think that is a tough one to determine..
Have heard of people looking through the bellhousing inspection cover, and using dye, and it's still hard to tell.

Seems like the rear cover leaks more often than the actual rear main seal.
I'm planning to do oilpan first.. but am not getting my hopes up in case it's the rear cover..

I have also read the rear cover gasket leaks more than the rear seal but the work is the same. Transmission has to come out to replace either. If you take it to a shop that's about $1200 to replace a $40 part.

I'm going to try this stuff first "AT 205". I have seen lots of positive videos using it and a very long thorough test that showed it does in fact soften the old seals and they return to the original size which just may seal it back up. For $20 I'll try it and cross my fingers. Pulling the transmission in my driveway in this Denali is about as much fun as pulling the fuel tank.

 

[Joseph Garcia]

I have also read the rear cover gasket leaks more than the rear seal but the work is the same. Transmission has to come out to replace either. If you take it to a shop that's about $1200 to replace a $40 part.

I'm going to try this stuff first "AT 205". I have seen lots of positive videos using it and a very long thorough test that showed it does in fact soften the old seals and they return to the original size which just may seal it back up. For $20 I'll try it and cross my fingers. Pulling the transmission in my driveway in this Denali is about as much fun as pulling the fuel tank.

Before you use the AT 205 product, let's hear from @OR VietVet , as he recently referred to some product of pellets that work real well, and is used by GM.

 

[OR VietVet]

The pellets stuff is the GM "pills" that GM uses for the cooling system.

AT 205 and other additives, IMO are snake oil. Nothing works better than the part/seal/gasket replacement and having a completely clean and dry sealing surface. If I am installing any part that has a rubber seal in place already, I use a very thin smear of "Blue Goo" on the surface of the seal to allow for seal movement during install and tensioning and it actually helps the sealing process as well. Not a gob of it, just a very light smear. Use GM parts where available.

I am completely convinced and know that some of the biggest reasons that there are oil leaks, is that way too many times, the vehicle owner pushes the oil change intervals because they believe some of the crap info that the oil companies use when selling. Use a good quality filter and IMO, change the "synthetic oil" every 4 months or 4k miles. If you use the dash cluster oil change reminder, good luck to you. If you believe the oil companies and think it is ok to go a tear or crazy miles in between oil changes, again, good luck to you.

The oil is the "blood of the engine". Oil changes are cheap compared to leak repairs and you can always know the price ahead of time.

Too many times I see people here and at other forums, BRAG about oil change intervals. IMO, they are just kidding themselves.

 

[rdezs]

And often overlooked source is the VLOM plate, or valley cover plate gasket if you have AFM deleted.

Almost every VLOM plate I have removed has had at least four or five bolts loose.... Resulting in the leak at the rear of the engine up top.

I've never actually ran across the rear cover leaking. Usually it's been either the oil cooler line block, rear corners of the oil pan gasket or the rear main with a very slight leak, not enough to really drip, but it sure makes a mess

 

[Marky Dissod]

AT 205 and other additives, IMO are snake oil.

There is a short list of additives that can materially prove their superiority over 'snake oil', and most are already in the motor oil,
and balanced against each other by the tribologists responsible before you changed your oil.
If you'd like to add to that list, do a used oil analysis, show your work.

There is an important difference between
"it's been around for over 50 years, so it must be good for something"
vs
"it's been around for over 50 years 'cause it's harmless; harmless is NOT 'good for something', it's ineffective, except you paid money for nothing instead of something"

I am completely convinced ... that some of the biggest reasons that there are oil leaks, is that way too many times, the vehicle owner pushes the oil change intervals
because they believe some of the crap info that the oil companies use when selling.

Changing motor oil early will certainly keep an engine alive longer than changing motor oil late. Motor oil is cheaper than an engine, and the latter are seldom on sale.

If you use the dash cluster oil change reminder, good luck to you.

You can better this luck by changing oil @ 20% / 25% / 33% / 50% depending on your recent fuel mileage.
The better your fuel mileage, the further you can go between oil changes.
'but I change my oil every 3000 miles.'
3000 highway miles @ an avg speed of over 45MpH, is NOT the same, as 3000 stop'n'go city/neighborhood miles @ an avg speed of under 20MpH,
and no NYC cabbie changes their oil AFTER the OLM gets under 20% - some change as soon as 50%.

 

[SpareParts]

Do the additives work on PTFE seals?

 

[Marky Dissod]

Do the additives work on PTFE seals?

Sorry, don't know the answer to this. Likely better to find the answer to
"WHICH additives work WITH PTFE seals?" (LubeGard looks promising ...)

 

[SpareParts]

Reason im asking is LS engines have PTFE seals. I would think most additives would not have an effect on them.

 

[testdepth]

The way I look at is it will either stop the leaking or it won't. If it doesn't then I still have to fix it but for $20 it's worth the try.

 

[Marky Dissod]

Never in my wildest dreams have I ever considered 'stop leak' products similar to anything like

https://www.schaefferoil.com/documents/37-132-td.pdf

if only because I'd never pour any of those 'stop leak' products into an engine.

 

[Goldwing2000]

+1 on the VLOM/valley plate. Very common to leak and often disguised as a leak something lower on the engine.

 

[West 1]

The engine has many parts that lubricate through small holes, inserting stop leak into your oil system can plug holes needed to lubricate. I have never been a fan of oil system stop leaks.

In the past year I did the rear main seal on my 2003 and on the 2008 Denali 6.2L. It is great to finally have no oil leaks.

 

[TahoeRestore]

I went through this recently. See my post - https://www.tahoeyukonforum.com/thr...inding-my-oil-leak.157600/page-2#post-2041348