20 Sierra 6.2L rear main seal leak for the 4th time.

LilBean1982 · March 12, 2022

I’m new here so bare with me. I have a 2020 Sierra with the 6.2L. Back in November I was on the interstate and while passing a few vehicles my truck started smoking like crazy. I took the nearest exit and crawled beneath the truck and noticed engine oil was leaking from the rear main seal. At the time I had around 73,000 miles on the truck. I brought it to the dealership and they changed the seal which took them two weeks. The night I got the truck back I passed up a vehicle on a single lane highway and it happened again. So the next day I brought the truck back to the dealership again and they change the rear main seal in two days. Well this time it lasted about a week and it blew out again. So back to the dealership.

This go round they did more test to figure out what the cause of the problem was and Found out that #1,7,&8 cylinder rings were bad which was allowing blow by into the crank case and was blowing out the rear seal. After having the truck for one month they decided to put in a new engine. I forgot to mention during that time the modifications I had were K&N cool air intake, airaid throttlebody spacer, Flowmaster exhaust, and superchips flash pac handheld tuner.

After getting my truck back with the new engine everything was fine. I decided to gut out the cats and installed 02 sensor simulators to prevent the engine light from coming on. Well here we are 10,000 miles later and the rear seal has blown again. Same scenario of punching the gas to overtake a few vehicles on the expressway. I’m so frustrated. The 100,000 mile warranty on the new engine is now voided due to exhaust mods which I think is crazy. Can’t find anything online about others with the same issue. Has anyone here experienced or know of another situation like this? Any thoughts on what the cause could be. Thanks in advance.

Edited March 13, 2022 by LilBean1982
Spelling correction and typos.

redwngr · March 14, 2022

Should have been voided with the tuner.

LilBean1982 · March 14, 2022

15 hours ago, redwngr said:

Should have been voided with the tuner.

I removed it and installed the factory tune and they said nothing about it.

AirForceAngler · March 14, 2022

Here's my advice: Quit Eff'ing with the tune and the truck! Put cats back on it and leave it alone.

Jay P · March 14, 2022

You do know the ECM controls oil pressure & volume. It's possible your tune is the cause of the leak.

Jay

redwngr · March 14, 2022

17 minutes ago, LilBean1982 said:

I removed it and installed the factory tune and they said nothing about it.

That's kinda the point.

You make the truck do things gm didn't intend it to do and then expect them to pay for your screw up.

And because of the extra warranty work caused by you and others doing similar, GM's warranty costs are higher and we all get to pay more for our trucks.

I have absolutely zero issue with those that want to modify their trucks.

I do have an issue with expecting GM (and therefore the rest of the truck buyers) having to pay when it goes wrong.

Imho, if anyone is to supply a warranty for mods it should be those that supply them.

There is no way GM should be expected to pay for issues due to someone else's 'engineering' (or lack of engineering)

Edited March 14, 2022 by redwngr

pokismoki · March 14, 2022

usually a rear main seal blows out when the pcv and valve cover vents are plugged or not flowing enough air, a few guys caused this issue by installing catch cans incorrectly . if you have a catch can remove it and see if the problem goes away,

Edited March 15, 2022 by pokismoki

pokismoki · March 14, 2022

check for vac leaks using your short term and long term fuel trims, make sure the blown seal isnt causing fuel issues

SVG · March 14, 2022

Sounds to me like your seal blows when are passing somebody. Maybe drive in the slow lane??

Just kidding OP. Hope you can find out what's causing this.

Jeffnrivercity · March 14, 2022

I have blown 2 rear main seals..second one lasted 2 days...I also have a whipple and the canned carb tune...40k on truck and 20k on the whipple mod

Pretty sure i have ring problems too...contemplating my next step...

Lilbean1982, what did your cats look like when you gutted them, clogged at all?

LilBean1982 · March 14, 2022

10 minutes ago, Jeffnrivercity said:

I have blown 2 rear main seals..second one lasted 2 days...I also have a whipple and the canned carb tune...40k on truck and 20k on the whipple mod

Pretty sure i have ring problems too...contemplating my next step...

Lilbean1982, what did your cats look like when you gutted them, clogged at all?

The downstream O2 sensor on the driver’s side was throwing a code indicating that the corresponding cat was not working properly anymore. It appeared clogged somewhat and also discolored in some spots. The passenger side one never threw a code nor appear bad in any way. I’m considering upgrading the rings along with a few other engine components but would hate to spend all kinda money not knowing if there’s something causing the rings to go bad. I know I’m not the only person that has the flashpaq for the 6.2L but can’t find anything else online about similar issues.

LilBean1982 · March 14, 2022

5 hours ago, redwngr said:

That's kinda the point.

You make the truck do things gm didn't intend it to do and then expect them to pay for your screw up.

And because of the extra warranty work caused by you and others doing similar, GM's warranty costs are higher and we all get to pay more for our trucks.

I have absolutely zero issue with those that want to modify their trucks.

I do have an issue with expecting GM (and therefore the rest of the truck buyers) having to pay when it goes wrong.

Imho, if anyone is to supply a warranty for mods it should be those that supply them.

There is no way GM should be expected to pay for issues due to someone else's 'engineering' (or lack of engineering)

I didn’t state anything about expecting GM to pay for the repair. I myself know that the exhaust mod would void the warranty. Don’t know what post you read but thanks for your unneeded response.

LilBean1982 · March 14, 2022

5 hours ago, AirForceAngler said:

Here's my advice: Quit Eff'ing with the tune and the truck! Put cats back on it and leave it alone.

It’s my truck. I will do as I please. I’m not complaining about anything nor expecting GM to repair it. I simply came here to see if anyone else knew of similar problems along with the cause or possible fix. Thanks for your two cents anyways.

LilBean1982 · March 14, 2022

5 hours ago, pokismoki said:

usually a rear main seal blows out when the pcv and valve vover vents are plugged, a few guys caused this issue by installing catch cans incorrectly . if you have a catch can remove it and see if the problem goes away,

Thanks. I will look into this.