Another 6.2 failure

[Johncunningham]

All

I posted this a few weeks ago in an another thread. Thought I would start a thread to post follow up.

Initial event 6/27/24.


2023. Tahoe Premier. 6.2. 22k miles. Driving yesterday afternoon 65mph ish. Screen goes black. Engine dead. Coasted to a stop. Dipstick looked fine. When we pulled the oil fill cap, an actual puff of Smoke came out. Had it towed to the nearest dealer. Got to google the transmission disconnect nonsense with the driver on the side of the road to get it there.

Of course we were 300 miles from home. They had a diagnosis in 5 minutes. Thrust bearing failure. Another word for Crankshaft bearing?

In any event I’m waiting to hear that the warranty claim is approved.

Also, worth repeating from upthread. It was completely free of drama. One moment cruising. Next moment dead. No shimmy. No shake. No crunch. No shudder. No loss of power. No smoke. No steam. No sound. Just dead…


Now for the update.

Anyhow, it took them a few days to get GM approval. Engine shipped 7/5. Work finished 7/17. I picked it up today. Drove it home 300 miles… Ran like a top.

The paperwork says failed number 7 connecting rod bearing. New engine. New radiator. New fuse block. Lots of new hoses gaskets and fluids.

Cost me zero dollars. (And three weeks of aggravation). No idea what the plan is going forward. As far as I understand it, drivetrain warranty is 5 years. So I guess I’m not in a big hurry.

John

 

[BacDoc]

Well it sucks to go through that but at least you are back on the road with a new engine.

Just curious about the history on your truck. Assuming you are first owner? What grade of gas do you use and how many oil changes in 22k miles?

Not sure any of that matters but it would be worth knowing. I’m running 93 premium and did first oil change at 1000 miles and drive aggressively when it is safe. Love my 6.2l so far!

 

[Johncunningham]

It’s the wife’s car. Lot of in town/suburban car pool miles. A few long trips. 3 oil changes. 22k miles in 13 months…I assume she puts 87 in it. I have been known to use the right pedal when I drive it. She loves it. I like it.

 

[iamlegion]

It’s the wife’s car. Lot of in town/suburban car pool miles. A few long trips. 3 oil changes. 22k miles in 13 months…I assume she puts 87 in it. I have been known to use the right pedal when I drive it. She loves it. I like it.

I would ask, she may not even know better.
Just put premium in…. Why drop $70k+ on a truck and then skim out at $1/gal especially after one engine issue.

 

[Nautilus571]

Owners manual specifically states to use only premium grade fuel. Anything else will result in issues with the engine.... I have a 2019 Sierra Denali with 44k mi and the 6.2L L87. Love it. The only issue recently like in say the last several thousand miles is oil evaporation. Shortly after an oil change say after 40% usage I am down 2 qts. Can't figure it out. No runs, no drips, no smoke.

 

[BattleTank]

Isn't high octane fuel suppose to prevent pre-detonation in high compression engines?

If so, why isn't the ECM seeing knock via the knock sensors and changing the ignition timing?

 

[DocDoug]

Owners manual specifically states to use only premium grade fuel. Anything else will result in issues with the engine.... I have a 2019 Sierra Denali with 44k mi and the 6.2L L87. Love it. The only issue recently like in say the last several thousand miles is oil evaporation. Shortly after an oil change say after 40% usage I am down 2 qts. Can't figure it out. No runs, no drips, no smoke.

Yep, 6.2 requires premium fuel. This is exactly why I chose the 5.3 for my 2022 Tahoe. I love my Tahoe!

 

[KMeloney]

Isn't high octane fuel suppose to prevent pre-detonation in high compression engines?

If so, why isn't the ECM seeing knock via the knock sensors and changing the ignition timing?

It probably is, and so you'd think that it should run better on more octane.

 

[Antonm]

Isn't high octane fuel suppose to prevent pre-detonation in high compression engines?

If so, why isn't the ECM seeing knock via the knock sensors and changing the ignition timing?

The PCM is pulling ignition timing, but its called "pre ignition detonation" so it's happening before the spark plug fires, as such changing when the spark plug fires can only do so much.

The big advancement with the LS engines (carried on with the LT's) that not many talk about is that GM reversed the flow coolant. In the ole-school GM V8's the cold water from the radiator went to the engine water jacket first and then flowed up to the cylinder heads. In the LS and later engines the cold water cools the heads first, then goes down to the engines water jacket. This improved cooling to the heads making them more resistant to pre-ignition detonation and allows more compression for the same octane fuel.

Remember though these are direct injection engines, so the computer can (and does) change when fuel is introduced into the cylinder. So the computer can not only adjust ignition timing, but it can also adjust fuel timing.

Between the lower temp cylinder heads/ combustion chamber afforded by the coolant routing, and the ability to control both ignition & fuel timing, you'd think these engines would be pretty good at limiting detonation.
...

 

[ChrisYukon]

The PCM is pulling ignition timing, but its called "pre ignition detonation" so it's happening before the spark plug fires, as such changing when the spark plug fires can only do so much.

...

This. The computer can only override the laws of physics so much...