Lost the 6.2 (was: May have Lost the 6.2)

[zbad55]

There is no improved warranty...I have the special coverage under N25249003 which I have had since May. That is what it is giong to be. I appreciate the extra coverage, but I sure would ike to uderstand what has been done to mitigate the actual out of spec crankshafts and mitigate the sediment left behind. I'll always be nervous to drive this thing off the beaten path (like to my favorite fishing hole in Canada), which is the reason I have it in the first place.

As I have posted about this issue in the other long L87 thread and recently retired from GM but still have many contacts in engineering. The issue was sending the crank shafts to Mexico for machining of the crank shafts and quality teams from the U.S. not being allowed to travel and oversee this process. These cranks were all previously machined in the U.S., when GM decided to act on this to act on this teams of U.S. based engineering went to Mexico to remedy the issue.

The best thing that could happen for us was to fail the Pico test and receive a brand new engine with the new powertrain warranty. Depending on what your original crankshaft problems were like out of spec journals or debris in the oil ports will determine if the change in oil weight will "FIX" the issue. For me I didn't wait around for the testing of my 2023 Denali Ultimate as I didn't trust the testing, I traded it in for a good price and purchased a late build date 2025.

 

[viven44]

quality teams from the U.S. not being allowed to travel and oversee this process.

This hits home for me. I have always worked for semi-conductor (OE) manufacturers, and all the chip assembly factories are in Asia. I am not sure what GM's true rationale for not letting these teams travel, but assuming its travel cost and impact on bottomline. Depending on the quarter at Wall Street, we see extreme travel pressures and it just sucks trying to be a quality/process engineer when you are not allowed to travel and perform your job functions to the best of your ability. I think quarterly wall street earnings report are great for those that play the market game, but what a stress is puts on corporations and its employees.

 

[WalleyeMikeIII]

As I have posted about this issue in the other long L87 thread and recently retired from GM but still have many contacts in engineering. The issue was sending the crank shafts to Mexico for machining of the crank shafts and quality teams from the U.S. not being allowed to travel and oversee this process. These cranks were all previously machined in the U.S., when GM decided to act on this to act on this teams of U.S. based engineering went to Mexico to remedy the issue.

The best thing that could happen for us was to fail the Pico test and receive a brand new engine with the new powertrain warranty. Depending on what your original crankshaft problems were like out of spec journals or debris in the oil ports will determine if the change in oil weight will "FIX" the issue. For me I didn't wait around for the testing of my 2023 Denali Ultimate as I didn't trust the testing, I traded it in for a good price and purchased a late build date 2025.

Thanks for this info. Are you confident an engine built after Jun 1, 2024 has "in tolerance" Cranks?

What you say is what I would have expected the quality and engineering teams to do. And I hope my replacement engine is of high quality (at least the crank part of it). Did they move the crank machining back to Tonawanda, or just fix the process at the supplier in MX? Hopefully they also installed some incoming quality inspection of the cranks for debris and an occasional measurement for machining tolerance?

 

[WalleyeMikeIII]

This hits home for me. I have always worked for semi-conductor (OE) manufacturers, and all the chip assembly factories are in Asia. I am not sure what GM's true rationale for not letting these teams travel, but assuming its travel cost and impact on bottomline. Depending on the quarter at Wall Street, we see extreme travel pressures and it just sucks trying to be a quality/process engineer when you are not allowed to travel and perform your job functions to the best of your ability. I think quarterly wall street earnings report are great for those that play the market game, but what a stress is puts on corporations and its employees.

My gut says it was COVID that pre-empted their travel...Either way, guessing the bottom line is not liking the result, and a different process will be used in the future.

It is so frustrating, because having bottom end engine failures in a GM small block was really rare in the not too distant past. GM knows how to make engines...

 

[WalleyeMikeIII]

Enterprise Rent a Car called, after talking to the dealer, they have a Tahoe for me (finally). So taking the Courtesy transportation Sierra back to Dealer and getting the Tahoe. At least they are doing what they can. (Hope the tahoe has the 5.3 )

 

[zbad55]

Thanks for this info. Are you confident an engine built after Jun 1, 2024 has "in tolerance" Cranks?

What you say is what I would have expected the quality and engineering teams to do. And I hope my replacement engine is of high quality (at least the crank part of it). Did they move the crank machining back to Tonawanda, or just fix the process at the supplier in MX? Hopefully they also installed some incoming quality inspection of the cranks for debris and an occasional measurement for machining tolerance?

From what I have heard they are still machining the cranks in Mexico but have sent multiple teams down there to oversee the process and quality control. Yes I have confidence in this now and that is why I purchased a 2025, IMO as well as the people I have spoken with you have the best outcome that you could ask for. From speaking with the salesperson involved in my trade in, mine also passed the PICO test and given an oil change and then sold it to a new customer. I just didn't want to be driving around in a vehicle that has a badly machined crankshaft, good luck to you and I hope you get your vehicle back soon

 

[Vladimir2306]

From what I have heard they are still machining the cranks in Mexico but have sent multiple teams down there to oversee the process and quality control. Yes I have confidence in this now and that is why I purchased a 2025, IMO as well as the people I have spoken with you have the best outcome that you could ask for. From speaking with the salesperson involved in my trade in, mine also passed the PICO test and given an oil change and then sold it to a new customer. I just didn't want to be driving around in a vehicle that has a badly machined crankshaft, good luck to you and I hope you get your vehicle back soon

I'm going to upset you, but 2025 cars are also out of order.

 

[B-train]

I'm going to upset you, but 2025 cars are also out of order.

Agreed. There was a reddit post about somebody's 2025 Denali that died at 23xx miles (or thereabouts) for the same reason as all the other 6.2L. They plastered a big sign to the rear window after getting it back saying date and mileage of failure as a warning to potential buyers - creative way to let out frustration I thought.

I think there will be more added to the list, but fingers crossed for those who have later production dates.

Edit: see screen shot

 

[Vladimir2306]

Reddit has many cases of the the PASSED test that then failed shortly thereafter - yukon, trucks, etc. I think it's a publicity stunt band aid to try and buy time/limit the financial loss.

I talked about this right when the PICO test and 0-40 oil change campaign started. It doesn't help; it's a scam. 0-40 oil won't help in this situation either. The problem is much deeper than simply changing the oil to a thicker grade.

 

[Vladimir2306]

Engine bearing quality and crankshaft finish is technology that has been understood for well over 40 years now. We used to supply GM with Main and Rod bearings for many years. I have seen the process from design to testing. At least up till 2019 when I left as the company was bought out. Maybe the new owners let the true engineers go??? Maybe the new owners decided it was cheaper to bring in bearings from China, manufacturing was split between the USA/ Michigan and Mexico when I left.

GM claims the crankshaft finish was less than perfect and that could certainly cause issues, maybe GM relaxed crankshaft finish so they could build new cranks 5% faster? Maybe they went off shore for bearings and the new supplier did not have the technology needed to make functional parts?

Hard to say without getting actual engineers that have the knowledge to look at the bad parts. The parts will tell the story. I have looked at thousands of failed engine bearings in 40 years. Sometimes a microscope was needed and small particles could be retrieved from the used parts. Those particles could be examined and determined exactly where in the engine the particles originated. It is not magic. How to determine the cause is a well documented process. At least it always was up until 2019 when I was last aware of process used.

In the old days once the parts were designed before GM would accept them as a production run actual dynometer tests were done on multiple running engines and they were put under thousands of hours of testing to see when and how they failed. They were exposed to low octane fuel to watch how they held up under detonation, exposed to high RPM tests, put in severe driving tests, tested with perfect oil and less than perfect oil. Everything was known and proven before GM accepted the design.

Ford insisted on a 300 hour wide open throttle test on new piston designs! That was over 12 days wide open throttle with the engine at max HP RPM on the dyno, if max hp was at 5600 RPM it would run there wide open throttle for over 12 days to meet the 300 hour test. There were about 8 dynomometer's in the bearing lab, 26 dynomometers in the piston ring lab, more in the piston lab, many more at the gasket lab These demanding tests were used to test many parts, everything from spark plugs, water pumps, injection systems, gaskets, bearings, rings, pistons. Everything had to work to run the engine under heavy loads for extreme testing.
I remember the engineers even introducing nitros to engines to determine failure points if an engine did not fail in normal testing.

I understand computers have taken over much of the actual testing and when done right all is still well. GM dropped the ball with these 6.2L engines, to continue building engines with these bearing problems over a few years is absolute negligence. They ignored the problem hoping it would only affect a smaller number of engines. All parts we supplied had to have identifiers stamped on them. You could pick up a used part and know what plant built it, what day, month and year it was built and what shift built the part that day. If there were problems you could trace it back and determine what went wrong on that specific day. In manufacturing parts were checked multiple times before shipping, visual inspections and electronic inspections were done. Core samples were taken to verify the metallurgy on schedule during production. The ball was dropped at GM or standards were relaxed causing this issue.

The engineering department at GM knew the cause and made it known to corporate GM management long before the public heard anything. GM gambled most of the engines would get out of warranty and lost. Now they are trying to present a positive spin to keep customers. OK, I feel better after sharing what little I know about engine parts supply and manufacture, keep in mind my information is going obsolete since I have not been involved at all since 2019. I would still trust the replacement engines. No way would they not fix the actual issue before shipping more engines. ( they might use up the existing inventory first but newly produced engines will be good ). We have not read of any supplier being blamed (yet) which says it was not the bearings fault they are failing.

Bearing liners are simply the first to take the impact. Look at the photo; this is what bearings look like. Look online for photos of the causes of bearing wear; it's clearly not oil or improper installation. It's clearly wear due to contamination of the bearing and crankshaft running surfaces.
Even if you install new connecting rod bearings without replacing the radiator, oil pump, and oil lines, wear debris begins to wear down the red bearings. The second photo shows a track showing wear along the oil flow.

 

[WalleyeMikeIII]

Bearing liners are simply the first to take the impact. Look at the photo; this is what bearings look like. Look online for photos of the causes of bearing wear; it's clearly not oil or improper installation. It's clearly wear due to contamination of the bearing and crankshaft running surfaces.
Even if you install new connecting rod bearings without replacing the radiator, oil pump, and oil lines, wear debris begins to wear down the red bearings. The second photo shows a track showing wear along the oil flow.

Agree. That is about exactly what I would expect to see if the cranks were improperly machined. The Second phto with the red bearings looks more like some contamination wear, but could also be a bad spot of machining on the crank, hard to know without seeing and inspecting the crank.

 

[Vladimir2306]

Agree. That is about exactly what I would expect to see if the cranks were improperly machined. The Second phto with the red bearings looks more like some contamination wear, but could also be a bad spot of machining on the crank, hard to know without seeing and inspecting the crank.

I've already mentioned here that our service department examined the crankshafts of various GM engines inside and out. They cut them open, examined their hardness and hardening, and looked at the metal composition. There are no changes with the 4th-generation 6.2 engines, or with the 5th-generation engine... Moreover, after rebuilding the engines, the clearances were adjusted, and the engines were assembled correctly. With cleanliness and quality workmanship, there are no failures on the old L87 crankshafts. So, no, GM's tales about crankshaft machining and some factory are nonsense.

 

[RogerK]

Headed out after work tonight, was going to head to Costco after work. Started up the Denali, drove about 2 miles, started hearing a loud knock/rattle from the engine. Sound reminded me of a playing card in the bicycle spokes. Pulled over, put it in park, could clearly hear the knocking, it varied with engine RPM. My GMC dealer was about 3 miles away, so I gingerly drove it to them, pulled in the service drive. Service manager popped the hood and listened. He said, "Definitely coming from the engine. This is a 6.2, right?"

I answered, 'Yes, of course."

He said, "doesn't sound good. I don't want to send you out of here with it."

My service advisor wrote it up, said they don't have a loaner right now, but offered the shuttle to take me home. He said after diagnosing tomorrow, he will call. If it is the engine, they will get me a looaner or a rental.

Details:
Odometer at 44,780
Recall was performed and passed pico test in June at 38k, been on 0W-40 since then.
Had a paid oil change at 43,200 about 2 weeks ago, along with front and rear diff fluid change, transmission fluid and filter, transfer case fluid, and replaced the battery.

Engine still ran when I left the dealer at 5:30, but is knocking badly. Guessing I'm in for a new engine, but we will see tomorrow; I'll keep you all posted.

Mine took 2 1/2 months engines are behind in assembling

 

[Ltop]

Headed out after work tonight, was going to head to Costco after work. Started up the Denali, drove about 2 miles, started hearing a loud knock/rattle from the engine. Sound reminded me of a playing card in the bicycle spokes. Pulled over, put it in park, could clearly hear the knocking, it varied with engine RPM. My GMC dealer was about 3 miles away, so I gingerly drove it to them, pulled in the service drive. Service manager popped the hood and listened. He said, "Definitely coming from the engine. This is a 6.2, right?"

I answered, 'Yes, of course."

He said, "doesn't sound good. I don't want to send you out of here with it."

My service advisor wrote it up, said they don't have a loaner right now, but offered the shuttle to take me home. He said after diagnosing tomorrow, he will call. If it is the engine, they will get me a looaner or a rental.

Details:
Odometer at 44,780
Recall was performed and passed pico test in June at 38k, been on 0W-40 since then.
Had a paid oil change at 43,200 about 2 weeks ago, along with front and rear diff fluid change, transmission fluid and filter, transfer case fluid, and replaced the battery.

Engine still ran when I left the dealer at 5:30, but is knocking badly. Guessing I'm in for a new engine, but we will see tomorrow; I'll keep you all posted.

Mine happened at 47,000 and have had the engine replaced by dealer. They too had no loaner, took 2 weeks to get back with replaced engine. 0W-40 seems to be a bandaid to prolong eventual failure

 

[zbad55]

Bearing liners are simply the first to take the impact. Look at the photo; this is what bearings look like. Look online for photos of the causes of bearing wear; it's clearly not oil or improper installation. It's clearly wear due to contamination of the bearing and crankshaft running surfaces.

So, no, GM's tales about crankshaft machining and some factory are nonsense.

So exactly what do you mean here about nonsense of the improper crankshaft machining. These 2 post looks like are they are contradicting one another so I'm not sure where you are getting your information about the cause of this. I'm just passing along info from the engineers who are involved in this big mess, now I hope that the recall doesn't get expanded to 2025 but there may be some early 24 builds that are 25's. But in no way do I believe that GM kept cranking out bad engines thru September 25 when they switched to 26 model year.

 

[Marky Dissod]

0w40 seems to be a bandaid to prolong eventual failure.

This, exactly. 0w20 is barely good enough, and 0w30 or 0w40 is better, but if the engine doesn't make it past 200,000 trouble-free miles,
blame GM, as GM looks to pass the buck.

 

[Stbentoak]

You would think with ALL THIS debate over factory specified 0W20 vs ANY other weight oil, that some independent lab would take say 10 correctly built engines with no debris in them and run them thru some accelerated wear tests on dyno's and disassemble and prove conclusively that: YES 0W-20 IS inadequate and you'll be lucky to get past your powertrain warranty.... or No, if properly maintained there is no reason oil related that the engine couldn't go 100+ to 150+K miles or more with no real wear issues...

 

[KMeloney]

Mine took 2 1/2 months engines are behind in assembling

When did you get yours replaced?

 

[Antonm]

You would think with ALL THIS debate over factory specified 0W20 vs ANY other weight oil, that some independent lab would take say 10 correctly built engines with no debris in them and run them thru some accelerated wear tests on dyno's and disassemble and prove conclusively that: YES 0W-20 IS inadequate and you'll be lucky to get past your powertrain warranty.... or No, if properly maintained there is no reason oil related that the engine couldn't go 100+ to 150+K miles or more with no real wear issues...

Testing requires money, and the results of that testing would need to be financially beneficial to someone before they'd flip that bill.

But there is, IMHO, enough field data to say pretty certainly that under ideal conditions (no manufacturing defects present or abnormal use) that an 0W20 is adequate. Plenty of vehicles have ran it for years. Your normal soccer-mom/ grocery getter vehicles (assuming they had no manufacturer defects) would most likely live an acceptable service life using 0W20.

But (and there is always a "but"), throw in a little real world / non-ideal conditions, maybe some towing or some spirited driving, or some GDI fuel dilution, or some frequent start-stops at operating temperature (the list could go on, but I think we get the idea) and the margin to adequacy get used up pretty quickly.

0W40 is not a miracle cure all, but it does provide more margin to damage and there is literally no downside to running it. There is no plausible case where an 0W20 does a better job than an 0w40 at protecting the engine, there are cases where they two may be equal, the 0W20 will never be better.

Think of it like using a 12K lb rated hitch ball vice a 6K lb hitch ball. If you're towing a 6k lb trailer, then the 6K lb hitch ball is adequate and you can run like that for a long time. But using a 12k lb rated hitch ball in that same scenario would have absolutely no downside, and provide an increased safety margin should something not be perfect.
...

 

[vcode]

You would think with ALL THIS debate over factory specified 0W20 vs ANY other weight oil, that some independent lab would take say 10 correctly built engines with no debris in them and run them thru some accelerated wear tests on dyno's and disassemble and prove conclusively that: YES 0W-20 IS inadequate and you'll be lucky to get past your powertrain warranty.... or No, if properly maintained there is no reason oil related that the engine couldn't go 100+ to 150+K miles or more with no real wear issues...

I have said that all along that there is no definitive proof that the 0W20 is the complete garbage many people say it is. Real world driving says it is just fine. People apparently just don't want to believe GM and their engineering analysis that bad cranks and excessive debris are causing the problem.....