Lifter question

[Quark]

Alas, the only ones who might have a clue aren't talking - the GM engineers. Is it unknowable or is it unspeakable.

 

[chirp]

I think there may be two causes of 2021 lifter problems. One is theoretical, and the other is published and acknowledged by GM.

1. Caused by AFM/DFM. This is a theory brought forth by many; no GM bulletin published on the subject to my knowledge (please correct me if wrong).
2. Caused by faulty parts (lifter collapse). This occurred for models built during specific months of the 2021 model year. I don't have the "bad" build months on hand; others may have that information.

 

[Quark]

Yet these failures have been occurring on pickups for the past two years. GM had a bad production run of springs but I've never heard of a bad run of lifters that has been acknowledged.

 

[Fireman591]

My dealer has replaced bent push rods with no broken springs or collapsed lifters. This sure sounds like harmonics on the push rods from a piss poor design. Oh and those bent lifters did have wear marks right in the area of the lifter sidewall where the push rod could make contact with it.

 

[Geotrash]

My dealer has replaced bent push rods with no broken springs or collapsed lifters. This sure sounds like harmonics on the push rods from a piss poor design. Oh and those bent lifters did have wear marks right in the area of the lifter sidewall where the push rod could make contact with it.

Yeah, the guy makes a pretty good case that weak pushrods are the smoking gun. But who knows? The engines with the older AFM system had essentially the same lifters, rockers, pushrods and springs, and their failure mode was lifters failing to fully engage and getting damaged, with the root cause being either a fault in the VLOM or low oil pressure not providing enough energy for the lifters to reliably engage. The valve train geometry is slightly different in the Gen V engines though, so maybe that's enough to make the pushrods the weak link.

 

[Micahsd]

According to this new TSB it shows the bad lifters were installed in vehicles between Sept 1, 2020 and March 31, 2021.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10197298-9999.pdf

 

[Quark]

I don't understand why a lot of us are trying to see the rosy side of this when we should be highly critical of a company pumping out an unreliable product. If you're a GM sales associate raise your hand otherwise smarten up.

"The aforementioned valve lifter problem affects 2019-and-later model-year..."

How GM Dealers Handle Engine Valve Lifter Issues

Affecting 5.3L L84 and 6.2L L87 V8 engines.

gmauthority.com

This does not suggest a bad batch of whatever but if it were a bad batch it is multi-year and GM's quality control is worse than a Yugo's. C'mon man!!!