Engine Noise Bulletin of Interest

[Rail Boss]

May be of interest to folks with the engine knock/tap/tic with AFM. Melling (not GM ) released the attached bulletin pointing to oil pressure as the root cause of lifter noise. Please share if this is helpful.

Melling-tech-bulletin-on-GM-LS-Deactivation-Lifter-Issues-3.1.18-1.pdf

[2016 Sierra Owner]

This bulletin looks like it refers to the previous gen trucks 14-18. Not the new T1 series. The lifters and cylinder deactivation are controlled differently now from what I have seen. The bulletin has the wording of 4 control valves where as the new engines have 8. This link explains the differences.

 

https://www.chevyhardcore.com/tech-stories/engine/gm-escalates-cylinder-deactivation-with-dynamic-fuel-management/

[Rail Boss]

1 hour ago, 2016 Sierra Owner said:

This bulletin looks like it refers to the previous gen trucks 14-18. Not the new T1 series. The lifters and cylinder deactivation are controlled differently now from what I have seen. The bulletin has the wording of 4 control valves where as the new engines have 8. This link explains the differences.

 

https://www.chevyhardcore.com/tech-stories/engine/gm-escalates-cylinder-deactivation-with-dynamic-fuel-management/

The T1 series continues to offer the older design AFM 5.3 as the only V8 option for 2019 WT, Custom, and Custom Trail Boss.  GM 14-18 5.3 AFM had designation L83, Beginning sometime in 2018  AFM 5.3 got some updates which earned the new designation L82. Majority of the 2019 5.3 got updated to DFM and have the designation L84.  Here is a good article explaining the differences. https://www.onallcylinders.com/2019/07/19/l82-5-3l-ecotec3-engine-specs-performance-bore-stroke-cylinder-heads-cam-specs-more/

 

Sadly even the current L82 has the cold start knock issue. My 2019 Custom Trail Boss (3,150 mi) remains in a dealer parking lot with the issue continuing. After replacing 8lifters, I was told the noise is normal if it lasts less than 7 min, come pick it up. I refused to pick it up because the issue I brought it in for 3 weeks ago still exists. I told the service advisor to walk over to the new trucks start 3 of them up and if they all made the noise I would shut up. He declined the challenge.  GM maintains this is normal, no further warranty work authorized.