LML engine knock

ikeG

ikeG

Oughta Know Better
Apr 19, 2011
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Got a 2016 denali with only 13,000 miles on it here that knocks when cold. See vid.https://youtu.be/huiF1SzO7ME Just stock trans and fuel system tuning. While running, disabling injector 3 changes the pitch of the knock. It doesn't go away until engine is warm. I swapped in 4 new injectors on passenger bank with no change. I now have the engine out and down to a short block.
Piston protrusion is all within spec. Cyl walls look good. You can tell something has ran thru it based on the cam lobes but nothing alarming. The pickup screen had this curled piece of assuming aluminum stuck to it. I have no way of measuring bore but take a look at these vids of rocking piston in their bores. Some are much worse(loose) than others. I pulled num 3 rod and piston out and rings and bearing look good. https://youtu.be/2p4A90ym-UE
https://youtu.be/LcIWBbuFen8
https://youtu.be/Op3IE7teBkw
https://youtu.be/IRjLWS80lP8

Its looking like I'll be stripping it down rest of way but I figured I'd post this up while taking a break here. I'm kinda worried at this point that I'm missing something or I'm not going to find anything.
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KyleC4

Tech
Dec 30, 2016
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So did you ask about piston to bore clearance seems loose or piston to wrist pin? I think I keep confusing myself when I read this. Not enough coffee yet. I’ll ask around some people that know of or have had issues. Only 16 I had issue with was pushrod broke where cup and shaft are mated.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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it very well could be piston slap you are hearing in the video, that generally only shows up when cold. as you pull each piston/rod out, look at the orientation of the piston. id be curious if the piston was put in 180* out from where it should be. if not, really look the cyl walls over on the loose cyl's and the whole oiling system that feeds it. might have a plug or restriction there.
 
ikeG

ikeG

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Apr 19, 2011
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KyleC4 said:
So did you ask about piston to bore clearance seems loose or piston to wrist pin? I think I keep confusing myself when I read this. Not enough coffee yet. I’ll ask around some people that know of or have had issues. Only 16 I had issue with was pushrod broke where cup and shaft are mated.
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Not sure if I asked a question or not lol. Just was brainstorming.

I have piston 3 out and went over it with a fine toothed comb. Also did same to all the lifters a couple times. I did check valve lash before disassembling and it was fine. I might have jumped the gun on posting since I have 7 more pistons to check but I had to take a break from it and may not start again until tomorrow.

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ikeG

ikeG

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Apr 19, 2011
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Not sure if I got anywhere but once I had all pistons and rods out(no visible problems with them) I can spin the crank over faster, which makes a whirring or clicking sound. I think I might have narrowed it down to the oil pump. Removed water pump first, no change. Removed oil pump drive gear, no noise. Hard to believe. Not convinced yet. Will have a new one tomorrow to compare. I cannot get the phillip's screws out of the back of the suspect one to save my life.

Also, Each upper rod bearing is worn more than I'd expect for 13,000 miles. One has pitting along the edge. Something to check if my oil pump doesn't change it. I'm also going to pull the cam for inspection since its this far down.

https://youtu.be/VFkS-LCrH7Y
https://youtu.be/DV9gpW-7xMA
https://youtu.be/dR2N-zEjz3s
4e1c92254a0418cc6b95053c91817b84.jpg


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ikeG

ikeG

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Apr 19, 2011
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Cp4 timing was off one tooth....

But I have installed one before without timing it at all with no problems, definitely no noises.

Cam looks great. Cam bearings have more wear than I'd expect, just like the rod bearings. Something's definitely been run thru the oiling system.

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Needmomoney

New member
Dec 16, 2021
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Old thread revival I am sorry. What was the issue ultimately? I have the same sound only when engine isn’t up to temp. Then it goes away.
 
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Needmomoney

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Dec 16, 2021
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F me man!!! You pulled that thing apart and it still did that 🤮. You still have it? Any issues afterwards? I’m hoping mine is ok. I just did head gaskets and a ton of other crap. Also, thanks for the reply!
 
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ikeG

ikeG

Oughta Know Better
Apr 19, 2011
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Western PA
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Needmomoney said:
F me man!!! You pulled that thing apart and it still did that . You still have it? Any issues afterwards? I’m hoping mine is ok. I just did head gaskets and a ton of other crap. Also, thanks for the reply!
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It was owned by a dealership. They sold it. Explained the concern to the customer and everything. Never heard back

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Needmomoney

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Dec 16, 2021
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ikeG said:
It was owned by a dealership. They sold it. Explained the concern to the customer and everything. Never heard back

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Gotcha! Well I’ll go with no news is good news! It’s just weird. Thanks again for letting me know that information!
 
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