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Discussion Starter #1 (Edited)
Hey Guys/Gals,
I have a 2018 Sierra 2500HD L5P with around 53k miles on it.

I am at my wits end with the incompetent dealership I have been working with and still don't have resolution with this. They have replaced harmonic balancer, water pump, both smooth idler pulleys, serpentine belt, and I STILL have this noise that sounds like a bearing squeal.

Since they weren't honest on their service invoice notes, I have just removed the accessory belt and started the truck and the noise is still there, so that I have confirmed.

Here is the video of the noise.
You will hear the higher pitched metal on meal squeal sound.

Have any of you replace that fan bearing pulley yet. That seems to be the only next culprit or its something else internal to the motor, which I don't think is the case since I would have seen other issues with engine performance. Thanks for your input and taking a look!
 

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Discussion Starter #2
Here is another perspective of the noise. Would you consider this a chipping noise? Would this be the HP4 pump?
 

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Discussion Starter #3
I have confirmed that the noise is present with the accessory belt disconnected, radiator fan disabled. After connecting those back up, I crawled under the truck and put a mechanics stethoscope up to an area 6 inches to the passengers side of the harmonic balancer on the flange and I hear a very distinct noise just like the metallic one captured in the video. The truck is schedule for a dealer visit (not the same one that had thrown parts at it before and told me that is normal).
 

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Check the mounting bracket for the CAC hose in that area.. Loose bolts or cracks?
 

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Discussion Starter #5 (Edited)
Check the mounting bracket for the CAC hose in that area.. Loose bolts or cracks?
Just went outside and checked this per your recommendation, I see the upper side is bolted on the mount, no issue up top from what I can tell. The bottom I am showing this leak. I am assuming I shouldn't have anything exiting this area right?
 

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I would clean it off good and recheck it. A little oil around the clamp over time is normal. I believe there is a TSB on noise coming from that bracket. Try and push on it and see if the noise changes.
 

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Discussion Starter #7
I would clean it off good and recheck it. A little oil around the clamp over time is normal. I believe there is a TSB on noise coming from that bracket. Try and push on it and see if the noise changes.
Started it again, noise was present. I moved that hose and it didn't change the noise. It seems to come from the area closer to the harmonic balancer.
 

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Sorry about your luck. I hope the dealer gets it right this time..
If thay tell you it's normal, then thay need to compare with another one and show you.
 

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I don't hear any chirping or squealing noise on either video.
 

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Discussion Starter #10
I don't hear any chirping or squealing noise on either video.
Hi Ron, I am likely referring to it with an incorrect adjective. Here is another video. If you listen the first 10 seconds, you hear a normal sounding diesel. Then drag the time indicator to 1:05 and listen for another 10 seconds or so. You will hear a high pitched noise that is constant. It may take you a minute to tune into it but its very distinct and separate from the what I would call normal engine sound. My disclaimer is this is always a challenge to capture on a phone microphone.
 

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I really don't hear anything but I work at a power plant and after 31 years well high frequencies are gone. I did just see a potential problem on the GM-TECHLINK called
Harmonic Balancer Sliding Back on Crankshaft
You might want to take a look at the balancer and see if it has shifted back and rubbing on the front of the motor. Check www.gm-techlink.com for more information.
 
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Discussion Starter #12
Here is another few videos of the sound that I took to get some fresh ears on it.



This sound should be that audible almost constant squeak noise.

This makes the same noise with the accessory belt off and the fan disconnected.
 

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Ok I do hear it now. Did you check the lower crank pulley clearance with the block?
 

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Discussion Starter #14
I did look up there and there is light and space between the pulley and block. The harmonic balancer was replaced about a month ago and the dealer didn't mention it was rubbing. Also, when I start the truck cold (sitting all night) it doesn't make that noise immediately. The noise is very noticeable and distinct when it is warmed up.

A few questions:

Could a bad crank seal make this noise?
Could a spun bearing make this noise?
Could Denso HP4 high pressure pump make that noise?

Just trying to think all options. Its wearing me down.
 

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Discussion Starter #15
Here is another close up video that I captured while under the vehicle. It also includes a shut down so you can hear the noise fade off.
 
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