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Have any of you head a faint low frequency engine knock at idle from under the truck?

Seems like it doesn’t happen all the time but occasionally after it’s been driven and I start it up again.

 

 

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6.6 gas or 6.6 diesel?

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6.6 gas or 6.6 diesel?

Duramax


Sent from my iPhone using Tapatalk

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It's strange, the day I picked up my 2020 Duramax I noticed a loud knocking while it was running when I was parked in a parking lot. It was loud enough to hear in the cabin with the radio on. Drove it a few miles and it went away. I put another 150 miles on it and it hasn't come back.

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I just joined the forum to see about the knock i hear. It is faint at first start up but as the engine heats up it gets louder.

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I've got 700 miles on mine.  I've had the faint knock since day one.  Gets louder as truck warms up.  Tech at dealership told me some do it more than others but not to worry about it.  My 17 didn't do it.  Sounds like it is somewhat normal if others are doing it.

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Ive got the same hammering knock on my 2020.  I had it side by side with my 2018 l5P trade and it didnt have it.  I had the dealer pull another 2020 over and it had the same knock.  I figured it was related to some of the changes on the 2020 but it really hammers.

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Yep, I don't particularly like it  but I can live with it if it's normal.  Kinda like the duramax ticking and the transmission ticking while going through the drive thru that was on my 17. 120,000 on it with no issues whatsoever.  

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Any of these fit the bill?  Or, do you have any audio/video you can post here? 


 

Quote

 

#16-NA-372: Information on Duramax Diesel 6.6L Common Engine Noises - (Oct 1, 2019)

 

2017-2020 Duramax L5P

 

Tip: United States: A description of these noises and an audio file of what they sound like can be found in: 2018 SKH Seminar Feb Emerging Issues #10218.02V.

Canada: Dealers can review TAC Talk 52018.03D-0D March 2018 — Powertrain segment. Advance to timestamp 21:40 to view.

The following information describes these noises:

  • Rhythmic Ticking: This is a rhythmic ticking that can be heard during deceleration. The noise is usually, but not limited to, heard coming from around the passenger side of the vehicle. The noise is from the fuel injectors firing (one injector per deceleration and not always the same injector) and is a normal function of the engine and calibration system.
  •  
  • Parts Cycling Closed and Open: Some noises may be coming from under the hood after the engine has been turned OFF. You may notice that they are the same noises almost every time the engine is turned OFF. These noises seem to be coming from the turbocharger and/or the intake airlow valve. The intake airflow valve is a throttle plate actuator and is used to achieve high exhaust gas recirculation rates. These parts will cycle through their complete normal operating ranges after the engine is turned OFF. This is a normal operating condition.
  •  
  • Diesel Engine Tick: Diesel engine tick is present in all diesel engines produced in the last 20 years and does not have any impact on engine reliability and durability. It may be more noticeable on the 6.6L L5P because of the major reduction in combustion background noise. This occurs at idle and may seem to be louder when standing just behind the driver’s front wheel. The noise may be more noticeable in the first 20% of engine oil life.  Dealers should not attempt to compare any customer vehicles exhibiting this noise with other similar vehicles as the noise is different from vehicle to vehicle and this may lead to the incorrect conclusion that the vehicle has a condition. The noise is a normal operating characteristic and has no short or long term effects on the engine. DO NOT attempt repairs for this noise.
  •  
  • DEF Injector Noise: A tick noise may be heard coming from under the vehicle and typically it is heard at low vehicle speed and especially next to a building, such as when going through a drive through. The noise is from the DEF Injector and is considered a normal operating condition.

The information found in this bulletin can be shared with customers that may inquire about this condition. In the event they have additional questions or concerns, please advise them to contact Customer Assistance.

 

 

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It's not the ticking noise as described in the bulletin, its a knocking noise. I'll try to record it and post it. 

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Newdude, I'm familiar with all of those sounds, this is a new one to me and is definitely a knock sound and not a ticking noise.

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honestly i dont think for as long as this engine has been around this is a problem sound. diesels are noisy! if it was rod knock it would get louder with RPM and likely get worse under load.

and the fact others have the exact same sound, im sure any dealer will tell me its normal. ill wait till something bad happens and have it covered under warranty.

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This is my 5th diesel and none have ever sounded like this with the loud knock, and my 2020 does. I can't believe they changed anything from 2019 to 2020 that would cause this obnoxious knocking sound.

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