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Discussion Starter #1
Thumping sound heard at idle and increases with RPM as you drive. Can hear it easily when standing outside front or when listening near front wheel wells and from inside the truck. This is my 4th Duramax so I am familiar with all the ticking noise complaints but this is not a tick. Truck had 660 miles when I Left it with dealer and they said it was "EGR valve operation noise, normal coming from EGR system". None of my other trucks had this loud of a thumping sound. No codes and truck runs fine. Anyone else have this same noise?
Thanks,
Jhc
2020 Denali
2017 Denali
2015 Chevy LT
2008 Chevy LT
 

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Could it be the CP3 noise....? or a fuel pressure noise coming from somewhere?
 

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When I open hood I think recall a similar noise but it’s the air intake sound effects when hood open only.


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I hear it as well, but it seems to have gotten quieter as I put miles on it. (3000mi)
I believe it is fuel pressure related
 

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Discussion Starter #5
Yes most likely some type of fuel pressure problem. I know they stopped using CP4 pumps in 2017 and my 2017 was never this loud. I listened to another 2020 on the lot and it was much quieter than mine.
Hope it quiets down with more miles driven.
 

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Discussion Starter #7
Right, I hope it's not the pump, dealer blames the egr system. Not sure what normal egr valve operation sounds like. I think they all make the sound just that this one seems extra loud. Trying to hunt down another 2020 and compare it to mine.
 

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My egr doesn’t make any sound lol except when you turn truck off it cycles to “clean” itself


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I believe that is the vane controller you hear cycling not the egr
 

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I will ask the service dept to check on the vane controller to see if that is it. Got to be a simple solution but they always give you the "it's normal" for something like this. I googled "duramax noises" etc but can't find a similar sound on the u tube vids. A lot have injector problem sounds and knocking noises from older dmaxes but I couldn't find a match.
 

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Sorry, i was replying to the previous post. The vane controller cycles after the truck is shut off and sits for a short period of time. Never heard of an egr making any noise. I can hear a slight knocking when I decel but according to some great info on this forum , I believe that is injectors being regulated by ecm so not a problem-- hope you post what you find on yours.
 

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Discussion Starter #12
Thanks Sambor. I know what you mean about the vane noise after shut down. This thump or knock is always there not just on decel but at idle and excel. Just seems louder than my other dmaxes.
I will try to record the sound on my phone and post it. Not to tech-savy so I may need to have a 10 yr old help me out with recording and posting!
 

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Thumping sound

Just bought a 2020 3500 with a Duramax Thump thump thump from under the wheel wells and when I opened the hood it sounds like its up top on the drivers side. frustrating to say the least!
 

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My new 2020 Denali 3500 has the thump and it is louder than my brothers 2020 Chevy LTZ. The only difference is his has miles on it. So here is me Pray
 

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I have a 2020 Duramax with 500 miles on it. My brother was standing outside of it the other day and asked what the thumping noise was. I got out to listen and did hear it. I think it must be a normal engine noise for the Duramax or at least the newer ones.
 

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I took mine into the dealer for its first shake down visit and knocking aka thumping was on the list. The techs at the dealer said its a normal sound for the motor, regardless best to get it on record just in case.
 

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My 2020 Sierra 2500 Duramax has the same problem that you are describing. I noticed it just after taking delivery and brought it to the Dealership’s attention, they checked other 2020’s on the lot and advised that at least one other made the same thumping noise. At 7900 km the noise had escalated from a thumping to a definite knocking which now could be heard not only at an idle but also at higher rpm. Currently my new truck is in the shop where the Dealership is making adjustments to the valves. It’s been there for over a week I am hoping to get it back next week I will let you know if they are able to fix the problem. I should also add that this is definitely not the ticking sound that my previous Duramax’s made, I have put 900,000 km on GM Duramax equipped trucks and have never heard this sound. Sure would like to hear if anyone has figured out what is causing this noise.
 

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As promised here is an update on my previous post regarding the thumping/knocking noise many are experiencing with the 2020 GM Duramax. After having my new truck in the shop for two weeks and the Dealership tearing down the top end of the engine to complete adjustments to the valves, the Dealership advised that the problem was related to the clutch in the fan. I was surprised with this as one of the first things they did when they first started to diagnose the problem was run the truck with the drive belt removed which they did with no change in the knocking noise. So I have the truck back and have been told that they are now waiting for a plan for repairing the problem from GM. I will update this tread as soon as I hear what the plan is.
 

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As promised here is an update on my previous post regarding the thumping/knocking noise many are experiencing with the 2020 GM Duramax. After having my new truck in the shop for two weeks and the Dealership tearing down the top end of the engine to complete adjustments to the valves, the Dealership advised that the problem was related to the clutch in the fan. I was surprised with this as one of the first things they did when they first started to diagnose the problem was run the truck with the drive belt removed which they did with no change in the knocking noise. So I have the truck back and have been told that they are now waiting for a plan for repairing the problem from GM. I will update this tread as soon as I hear what the plan is.

the fan clutch??? sounds like someone doesn't have a clue, but i guess if it works that would be an easy fix. Keep us posted, the noise doesn't bother me but if there is a fix id have it done.
 

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I was surprised with this as one of the first things they did when they first started to diagnose the problem was run the truck with the drive belt removed which they did with no change in the knocking noise.
Fan has it's own belt on the '20, out past the drive belt, no?
 
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