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Engine knock a 500 miles

bass mechanic
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Fretmaster New Member

Fretmaster

Posted
Posted

I have this exact same knock in my 2020 Denali 2500. I just took it to the second GM dealer today and they gave said a GM bullitin claims it is normal. First dealer claimed it was something normal in the intake, second dealer claims it goes away after 20% oil life usage so that would indicate engine to me..  (I've only got about 200 miles on it) I was pretty confident that it wasn't an engine issue, but it is not a noise Ive heard in my previous diesels so it's not the normal sound.. It's very annoying.. 

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bass mechanic
bass mechanic

heres a video with the sounds  

Sask Farmboy
Sask Farmboy

My first chime in for this topic. My 2020 Denali DRW is being built in 2 weeks so I will be checking it out closely. I used to be a Chevy tech and finding stuff like this was my life. I

MN6.2
MN6.2

Didn't they have to change the back of the engine to accommodate the new 10 speed transmission? Doesn't seem like enough to create a knock like that but that is one major thing they changed. 

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dwoods123 Enthusiast

dwoods123

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Got it back from the service department after having them put the rubber strip on the roof and determining the knocking noise.  They said it was normal.  Said it has been around for years and nothing to worry about.  We tried to argue it was a new noise for this year's model but the service writer said no, it was not.  We asked where it was coming from and he gave us a vague answer of "internally in the engine".   I guess at least they documented it which was the goal  and if something flies apart down the road, we have proof it was looked at and deemed "normal" .  He did say there was a tech bulletin out on it but I seriously believe it was an old bulletin for the ticking noise  that has been out there for years.  This is not the same thing.....

Anyone else get the same answer?

bowtie2007 Enthusiast

bowtie2007

Posted
Posted

Well, this is my first diesel so i don't know any different but i have the TSB which says it is normal. I will try to get it later and attach the info.

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Sonny James Enthusiast

Sonny James

Posted
Posted

I put 550 miles on my new 3500HD Denali yesterday.  When picking it up new at 45 miles, there was a faint thumping/clunking noise.  After putting 550 miles on it is more noticeable when standing outside the truck.  So far I don't hear it in the cabin especially with the stereo going.  I do have another issue that I will post separately that I believe it is an issue with the transmission.  

 

Here is a snippet if anyone else wants to comment:

When doing 73-75 miles per hour I hear a hollow howling type noise that seems to come from the front right of the truck.  My passenger stated he thought he felt the floor vibrating and it sounded like it was coming from the rear.

 

What I have learned is if I put the transmission in manual shift, when doing 74 and then downshift from 10th to 9th the noise goes away.  If while in 9th gear I slow down to 68, the noise comes back until I downshift into 8th.  When hearing this noise the tach is exactly at 1500RPM.  Also, at times of acceleration if I hear the noise at lower speeds and look at the tach it is at 1500RPM.  I believe for every gear, if there is a speed that is hit that puts the engine at 1500RPM, I will hear the noise.  Crazy!!

dwoods123 Enthusiast

dwoods123

Posted
Posted
2 hours ago, bowtie2007 said:

I realized the TSB is already on here.

It is on here but for "ticking".  If that is the one they are referring to, it is incorrect.   This is a knocking noise much louder than the ticking issue.  I thought that must be the one they refer to but try and argue with them and it is a losing battle.  I say get it documented and move on as at least that way, if anything comes of it,  you will have proof you tried to point it out in the beginning.   

Shawn J. New Member

Shawn J.

Posted
Posted

I got a 2020 High Country Duramax and it does the same exact thing as the video at idle. That is the reason I am on here. I had a lot of Duramax trucks including  two 2017 LP5's. I am used to the 70K 1970's tick...lol but this is like an engine knock and very annoying to say the least. I have 200 miles on mine. I guess it is normal from the other posts on here so I feel a little better. I was going to go back to my dealer and listen to another one to see if it does it but I guess I will just wait to see what GM eventually says about in a service bulletin.

MrGraff Enthusiast

MrGraff

Posted
Posted

Same noise on mine with 7200 miles, haven't had any issues other than the random check engine light that will come on and go away randomly after several drive cycles.  

 

They changed transmission, injection system, oil cooler, bigger fan/radiator... pretty sure Gale Banks did a comparision video and listed off most of these items.  It's a 2020 new platform and powertrain combo so there is bound to be some glitches or hiccups, best thing you can do is get the noises etc recorded at a dealer so if anything ever comes up they have it on record for warranty purposes.

Roadrunner45 Enthusiast

Roadrunner45

Posted
Posted

Update on my 3500 with the knock. I put 500 plus miles hoping the sound  might vanish with the added miles but it didn't. Took it to my dealer for further evaluation and they told me today they were going to replace the oil pump, when the dealer first opened a case file with GM for the unknown noise they said the oil pump was a potential source. No ETA on the part coming MI will update the thread when the repairs are complete hopefully the pump is the culprit. Very happy that my dealer took this seriously and didn't try to say this was a normal sound.

bass mechanic Enthusiast

bass mechanic

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Update on my 3500 with the knock. I put 500 plus miles hoping the sound  might vanish with the added miles but it didn't. Took it to my dealer for further evaluation and they told me today they were going to replace the oil pump, when the dealer first opened a case file with GM for the unknown noise they said the oil pump was a potential source. No ETA on the part coming MI will update the thread when the repairs are complete hopefully the pump is the culprit. Very happy that my dealer took this seriously and didn't try to say this was a normal sound.

That is interesting I’ve been wondering if 30 PSI is really sufficient oil pressure for this engine at normal driving speed. I suspect a diesel requires less pressure because I think the rod and crank journals are wider than gas engines.


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Roadrunner45 Enthusiast

Roadrunner45

Posted
Posted

I know my previous LMM  oil pressure at normal operating temps would vary with RPM around 22 psi at idle to 44 psi at 2000 RPM. The factory gauge in the instrument panel didn't mimic my edge insight that was hooked into the OBD port there was always a considerable difference the same with the engine temps. I want to get a Banks  I-dash in short order. It's nice knowing what the real figures are not to mention being able to monitor so many other parameters, and have the ability to clear codes as well.

 

dwoods123 Enthusiast

dwoods123

Posted
Posted
On 1/23/2020 at 4:35 PM, Roadrunner45 said:

Update on my 3500 with the knock. I put 500 plus miles hoping the sound  might vanish with the added miles but it didn't. Took it to my dealer for further evaluation and they told me today they were going to replace the oil pump, when the dealer first opened a case file with GM for the unknown noise they said the oil pump was a potential source. No ETA on the part coming MI will update the thread when the repairs are complete hopefully the pump is the culprit. Very happy that my dealer took this seriously and didn't try to say this was a normal sound.

Glad to hear someone is getting a dealer to do something about it!  Let us know the outcome and if it cured the noise!  Ours is back in for it's first service and to get the fender light replaced due to moisture inside of it.  Hubby is going to bring up the oil pump as a possibility and tell them the bulletin they mentioned is for "ticking" not a knock.    Probably will not do any good but we will keep on them!  

dwoods123 Enthusiast

dwoods123

Posted
Posted
On 1/23/2020 at 4:35 PM, Roadrunner45 said:

Update on my 3500 with the knock. I put 500 plus miles hoping the sound  might vanish with the added miles but it didn't. Took it to my dealer for further evaluation and they told me today they were going to replace the oil pump, when the dealer first opened a case file with GM for the unknown noise they said the oil pump was a potential source. No ETA on the part coming MI will update the thread when the repairs are complete hopefully the pump is the culprit. Very happy that my dealer took this seriously and didn't try to say this was a normal sound.

Any news on the oil pump fixing the knock?  Just wondering if that is the problem we are all experiencing.   

Roadrunner45 Enthusiast

Roadrunner45

Posted
Posted

The pump came in last week. I placed the truck in the shop on Wednesday of that week . I thought it might have been complete on Monday-Tuesday this week but was informed it would now be Friday before I get it back,will update this thread after I get the truck back.  

 

Roadrunner45 Enthusiast

Roadrunner45

Posted
Posted

To update on the disposition of the repairs.  The good news is the thumping seems to be less pronounced than before but still present. In park and drive at slow speeds it seems a tad bit less than previously. I used to hear the sound through around 4-5 gear that seems to have been corrected at least in the short drive from the dealer to my home. Going to put it to the test tomorrow and tow my 14,,500 pound 5th wheel almost 700 miles. 

I will update of any changes from my first impressions.

I was really hoping this was the fix my service department said that a few with this issue had been corrected by the pump replacement but not in this case. The tech would did the work stated the the bottom end of the engine looked great no shavings in the oil, blue-ing of the rod caps etc.

 

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