2020 6.6 Liter Gas Engine Problems

[Bill Shaffer]

In 2020 I purchased a new Silverado 2500HD.   Vehicle has the GAS 6.6L Engine.   It recently had it's second Oil Change and Service.   Vehicle ONLY has 6,500 miles on it.   Now it has a knocking noise when idling.  I took it back tot he dealer where I purchased it.  They have had it for over a week.  Initially told they had no idea what the noise was.  They were communicating directly with GM to diagnose the issue.  As of now they have replaced engine bearings and dropped the Oil Pan with no loose or metal particles in the Oil.

With all of that said and done the noise is still present and they are waiting for further instructions from GM.

Just curious if anyone else has had this issue?

 

[mtnbiker1185]

I have the same truck with less than 5,000 miles and haven't noticed a knocking. I also made sure to use full synthetic when I did the oil change. While it may not seem like that should matter on an engine with such low miles, I had a Hemi previously and the only way to keep it from doing the infamous 'Hemi tick' was to use full synthetic. Completely different motor, I know, but still worth a shot. If you didn't do the oil change yourself, don't assume they used full synthetic either even though Chevy specifically calls for it. 

2020 was the first year for that motor so it is possible it has it's own version of the 'Hemi tick'. 

[Leem]

Hate to bring this back from the dead. Specially being my first post. But i recently changed my oil using OEM filter and quality oil. I changed mine at 3k miles its a 2021 6.6 gas custom. And now i have a slight knock random only in park and neutral. Oil pressure is about 38 to 40 psi hot idle. I used a stethoscope on my heads and everything sounds good. I am baffled sitting there with the door open you can here a random knock or clank similar to  a lifter but not like a AFM  collapsed  lifter on a half ton.  Set parking brake in drive no noise return to park or neutral and i will have a random tap/knock sound.

 

Dunno has me stumped went out and floored it oil pressure goes up as should no crazy sounds. no missing at idle or stumble. noise is not associated with rpm.   Kinda crazy sold my 1500 at 39k after AFM lifter repair after dealer had my truck for a month.  

 

If any body ever has a chance to listen to there truck in park after a drive right around the bell housing and oil pan location for a faint but audible knock/clank sound please chime in. 

[Stand By]

It was reading about the 6.2 having a second batch of bad lifters and valve springs.  Some of the 6.6 were affected the first time around. Take it to the dealer for a check. They should be able to detect misfires that you wouldn't be able to on your own.

[Leem]

Yes i have read that as well. Along with something about a fuel line with a check valve in it making a noise. And for it to be replaced. mine was built in June 2021. but still could have a valve train issue. Anyways if i take it in i will report back in what they find. In case this becomes a 6.6 issue 

 

One thing i am  sure of its certainly not like my 1500s collapsed  afm lifter or any broken valve spring noise. That can be found on the youtube. Not much info out there on these motors yet in the way of issues. 

[Brian Gemmill]

Hello!  I own a 2021 3500hd 6.6 gas cab&chassis with what sounds like the same noise.  A random light knock noise from the bell housing/rear engine block area only in park or neutral, hot idle started right after my first oil change at 2400 miles. I currently have 2600 miles and noise hasn't changed much in that short time.  User "Leem" explained my concern better than I can.  My local dealer is stumped.  Has anyone else had any further developments?

[Leem]

Hey Brian I would not worry to much about it. Like I mentioned when i changed my oil at 3000. I am now at 5600 miles and the noise stopped after about 1000 to 1200 miles on the new oil. Dunno drove me crazy. Then i did some research completely unrelated in Duramax forums. Those guys were experiencing same similar noise. They all said give the oil some time to get some mileage on it.  So I did even know it makes no sense to me two different worlds . And it went away. 

 

I have towed 6k to 9k multiple times . Taken the truck thru the gears full throttle a bunch. during my search for the noise. Taken my valve covers off to check for cracked springs. All this while racking up miles on the new oil and one day it was just gone. 

 

I though the noise was bell housing trans pan related but my scope led me to upper back of block maybe fuel pump cam lobe and hydraulic lifter spring driven pump area.  

Edited January 19, 2022 by Leem

[Tireman10]

Yep got a 6.6 gas 2500 2021 tik knock at idle around bell housing area, goes away in drive and reverse. But with no load on it its there, i hope someone can find out the problem 

[Tireman10]

On 4/5/2021 at 1:04 PM, Bill Shaffer said:

In 2020 I purchased a new Silverado 2500HD.   Vehicle has the GAS 6.6L Engine.   It recently had it's second Oil Change and Service.   Vehicle ONLY has 6,500 miles on it.   Now it has a knocking noise when idling.  I took it back tot he dealer where I purchased it.  They have had it for over a week.  Initially told they had no idea what the noise was.  They were communicating directly with GM to diagnose the issue.  As of now they have replaced engine bearings and dropped the Oil Pan with no loose or metal particles in the Oil.

With all of that said and done the noise is still present and they are waiting for further instructions from GM.

Just curious if anyone else has had this issue?

 

 

[Tireman10]

Same knock just wanted to see what they came up with 

[Tireman10]

Has anyone been told by GM or anyone with motor knowledge, what this might be ,get it out there and lets see what it is these are great motors and we need to get to the bottom of it

[Stand By]

Where's the egr valve on these things? They tend to worry a lot of people with their knocking, on various vehicles.

[Tireman10]

Egr don't knock. egr on the 6.6 gas is built in to drivers side valve cover up front and runs to intake right above TB ,there is alot of vacuum on it and pulls alot of contaminants from engine  block, be worth your while yo put a catch can on and a good one trust me all are not the same , RXP is a good one good luck

[gemarsh]

16 minutes ago, Tireman10 said:

Egr don't knock. egr on the 6.6 gas is built in to drivers side valve cover up front and runs to intake right above TB ,there is alot of vacuum on it and pulls alot of contaminants from engine  block, be worth your while yo put a catch can on and a good one trust me all are not the same , RXP is a good one good luck

I think you are confusing the pcv for the egr.

[Tireman10]

Ys you are correct the 6.6 gas i believe has no egr if someone knows different  let us know