2020 l5p duramax knock at idle cold, worse hot

Capt. Wackencracker

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Feb 22, 2020
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:confused:
Hi everyone. Just signed up to the forum.

I picked up my 2020 Denali 2500 hd duramax this week and noticed a loud knocking at idle which increases in volume as the engine warms up.
Went back in to the dealer before I even left the lot and saw the service advisor and the diesel tech who both said it was normal.
Now, I'm 70 years old and had my own repair business for 30 plus years and was a service manager for Oldsmobile, Buick, and Firestone, so I know a BS line when I hear one.
This is my 5th diesel. 3 Duramax, 1 Cummins, and 1 Cat.THIS IS NOT A NORMAL NOISE.
I visited GM-Trucks and on their forum "Rod knock at 500 Miles", there are many owners complaining about the exact same problem with some sound videos. Most all are getting the same run around with the dealers. I broke out the stethoscope and narrowed it down to the EGR area. Also emailed Gale Banks yesterday and waiting for an answer.
I would appreciate any feedback on this problem.
Thanks in advance for your response.
....CORRECTION....the site at GM-Trucks is..."Engine knock a 500 miles"
Yes it's "a" not "at"
 
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Capt. Wackencracker

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Feb 22, 2020
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Link update.
The link I previously described for others experiencing knock problems is...
...Engine knock a 500 miles"
Yes it is "a" not "at".
Thanks...:confused:
 

2004LB7

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Dec 15, 2010
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Where are you located? Sounds like you need to take it to a reputable shop that knows what they are doing

Rod knock is not very common for the Duramax but then again the L5P is compatibly new so it is possible. On the previous models It was more often an injector but would need to shut it off to know for sure
 

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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All I have is some timing rattle under throttle tip in, in the morning. Soon as I get around the block, she’s quiet.

Might have a noisy injector solenoid
 

Hoser

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Jun 18, 2016
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I know it’s an old thread, but the L5P in the 2020 is the noisiest, most unpleasant Duramax to date. The thumping, ticking, screeching, and what I’m assuming is injector knock, is almost Unbearable.
 

1lunger

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Mar 11, 2019
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Glad I got a 2019! Mines been fine and it’s going for a full delete next month. I’m at 52,577 miles and I’ve had the Banks kit from the beginning. I do love the truck, but I can’t wait for it to get the big “D”!! The only thing I didn’t like was it called for oil changes so often. The DIC would be at 5% oil life in less than 3500 miles. Sometimes not even 3k. I installed the Amsoil dual stage bypass filter kit and now I get about 10k between oil changes.


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Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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I know it’s an old thread, but the L5P in the 2020 is the noisiest, most unpleasant Duramax to date. The thumping, ticking, screeching, and what I’m assuming is injector knock, is almost Unbearable.
Been in 3 different 2020’s and besides when mine melted down a dpf, I’ve yet to hear a quieter Dmax from factory.

When the dpf melted down, the truck sounded like a lb7 with real nasty injector rattle like pilot injection was off. Once fixed, quiet as can be
 

1lunger

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What kind of miles were on the truck when you melted the dpf?


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Chevy1925

don't know sh!t about IFS
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5k. lets see how long this one lasts!

mind you, this is all mainly towing miles, foot to the floor up every hill, etc.
 

kiwilml

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Nov 4, 2015
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I've got 14k miles on my 20 now in 2.5 months and I'm super impressed with everything. The motor does make some knocking noises every now and then on coasting/ slow down but not much. I didn't even notice regens until I got my cts3 and was able to see them, which is a plus for me. By far the best stock truck I've ever had.

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Hoser

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Jun 18, 2016
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Farmington, MN
Been in 3 different 2020’s and besides when mine melted down a dpf, I’ve yet to hear a quieter Dmax from factory.

When the dpf melted down, the truck sounded like a lb7 with real nasty injector rattle like pilot injection was off. Once fixed, quiet as can be
Sure, once you Have your trailer hooked up and are under way cruising down the freeway with the cruise set, they are crazy quiet, even under acceleration. But let off the throttle and there is some mad injector knock during decel. But the worst is when it’s idling when loading the bed up, hooking trailers, rigging chains for pulling crap, the truck thumps and screeches and squeaks. I’ve talked to guys and read about many that have said the same thing.
 

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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Sure, once you Have your trailer hooked up and are under way cruising down the freeway with the cruise set, they are crazy quiet, even under acceleration. But let off the throttle and there is some mad injector knock during decel. But the worst is when it’s idling when loading the bed up, hooking trailers, rigging chains for pulling crap, the truck thumps and screeches and squeaks. I’ve talked to guys and read about many that have said the same thing.
Once again, I can not say I’ve seen or heard any of this??? Done plenty of decel for miles down grades and truck is always idling being the kids are in there. Buddy’s 19 is the same. Dunno, maybe something will come up down the road but so far it out does my 02 in both lb7 and lly form, brothers LMM and dads lml in the sound department.

The only thing I ever hear at idle is the def injector ticking away (could be more or less depending on soot load) and the occasional rumble from the exhaust from the ecm commanding a cane sweep like all the older models.
 

Hoser

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Jun 18, 2016
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There is a TSB on the thumping, as well as many threads on the matter on forums all over. There’s also threads on the injector or timing knock, I think there’s even one here. The guys I talk to with 2020 trucks say the thumping drives them crazy.
 

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