LM2 Valve Clatter

LM2HC4x4

New member
Feb 21, 2020
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New to the forum.

Picked up my LM2 end of January. Began having what sounded like valve clatter around around 2k rpm. Assumed, it was potentially normal as the engine continued to break-in. However, it has continued to get worse. The dealership has opened a "Tact" case no answers at this stage as there are apparently no others issues like it. At cold start yesterday morning (about 30F degrees) definitely had more like an engine rod or main bearing knock.

The dealership diesel tech originally though it was normal diesel sound but has know come to the conclusion there is definitely an internal engine knock.

Will keep posted as we get more information. I will be dropping the truck off this coming Monday for continued test.

If anyone knows of anyone with the same issues. Let me know!

Thanks,
Richard
 

KyleC4

Tech
Dec 30, 2016
371
13
18
Bay Area
I have not heard anything yet of issues like what you are describing. And yes the “TAC” (technical assistance center) for GM is contacted for all new model vehicles. Engineering usually gets involved and wants to know. Could be a long road just so you know. Hang in there.
 

jp2000

New member
Feb 27, 2020
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I also have this clatter on my 3.0 LM2.

Gets pretty loud when slowly climbing hills. Going slow in a parking lot I can mostly avoid it happening.
Sometimes right after cold start up if I put it in fwd or reverse with the parking brake on to hold it, it will clatter away while I search relentlessly.
Sometimes after it gets warm and I get to my destination and I park I can hear it intermittently clacking. (not the typerwriter kind that plagues other engines)

Its loud enough to feel embarrassing coming out of your new truck, doesn't sound like part of the diesel sound. Like you I hope it will go away (not likely). I haven't had time to take it to the dealer yet.
 

jp2000

New member
Feb 27, 2020
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0
Was watching this guy's youtube and can kinda hear much of the same clatter noise on his startup. Is that what yours sounds like?

Not sure how to link vids, start up is at 49 seconds, real clatter comes in at 1:02

https://youtu.be/fRVjTby4cIs?t=49

2020 Silverado 3.0 Duramax Cool Weather features, startup and warm up (16F to 20F)
 

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
13,606
144
63
Mid Michigan
Could it be that GM set the valve lash too loose on those engines, or an adjuster nut has backed off in the valvetrain as you've put miles on?
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,609
184
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Phoenix Az
Was watching this guy's youtube and can kinda hear much of the same clatter noise on his startup. Is that what yours sounds like?

Not sure how to link vids, start up is at 49 seconds, real clatter comes in at 1:02

https://youtu.be/fRVjTby4cIs?t=49

2020 Silverado 3.0 Duramax Cool Weather features, startup and warm up (16F to 20F)
thats not valve clatter. thats fuel knock from either being real cold or lots of timing from it being so cold
 

jp2000

New member
Feb 27, 2020
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Yeah, that's a reasonable explanation. The problem is mine just makes noises like this when warm under light load.

Here's another more obvious clatter that is way easier to hear that sounds like my clatter.

https://youtu.be/C6Ug6AS9Le0?t=67

But once again this guy is cold start. If you heard this clatter under warm temperatures after the engine was warmed up, most noticeable under load, what do you think the problem would be? When he comes back from his drive, I can still kind of hear the abnormal clatter.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,609
184
63
Phoenix Az
I don’t know what you are expecting. I just hear a Diesel engine. You can’t expect it to be as quiet as a gasser
 

jp2000

New member
Feb 27, 2020
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0
0
Yeah, I've been thinking funky pilot injection. Sadly I don't see any relearn procedures for that with gds2, seems to help some cars. Still need to verify they put the right injector codes in at the factory. Wonder if they could even mess that up if they wanted to. These things are just probably extra clattery.

Thanks fast03
 

Seansmp8

New member
Dec 7, 2020
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0
1
I have the same rattling sound. It only started after the dealer replaced my coolant control valve. It’s so damn irritating.
 

Cansomike

New member
Dec 21, 2020
1
0
1
New to the forum.

Picked up my LM2 end of January. Began having what sounded like valve clatter around around 2k rpm. Assumed, it was potentially normal as the engine continued to break-in. However, it has continued to get worse. The dealership has opened a "Tact" case no answers at this stage as there are apparently no others issues like it. At cold start yesterday morning (about 30F degrees) definitely had more like an engine rod or main bearing knock.

The dealership diesel tech originally though it was normal diesel sound but has know come to the conclusion there is definitely an internal engine knock.

Will keep posted as we get more information. I will be dropping the truck off this coming Monday for continued test.

If anyone knows of anyone with the same issues. Let me know!

Thanks,
Richard
I have the same issue and I’m thinking it’s injection/combustion related. I still don’t like it though, especially coming from a new truck. I have to have a faulty coolant valve replaced this week and I’m going to mention it to the dealer.
 

steelman02

New member
Jan 6, 2021
1
0
1
Rome, Georgia
Hello all, I'm new to the forum.

I am having the same issue with the clatter, or sometimes knocking noise at low throttle. I have tried getting fuel from different stations to see if that would have any affect on it, but that made no difference. At times the knocking noise is very loud like a rod or something.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,658
21
38
At Da Beach
Has anybody tried a fuel additive yet? Diesel power service makes my LML so quiet you'd think its a gasser. I'd give it a shot, it's cheap and easy.
 

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