Knock sound in intake

[WVRigrat05]

Been putting a lot of miles on the truck and opened it up pretty good going home the other day, truck has had what I thought sounded like a faint rod knock but after having someone hold it to 1700 rpm in gear I have a knock sound coming from the intake, sides and bottom of motor are silent, truck runs really good but it has sounded like it has a miss under light throttle and on decel, curious to what you guys though, the knock sound is horrible at times and not hardly noticeable at others, which makes me think an injector but I’m betting a rocker arm screw is backing off.

 

[duramax on fire]

Our LLY did the same thing and noise when an injector was going out. No noise wide open. Sounded bad off throttle and light load


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[WVRigrat05]

Oil pressure is down about 5-8 psi cruising but it still has Dino oil and it’s been real hot here, balance rates look good but main injection timing in gear is 14 mm3, it was quiet when we went to eat a few minutes ago, shut it off, then idled for 20 minutes and it got loud a minute and now it’s back to a faint slapping sound again, I’m not sure where to start.

 

[2004LB7]

I would throw a crap load of injector cleaner at it and cross my fingers

 

[WVRigrat05]

I’ll take a video and upload it, it’s got a slight miss in the exhaust, wfo it sounds fine though.

 

[PureHybrid]

If it's an internal issue it won't get worse and then better. I'd look at the fuel system like said, maybe double check wiring too.

 

[WVRigrat05]

Here’s some videos
https://youtu.be/xpHHCCbhf3c
https://youtu.be/Ie6L7iKBrNg

 

[2004LB7]

Sounds like a nice running engine to me. Maybe the mic doesn't pick it up very well but I dont hear anything out of the norm

 

[WVRigrat05]

How’s this one, sounds like a hammer
https://youtu.be/ET02KSEHIf0

 

[2004LB7]

Sounds like one injector/cylinder knocking on that one bit still kinda hard to tell

Throw a quart of 2 cycle oil in the fuel tank and see if it helps

 

[jlawles2]

Do you have a way to do injector cut out testing? Turn them off one at a time to see if the noise goes away or changes indicating where to start.

One other thing to check is the intake to the turbo to see if something got injected and is bouncing off the impeller.

 

[Hambone]

Sounds like mine did awhile back
Ran it to a quarter tank added a bottle of sea foam and gave her hell!!!
Took my #7 injector from being like +8 to back around +2 with the rest
Was honestly surprised It worked
Hope it’s something easy for you Reger... you seem to have some bad luck with these things :/

 

[WVRigrat05]

I’m going to change the fuel filter and a pile of power service, if it keeps it up I’ll pull the valve covers and check valve lash and go from there.

 

[PureHybrid]

Yea maybe the camera isn't picking it up, sounds like a regular duramax to me

 

[WVRigrat05]

There may be nothing wrong with it, but it’s louder than it was before tear down, and the sound has gotten worse,plus it’s been so long since I’ve been around another Duramax that’s not stock I forget what they sound like

 

[trashygasman]

I’m having the same issue with my LBZ after doing head gaskets this winter. Mine sounds like loose rockers to me. A guy who works on a lot of diesels told me valve lash isn’t that important but I also have to take a lot of what he says with a grain of salt sometimes. All I know is that it sounds different than it did before I tore it down...louder to me.

 

[onebaddmaxxx]

I’m having the same issue with my LBZ after doing head gaskets this winter. Mine sounds like loose rockers to me. A guy who works on a lot of diesels told me valve lash isn’t that important but I also have to take a lot of what he says with a grain of salt sometimes. All I know is that it sounds different than it did before I tore it down...louder to me.

Yours is probably in need of the valve lash needing done. Anytime iv heard a pop through the intake its always that, esp being yours happened when head gaskets were done..

 

[trashygasman]

Yours is probably in need of the valve lash needing done. Anytime iv heard a pop through the intake its always that, esp being yours happened when head gaskets were done..

Well I did it myself First time adjusting any valves in a looonnngg time, much less a diesel LOL....soooo I wouldn’t be surprised if they need readjusted. Can it be done by just pulling the top half of the valve cover?

 

[onebaddmaxxx]

Well I did it myself First time adjusting any valves in a looonnngg time, much less a diesel LOL....soooo I wouldn’t be surprised if they need readjusted. Can it be done by just pulling the top half of the valve cover?

Yes

 

[WVRigrat05]

Got my knock figured out, 2,000 mile fuel filter felt like a bar bell, we drained the tank and put fresh fuel in it, had a little fine black shit that settled out but nothing that looked alarming or terrible.

Now, from what I’ve read, the balance rates do not read while moving but mine do wheather they’re accurate or not, but injector 3 stays between 2.8 and 4.4 when cruising and levels out to 1.6 at idle and injector 2 will go as high as 3 moving idling it’s a .8.