LB7: Rotational knocking when engine is warm

[SpotlessDemo]

Hello everyone. I'm a new guy on the forum. Just bought my first diesel. A couple of weeks ago I bought a 2002 Chevy 2500HD Crew cab diesel (LB7) with 118,000 miles off of a private seller. He said the injectors were replaced over the past year. I took it for a test drive (from a cold start), and she ran and sounded great. Test drive took about 5 minutes, and most of it at neighborhood speeds. I agree to buy it, and I take it home; about 45 minutes of highway.

When I got off of the highway I noticed a rotational knocking. At idle I don't even notice it. In park at about 1,500 RPM I hear the knock. In gear it is noticeable as well when the RPMs break 1,500 +/-. When I start it from cold I don't notice it at all, but when it warms up it comes right back. No performance issues noticed, no check engine light, and no smoke.

I changed the oil and filter. Old oil smelled fine (no diesel smell in it), and looked clean. Replaced it with 10 qts AMSOil and and AMSOil filter. Again, injectors were said to be replaced within the past year.

Thoughts? Need valve adjustment? Pistons? Sell the truck cause it will be too much money? Haha (I hope not).

Thanks everyone!

 

[ripmf666]

Do you have any dtc codes ? Also check the flex plate could be cracked.

 

[SpotlessDemo]

No I don't have the DTC codes. I wasn't even thinking the fly wheel since I hear the noise the best with the hood open. Definitely sounds like its coming from under the hood. I listened underneath, but it doesn't seem to be coming from there.

 

[ripmf666]

Can you get a little video clip of it and post it up.

 

[Hot COCOAL]

As the oil in the engine warms, it gets thinner, right. Are you positive it is not typical noise for a LB7 or diesel in general, please take no offense, just asking. From what you describe the truck runs great.

 

[SpotlessDemo]

I'll do a video of it later today (work midnights and need a little sleep now). No offense taken Jason. I have driven a diesel ambulance (Ford) for many years, and I've been around others before. I know they make a lot of noise, and being concerned about it I took it to the local Chevy dealer. He said it sounds different too, but they won't even diagnose it because it has over 100k on it. I didn't know they would work on them over 100k, but oh well. I'll throw the video on later today. Believe me, I wish it was just a regular diesel noise. That's much easier on my wallet!

 

[dmax711]

Is it more of a ticking noise? Mines Had a slite tick forever, people describe it like a typwritter noise..

 

[Bonestock]

Do an injector balance test & also use dvt to cancel out cylinders. If you have efilive v2 you can do this otherwise find someone who can.:thumb:

 

[stacks04]

Being its an lb7 what emissions version is it? Look above the fuel filter housing for a bunch of vacuum lines and valves. The vacuum pump is very common to tick on the california emissions versions.

 

[SpotlessDemo]

My video is posted on YouTube at http://www.youtube.com/watch?v=Dx_SGxSohvg

I have to say it sounds more defined in person. It sounds like a rotational clicking that increases in volume and speed as the RPMs increase. As far as emissions it does not appear to be or say California emissions. As far as the injector balance test I'll have to get someone to do that for me as I don't have that equipment. I have a mechanic friend of mine that can help, but he doesn't have the equipment to test the injectors.

Only thought against injectors though is the truck runs like a champ, has no smoke, and no diesel smell in the oil. Oh, and sorry for the poor video location at the end. It isn't easy to hit the throttle and video under the hood.

Thanks again.

 

[Hot COCOAL]

Hey guys, i dont know how it would matter if the rig was warm ot not? But could this be a bad harmonic balancer?

 

[Hot COCOAL]

Is there evidence of performance mods? Dual fuelers on a stock block can shrink your rods, maybe a shot of nitrous? Definitely a curious one. It kinda bugs me that it changes when the engine oil is warm.

 

[SpotlessDemo]

I see no evidence of any performance mods at all. When the engine is cold, now that I'm tuned in to listening for it, I still hear it, but not nearly as pronounced as when the truck is warm, so its there, just not as noticeable. My thought about he valves is that the .012 spacing is to allow for expansion when they are warm (or so I thought), so maybe they are out of whack after this many miles and new injectors. I read a post yesterday of a guy who found then average spacing was .053 on his 210k motor. That keeps sticking in my head.

 

[Hot COCOAL]

Well if it is still there when its cold, i will fall back to the broken harmonic balancer idea, and hope its as simple as that for ya, sorry there is no difinitive answer for ya, typically thats how it goes, i have an issue at this time that has yet to be identified, it's now suspected that there is a problem with my ecm. One day i ran my truck into the garage, running perfect! Added a couple bolt ons, went to fire it up, and it chugged, and idled soo rough, the #8 injector was stuck open for no apparent reason, as it turns out the injector was fine, its somehow getting a faulty signal, the wiring tested out fine, so now its to the ecm
Keep movin farward, i guess.

 

[Bonestock]

Sounds just like the last lb7 I did. Cyl 4&6 injectors were gone. I bet if you shut Your cyl off one@ a time you will find the noise will go away.

 

[JMK777]

That sounds like a bad injector. check balance rates

 

[SpotlessDemo]

I thought bad injectors came with performance issues and smoke, and I thought I would hear it more at idle and have a check engine light. no? As far as the harmonic balancer, I thought you would hear that loud noise even at idle. I'm no pro at this. I'm just throwing in what I "think" I learned across the way.

 

[SpotlessDemo]

Okay, broke out the stethoscope. Over the valve covers all sounded normal except for the driver's side closest to the firewall. That part sounded hollow and with a rotational knock (faster and slower with the RPMs). I'm just assuming that eliminates the harmonic balancer and fly wheel. Back to what I hope is only a valve adjustment and not a nightmare. Any other thoughts?

 

[curt]

sure sounds alot like my lb7!!! i could still hear my valve train noise when cold but it got louder with a warm engine! my problem was a broken lifter guide bolt cylinders 6,8(pass side firewall) the exhaust lifters for some reason were worn way more than the intake! i could hear a slight popping noise as well from the intake filter! maybe check your intake for this noise, seems like a cylinder charge with pressure thats getting released when the intake valve opens! heres some photos:

hopefully its just a injector like others are thinking! :thumb:

tryin not to derail thread so will fill in some history! this is a lb7 with automatic trans,never exceeded 3500 rpm so not sure why bolt broke!

the wire is .030 mig welding wire i fed it thru the lifter body because the bottom of the lifter was knurled over so much i couldnt remove the lifter out of the bore, so i fed the wire thru the lifter and ot the camshaft bore then dropped the lifter into the galley above crank then pulled lifters out thru cam bore! lol what a job !!!!!

hope this info helps!

 

[Bonestock]

Injector.