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The extension on the line is for a obsolete way of checking ip pressure, that line is shorter than the others by the lenght of that fitting, it is not causing the knock i assure you. It serves no purpose and is flow through. It was removed and another fitting installed during testing . Remove it and replace that line and your knock will still be there....
 

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1993 chevy silverado c3500 crew cab dually
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Something told to me years ago (I believe by OK)

New does not mean good. Yeah he was right!

A lighter valve spring. Maybe a slightly dangling valve Ford Triton style. Extra slop on timing chain. Or even the timing chain not being lined up correctly.

I had a bad IP can be noisy as hell! Bent pushrod slaps the side...
 
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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #43
Hey there Sparky. I could not agree more. My surprise with this is that the sound you hear now is "exactly" the same sound we started with. Exactly. No change what so ever. So I'm trying to make sure that I have looked at every single possible source of that sound before I start the teardown of sections again. Something for all to think about. What would be your sequence of checks and tests if you had a noise like this and you wanted to isolate it's source? I'm an open book guys, continued input on diagnostic sequence is greatly appreciated
!
 

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I've had similar issues, but on loud diesel farm equipment. It usually, for me, ended up being a vibrating guard, panel, etc vibrating at certain engine speeds. It's amazing how convincing a lost bolt or tool in an engine valley /out of sight location can be when making specifically misleading sounds. My step dad has told me for thirty years, "if it ain't broke, don't fix it."
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #45
Yep. I have some property couple hundred miles north of here, 20 acres. 1958 IHC diesel dozer, 1965 Deere diesel backhoe. I believe in the same statement. But something is broke here. With a noise like that, I'm not comfortable towing a travel trailer 1500 miles. Got to find out what...
 

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1994 K2500 Suburban 6.5 turbo.
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Hey there Sparky. I could not agree more. My surprise with this is that the sound you hear now is "exactly" the same sound we started with. Exactly. No change what so ever. So I'm trying to make sure that I have looked at every single possible source of that sound before I start the teardown of sections again. Something for all to think about. What would be your sequence of checks and tests if you had a noise like this and you wanted to isolate it's source? I'm an open book guys, continued input on diagnostic sequence is greatly appreciated
!
Have you tried cracking injector lines open one by one to see if the sound changes at any certain cylinder?
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #47
Have you tried cracking injector lines open one by one to see if the sound changes at any certain cylinder?
Yes. Crack an injector and idles falters. It's not an injector. Metal on metal, tap, tap, tap.
 

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Have you turned the motor by hand to feel for slop, if it's a piston pin, bearing, etc, you will be able to feel or hear a "loose" spot, back and forth on the crank bolt or alt pulley bolt, it will feel like a thump.... and pulling the pan may be the better way to go...
 

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Yep. I have some property couple hundred miles north of here, 20 acres. 1958 IHC diesel dozer, 1965 Deere diesel backhoe. I believe in the same statement. But something is broke here. With a noise like that, I'm not comfortable towing a travel trailer 1500 miles. Got to find out what...
That is some serious equipment for 20 acres. I guess if you're going to do it, go all out.

I just found the video clips you posted and watched them. That second video...that was some bone chilling audio. That sounds terrible. It's a no-load tap of some kind. Seems when you roll off the throttle it's very pronounced.

If it walks like a duck, sounds like a duck, etc---- That sounds like a rod bearing or a valve lifter to me, plain as day. Sounds like an old Ford on a cold winter morning mixed with a healthy Detroit. I know you measured, I know this stuff is new, but darn it it if you missed one measurement, or didn't measure enough positions around a crank journal, or something... That second video makes it sound like an old worn out engine that is on its way out.

It is definitely something worth investigating or pulling it apart---again, before something happens.
 

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Yep. I have some property couple hundred miles north of here, 20 acres. 1958 IHC diesel dozer, 1965 Deere diesel backhoe. I believe in the same statement. But something is broke here. With a noise like that, I'm not comfortable towing a travel trailer 1500 miles. Got to find out what...
Ya know I worried a lot about that exact same noise on every startup since I got my engine together, but the catastrophic failure I was expecting hasn't happened. On the contrary, the old beast has been very dependable despite long, hard miles doing stuff like hauling a camper from Seattle to the artic circle and back.

I've come to the conclusion what we're hearing might be colliding flame fronts of combustion, or injector noise, due to the viscosity of cold diesel. I've run a couple 6.2s on SVO or used ATF; cold they sounded like they were about to self destruct, but normal once up to temp.

I think the noises you really need to worry about are ones that get louder as the engine warms up.
 
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