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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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50 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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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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50 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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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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50 Posts
Discussion Starter · #51 ·
All great points, thank you all. I'm climbing back into more diagnosing this weekend. I've been driving it daily with lots of seafoam in the tank, and 8 ounces in the oil. How far can I push the seafoam / oil ratio for a short period to make sure the insides are clean? I'll then drain, new oil, filter, new oil cooler lines, connectors, seals etc. Then start finding that noise. No noise at cold startup, loudest is 2 minutes after cold start, that's what you hear on the recording, noise drops continuously until full engine temp and it's just a single tap, tap, tap and almost can't hear it at idle. Engine and new trans run great, I would love to nail this down so I'll stay on it.

Thanks for all the comments and tips, I'll follow up as soon as I can.

Jim P
 

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All great points, thank you all. I'm climbing back into more diagnosing this weekend. I've been driving it daily with lots of seafoam in the tank, and 8 ounces in the oil. How far can I push the seafoam / oil ratio for a short period to make sure the insides are clean? I'll then drain, new oil, filter, new oil cooler lines, connectors, seals etc. Then start finding that noise. No noise at cold startup, loudest is 2 minutes after cold start, that's what you hear on the recording, noise drops continuously until full engine temp and it's just a single tap, tap, tap and almost can't hear it at idle. Engine and new trans run great, I would love to nail this down so I'll stay on it.

Thanks for all the comments and tips, I'll follow up as soon as I can.

Jim P
The Directions on the Seafoam can state " Add to Oil 100-300 miles before every oil change" so dump the can into the crankcase and drive it, for up to 300 miles, then change the oil and filter.
 

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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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50 Posts
Discussion Starter · #53 ·
Thank you OkDually. Yes, did that and lots in the tank. Changed oil and filter yesterday. No change in noise. Swapped in a new injector through the banks, no change either. Valve train..I have a tool coming to pull lifters with the heads on. Will isolate noise source with valve covers off, new pair of lifters and pushrods coming this week to swap through. This weekend.. Thanks again. Jim P
 

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Thank you OkDually. Yes, did that and lots in the tank. Changed oil and filter yesterday. No change in noise. Swapped in a new injector through the banks, no change either. Valve train..I have a tool coming to pull lifters with the heads on. Will isolate noise source with valve covers off, new pair of lifters and pushrods coming this week to swap through. This weekend.. Thanks again. Jim P
Have you had any luck on the noise?
 

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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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50 Posts
Discussion Starter · #56 ·
Finally had some time late today. Pulled the top manifolds off, removed fuel lines and valve covers, put fuel lines back on and got it primed and running. I'll pull each rocker set (4 valves worth) and check lifters, pushrods, lifter brackets etc. All lifters are pumping oil into the rockers and putting pressure on the rockers one at a time to eliminate any gap makes no difference in the tap at all. I'll start digging downward. It's so frigging loud you would think it would be obvious where it was coming from. With the covers off, it does sound like its the driver side. I'll update when I can.. Here is the sound tonight, warm engine.

Jim P
 

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This is just a off the wall guess but do you have a exhaust leak at the manifold? Some of the reefer units that I work on sound very similar to that when they have cracked manifolds or blown out gasket
 

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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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50 Posts
Discussion Starter · #58 ·
I'll check and re-torque. Both manifolds were replaced new in the last year. Thanks!

Jim P
 

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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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50 Posts
Discussion Starter · #59 ·
Well....Nothing I do makes any difference. So I'm buttoning it back up and until spring/summer and I'm just going to drive it. Thanks for all the comments and ideas, I greatly appreciate it. When I re-visit and actually find anything, I will update!

Jim P
 

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1995 Chevrolet Silverado Z71 6.5 TD
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While it running put the palm of your hand on the rocker arm at the push rod area and push down and see if the sound changes. I remember my dad doing that to locate if the valve train was the culprit of a noise. You also should be able to use a long screw drive to locate the noise to at least the cylinder If you already have not done that.
 
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