7.3 knock

[vanillavanwinkle]

Plan on pulling valve covers soon, also have a parts truck coming tonight so at some point I'll be tearing into this one, I'll let yall know what I find. If anyone else has any ideas of what to check before I pull the engine, I'm happy to hear em!

 

[vanillavanwinkle]

Well parts engine is out, pulled the valve covers on my truck and found a very worn out rocker, swapped that and no difference in noise. Messed around with the timing, no difference. New injectors again, no difference. Put a stethoscope on it and I can only hear the knock in the bellhousing and valve covers. Kinda thinking maybe a lifter, but next step is just pulling the engine and tearing it down

 

[Nero]

Knock like that makes me wonder if there's a bad rod bearing....

 

[vanillavanwinkle]

Knock like that makes me wonder if there's a bad rod bearing....

Sorry I completely forgot to mention, the truck had all the bearings redone maybe 40,000km before it started knocking, they were all done .10 over. However, the previous owner did it all himself, and with the fact that all the pushrods and rockers were super worn, doesn't give me hope that anything was redone properly or torqued to spec

 

[Nero]

I'd pull the pan then, my instinct is to always recheck what was touched last. Usually it's culprit.

 

[WrenchWhore]

I'm very curious what you find. I hope it's relatively easy to fix and not a major overhaul. My original 6.9 I pulled out of my 87 was making a knocking sound. Very similar to what yours sounds like. Did Injectors, compression test, CDR, timing etc. nothing helped. I still need to tear it down and find out the real issue. Outside of the noise it ran great and was pulling 17.5 MPG.

 

[ihc1470]

Have you tried turning the engine over by hand and if so could you feel any difference as each piston makes it to TDC? Might need to pull the glow plugs to kill compression to make it easier to turn. I am wondering if by chance you have something on top of a piston. Have you pulled the wire to fuel shut off valve and cranked the motor if so how even does it crank and can you hear the noise under those conditions. Does the noise frequency change with RPM changes?

What were the compression readings? What makes the shop think #8 might have an issue? The injectors that went in what was the pop pressure and spray patterns like. Where they new or remaned or just some others you had on hand. Any work done to the engine shortly before the noise showed up?

It does seem odd that the knock stops as you drop each cylinder.

 

[vanillavanwinkle]

Have you tried turning the engine over by hand and if so could you feel any difference as each piston makes it to TDC? Might need to pull the glow plugs to kill compression to make it easier to turn. I am wondering if by chance you have something on top of a piston. Have you pulled the wire to fuel shut off valve and cranked the motor if so how even does it crank and can you hear the noise under those conditions. Does the noise frequency change with RPM changes?

What were the compression readings? What makes the shop think #8 might have an issue? The injectors that went in what was the pop pressure and spray patterns like. Where they new or remaned or just some others you had on hand. Any work done to the engine shortly before the noise showed up?

It does seem odd that the knock stops as you drop each cylinder.

I have and everything feels fine, I have the glow plugs soaking with some penetrating oil before I pull them just cause I know they love to snap off, I've decided to just pull the motor anyway because the thing is nasty so id like to redo gaskets and paint it and all that, so I'll probably pull the GPs once it's out. I have unplugged the FSS, it seems to crank even and I can't hear the noise without the engine actually running. The noise does seem to become a little bit softer sounding as RPMs climb, changes from a heavy knock to more of a tick.

Honestly the shop it was at didn't really seem to know much about the IDIs and they were a little sketchy, i never got any actual readings or reasoning behind their findings, it was just "crank and combustion pressure OK, cylinder #8 seems to be the cause of knock." I haven't had the injectors pop tested, but I bought a set of brand new ones (think they were delcos) and had a set from a running truck, also swapped around all the old ones and nothing seemed to make a difference at all. It just had an oil change done on it maybe 2 weeks before, but nothing else I can recall

 

[vanillavanwinkle]

I have new findings. The press fitting from the turbo into the exhaust completely blew out the gasket, could that possibly cause the knock I'm hearing? When it started knocking, it seemed like the truck actually gained a little bit of power, and also definitely stopped smoking from the exhaust so much, but did start chooching outta the engine bay quite a bit on startup when the engines cold. I would just start it up now that the turbo is off, but I've unhooked all the fuel lines and wires in preparation for pulling the engine, don't really want to go through the hassle of reconnecting everything if there's no way that's what it was. To me, that also makes sense as to why the knock gets quieter when any of the injectors are unhooked

 

[Nero]

There's no gasket in that slip joint, its a common leak point. Won't be reason for knock.

 

[Isaac Ristow]

Exhaust leaks can mimick engine knock but usually it's gotta be at a port on the manifold not a midway point. My guess is worn valve guides atleast to me in the video it sounded like the "knock" was coming out your tail pipe as well. I doubt it's rod knock that wouldn't run that long knocking and not even get a ton worse if it did. Onto another story when I got my c30 that I now have a perkins in it had a gm goodwrench 6.5 in it that suposibly had less than 10,000 miles on it. It make a wierd noticeable knocking noise it was most present on deceleration but I could notice it all the time made this noise since i got it till i yanked the engine never got worse. I yanked the 6.5 tore it all down everything looked brand new I was expecting to find a wrist pin bushing or something to be bad but I couldn't find anything so I said F it that engine is cursed so I got a 6.2 went though it and had that in there awhile it sounded good. I still wish I woulda known what was bad

 

[vanillavanwinkle]

Engine is out and pan is off, i found a decent amount of sideways play on cylinder #7 just grabbing the connecting rod and shifting it side to side. To me that seems normal, but think that could be it? Gonna take the heads off and pull pistons to inspect properly as well

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[Nero]

When you say side play, are you talking about parallel with the crank or perpendicular? Some parallel play is normal, there's a spec for it I'm sure.

 

[vanillavanwinkle]

When you say side play, are you talking about parallel with the crank or perpendicular? Some parallel play is normal, there's a spec for it I'm sure.

Parallel play, yeah that's kinda what I figured. Gonna pull heads and check wrist pins and valves n all that tomorrow

 

[vanillavanwinkle]

Okay so passenger head is off, nothing really looks out of the ordinary to me except for a really small sort of ridge in the rear passenger cylinder, but it's smooth so not sure what that's about, bad honing job maybe? Gonna pull pistons and valves on that side tomorrow and check those. Anything look out of place to anyone?