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04-11-2018, 04:19 PM
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#1
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Name: DDually
Title: Still spooling..
Status: Not Here
Join Date: Nov 2009
Member`s Gallery
Posts: 2,095
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04 Cummins problem, intermittent knock
I have a weird problem on a friend's 04 auto truck with 170k miles.
It has a noticeable knock when driving and rolling. It doesn't knock at all when it's sitting there idling in park, drive, reverse, or nuetral. It doesn't smoke at all, it has no notable blow by, and the oil pressure is good according to my mechanical gauge. I was thinking about pulling the valve train off to see if there is anything weird going on in there. Another thing to note is that it is matched with engine speed, not vehicle speed. It idles really smooth too, it doesn't feel like it's running on 5-1/2 cylinders or anything.
I was thinking maybe a cracked flex plate.
Is there anything else that would making a rod knock type sound?
Is it worth check compression if there isn't bad blow by?
Is it worth having the injectors sent off to be checked if it doesn't even haze at idle or cold start?
This is kind of a beat to crap ranch truck and it's been used and abused.
Short story: knocks when moving, no smoke, no blow by, doesn't knock when idling or sitting in drive.
Thanks,
Jared
__________________
1995 Cummins with almost no matching paint, 2 dents
2001 VW TDI South bend, tune, nozzys, custom stuff that's rusting, one custom thing that's not rusting
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04-11-2018, 04:23 PM
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#2
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Name: RacinDuallie
Title: Black Sheep Racing
Status: Not Here
Join Date: Apr 2006
Location: Supporting Northeast Diesel Racing
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Posts: 17,369
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Converter or flexplate bolt backing out?
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04-11-2018, 04:27 PM
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#3
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Name: SPEEDSHIFT
Title: Too Much Time
Status: Not Here
Join Date: Jan 2007
Location: San Antonio, TX
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Posts: 5,978
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I would check rail pressure and look for a spike when it starts the knocking. Could be a sticky FCA if thats the case.
May run a dose of Diesel Kleen through it as well, I have seen that fix similar problems.
__________________
@bodie_armstrong
2003 2500 4x4 auto FOR SALE
2005 2500 4x4 auto Drag Truck
2013 3500 4x4 Aisin Dually Tow Rig
Tenacity Tuning, Longs Machine Shop, BD Diesel Performance
Last edited by SPEEDSHIFT; 04-11-2018 at 04:29 PM.
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04-11-2018, 04:37 PM
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#4
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Name: SPEEDSHIFT
Title: Too Much Time
Status: Not Here
Join Date: Jan 2007
Location: San Antonio, TX
Member`s Gallery
Posts: 5,978
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Quote:
Originally Posted by RacinDuallie
Converter or flexplate bolt backing out?
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I have had that happen, it was to the opposite effect of his though. Rattled terribly at idle and cleared up under a load.
__________________
@bodie_armstrong
2003 2500 4x4 auto FOR SALE
2005 2500 4x4 auto Drag Truck
2013 3500 4x4 Aisin Dually Tow Rig
Tenacity Tuning, Longs Machine Shop, BD Diesel Performance
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04-11-2018, 04:42 PM
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#5
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Name: DDually
Title: Still spooling..
Status: Not Here
Join Date: Nov 2009
Member`s Gallery
Posts: 2,095
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Quote:
Originally Posted by SPEEDSHIFT
I would check rail pressure and look for a spike when it starts the knocking. Could be a sticky FCA if thats the case.
May run a dose of Diesel Kleen through it as well, I have seen that fix similar problems.
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Will do. Ill try both.
__________________
1995 Cummins with almost no matching paint, 2 dents
2001 VW TDI South bend, tune, nozzys, custom stuff that's rusting, one custom thing that's not rusting
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04-11-2018, 04:43 PM
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#6
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Name: DDually
Title: Still spooling..
Status: Not Here
Join Date: Nov 2009
Member`s Gallery
Posts: 2,095
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Quote:
Originally Posted by RacinDuallie
Converter or flexplate bolt backing out?
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I'm going to pull the inspection cover and check this as well. Never know.
__________________
1995 Cummins with almost no matching paint, 2 dents
2001 VW TDI South bend, tune, nozzys, custom stuff that's rusting, one custom thing that's not rusting
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04-11-2018, 05:17 PM
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#7
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Name: DDually
Title: Still spooling..
Status: Not Here
Join Date: Nov 2009
Member`s Gallery
Posts: 2,095
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Quote:
Originally Posted by RacinDuallie
Converter or flexplate bolt backing out?
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All the flex plate bolts are tight
__________________
1995 Cummins with almost no matching paint, 2 dents
2001 VW TDI South bend, tune, nozzys, custom stuff that's rusting, one custom thing that's not rusting
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