2008 6.7 Cummins Engine Knock

Joesixpack said:
Sounds like the big end of a rod double tapping when you rev it up. Frequency seems to quick to be in the valve train.

Did you throw your head under it for a listen?
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Figured that's what it sounded like.....crank's going to have to be cleaned up no question. (I suppose a dick might polish it up with emery and throw it in a auction......)

For those that diagnosed correctly where's our prize?.....LOL
 
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Joesixpack said:
Figured that's what it sounded like.....crank's going to have to be cleaned up no question. (I suppose a dick might polish it up with emery and throw it in a auction......)

For those that diagnosed correctly where's our prize?.....LOL
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Your prize is one of the following, mailed to an address of your choice in the lower (48):
1. (1) piece of the broken oil ring
2. (1) half of the spun connecting rod bearing

:welcome:
 
The owner is looking for a used rod for sale, does anyone have one?

**I know this isn't the for sale or wanted to buy section but one of you guys has to have a used rod laying around. **
 
I suppose you can't just resize that one due to it being cracked cap can you, just thinking out loud.
 
What needs to be done, is obvious. The real question is, what caused it? It's hard to tell from the pics, but it sure looks like detonation. I would have that injector checked.

Paul
 
Pictures of the crank after removing 0.008 from the crank with a loop of 180 grit paper, when we started the crank was measuring right at 2.719" meaning it had 0.002" of build-up from bearing metal transfer.

It looks like it will be almost 100% cleaned up at the first oversize bearing dimension -.25MM.

CrankBearing1.jpg



CrankBearing2.jpg



To give perspective on the remaining damage to cut out, the horizontal scuffs are from slipping the micrometer on and off the crank a couple times to ensure we maintain roundness and an even cut. So far, it's producing satisfactory results.

CrankBearing3.jpg



CrankBearing4.jpg
 
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And how are you keeping the journal perfectly round and true while turning it with emery cloth?
 
For the record, I question how you cleaned up that journal.

To me it looks like there are 2 bands around the journal yet. I'm not sure how that will work long term. I would at least plastigauge it across the whole surface.
 
The owner was not able to get those two remaining bands in the middle cut out at the first oversize dimension around 2.706" so it looks like .020" total is getting cut off the journal.
 
Big Blue24 said:
The owner was not able to get those two remaining bands in the middle cut out at the first oversize dimension around 2.706" so it looks like .020" total is getting cut off the journal.
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Snap!!
 
Keep your fingers crossed, this thing is going back together next week!!!!

It's either going to sling a rod in 5 minutes or go another 100K miles!
 
Why not buy a good used crank or have it turned the right way and save a block. All the time you spent could have bought a perfect used one in the wages easy. I guess it is true you can't fix stupid. If you want I would gladly take the block and rebuild it correctly and have my spare like I want.
 
Its not going to sling a rod unless you forget to torque the bolts down or something. Im sure it will last a long time, the bearing shell might have some weird wear to it due to the possibility of an uneven cut. but that wont show up for a while. Props to ya for getting it done inframe and on a budget.

I wouldn't call this guy stupid coorsman...
 
Truck was fully reassembled last week, fired up, and ...........

No more knock, good oil pressure, and truck runs like it should. There was a lot of manual labor put into the crank to get it smooth and true, but the end result was a smooth-true journal.

If it were my truck, I probably would have bought a new crank and pulled the whole motor because my time is a little more valuable to me than the cost of a used crank. That said, if you're short on cash and have time available, you can do most anything!

Even cut 20 thousandths off a crank journal in-frame!
 
Glad it worked out for ya! Maybe you'll prove us wrong.
 
Any idea of what may have caused this? Ran low on oil? Contaminated oil? Or just bad bearings originally?
 
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