Rod knock, fuel knock or something else altogether? - Dodge Cummins Diesel Forum
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post #1 of 13 (permalink) Old 08-02-2018, 06:56 PM Thread Starter
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Rod knock, fuel knock or something else altogether?

Here's the deal, it's been making the same noise for 2k miles. Oil pressure has dropped a bit, but never zeroed out at any point. It sounds about half engine speed. I've heard some people say worst pin and piston slap, other say rod, some say fuel.

The noise only comes in around 1400 rpms and I dont rev about 2500 for any reason 99% of the time.

The motor was rebuilt and printed by me only 6k miles ago.

Can a rod knock for 2k miles, or am I missing something here? I've always thought rods knocked at idle up to redline, and piston slap was the same. Its worrying to me because I plan on taking the truck out to utah from NC at the end of September.

And for those who are curious, I'm going to change the oil and cut the filter this weekend.

https://youtu.be/qB8QQjFWVN8


97 2500, NV4500, 4wd. Rebuilt at 400k, .020 over, .010, .010 crank, A1 studs, AFC live, K27, DAP 5x.012, BHAF, 4k gsk, Hamilton 178/208, Air Dog, Valair Ceramic 12.5", Boost, EGT, Fuel Pressure
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post #2 of 13 (permalink) Old 08-02-2018, 08:00 PM
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I suggest you take an oil sample and send it in for analysis. If you have high wear metal numbers you will have your answer.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #3 of 13 (permalink) Old 08-02-2018, 08:01 PM Thread Starter
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Quote:
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I suggest you take an oil sample and send it in for analysis. If you have high wear metal numbers you will have your answer.
Will any old shop do an analysis?

97 2500, NV4500, 4wd. Rebuilt at 400k, .020 over, .010, .010 crank, A1 studs, AFC live, K27, DAP 5x.012, BHAF, 4k gsk, Hamilton 178/208, Air Dog, Valair Ceramic 12.5", Boost, EGT, Fuel Pressure
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post #4 of 13 (permalink) Old 08-02-2018, 08:33 PM
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Those while you wait desk top analysis stations are a waste of time and money. Lots of people us Blackstone labs. I use https://www.genosgarage.com/product/cc2525/oil-filters I get the results about a week after mailing the oil to the lab.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #5 of 13 (permalink) Old 08-02-2018, 08:47 PM
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Blackstone's have a pretty quick turn around and they will email you the results to get them quicker.

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post #6 of 13 (permalink) Old 08-02-2018, 10:53 PM
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Might be and injector doing that. My 96 knock bad when I bought it sounded like a rod was going to fly out of it but it was 2 bad injectors.

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post #7 of 13 (permalink) Old 08-03-2018, 10:17 AM
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I sent a sample to Houston on Monday morning and received the e-mailed results today. I buy the kits by the dozen from a different vendor (lower cost & free shipping) so I have them on hand all the time.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #8 of 13 (permalink) Old 08-04-2018, 09:44 PM Thread Starter
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Well, I drove it back to my parents house today to further investigate. At idle you can hear some sort of metallic knocking coming from the driver side, but nothing on the passenger side. I'm changing the oil tomorrow and I'll be sending off a sample to Blackstone Monday morning and I'll progress from there.

Injector knock might not out be out of the question. Technically speaking, the injectors I bought were remaned, so its entirely bad one of them or multiple have gone bad. I'll have to send them out for testing. Hopefully I can find a local shop near the trailer that will be able to do it for me.

Still not out of the water but one step at a time.

97 2500, NV4500, 4wd. Rebuilt at 400k, .020 over, .010, .010 crank, A1 studs, AFC live, K27, DAP 5x.012, BHAF, 4k gsk, Hamilton 178/208, Air Dog, Valair Ceramic 12.5", Boost, EGT, Fuel Pressure
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post #9 of 13 (permalink) Old 08-05-2018, 01:10 AM
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With a drop in oil pressure and knocking on a rebuild, one other question comes to mind... do you have fuel diluting your oil? Also, what is your oil pressure at idle and at cruising rpms?

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post #10 of 13 (permalink) Old 08-05-2018, 03:30 PM Thread Starter
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The verdict has arrived. I drained the oil, gathered a sample, and cut open the filter. Today's menu happens to include a decent flaking of bearing material.

Looks like I'm gonna be scheduling time to take the motor back out and send the crank off. I'm gonna go ahead and buy .020 bearings today and have them sent off to poly dyn for coating. Hoping to be back up on the road before
September gets here. Can't describe the heartbreak of having to pull a motor twice in less than a year.

97 2500, NV4500, 4wd. Rebuilt at 400k, .020 over, .010, .010 crank, A1 studs, AFC live, K27, DAP 5x.012, BHAF, 4k gsk, Hamilton 178/208, Air Dog, Valair Ceramic 12.5", Boost, EGT, Fuel Pressure
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post #11 of 13 (permalink) Old 08-05-2018, 07:07 PM
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Quote:
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Can't describe the heartbreak of having to pull a motor twice in less than a year.
I'm with you. I bought a "low mileage" engine from a member when mine had 800k and used a qt of oil every 800 miles. The "low mileage" engine used a qt every 800 miles. I had the original engine rebuilt and 50,000 miles later it was burning a qt every 400 miles, the rings never seated. I had trusted a local machine shop to rebuild it. I bought another engine and rebuilt it myself. So I swapped engines three times in a two year period. Hang in there.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #12 of 13 (permalink) Old 04-17-2019, 10:23 PM Thread Starter
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Time for a long overdue update.

Work got hectic for awhile there. I ended up dragging a job in NC to go to VA for a few months, and basically lost all free time in the exchange of some money. The 97 sat at the house for quite sometime just gathering dust and brewing terrible foresight as the time grew closer to yank the newly trashed a 2nd time motor out of the truck again. I ended up taking a layoff in December, got engaged, and took the next month and a half off work to spend time with my new fiancť as well as catch up on some personal time. I finally made some calls to get back to work and figured, now would be the time to pull the motor. Luckily this time, a family friend who owns a reputable shop down the mountain graciously offered us a bay with a 15k lb 2 post lift to pull the motor and work on the truck as long as we needed. I had the truck towed down to the shop on a Wednesday and proceeded to tear it down Thursday.

Our friend, the shop owner, was pretty excited to see what the heck went wrong with the truck, and basically spent the whole day helping my Dad and I tear the motor out. Let me tell you, itís a lot easier to pull the motor if you drop the transmission and transfer case, and even more so when you have a lift available to you! Within 3 hours, the motor was pulled and we started tearing into it to see what went wrong. After pulling the oil pan off we were greeted by large pieces of bearing material scattered around a glittering sea of oil and metal. Some pieces were as large as my thumbnail, if not bigger. After inspecting all 6 rods and caps, none of the rod bearings spun to everyoneís surprise. The #1 and #7 main were in great shape, however 2-6 were all wiped, with 3 and 4 being the worst of the lots.

Immediately we thought the crank had gotten bent somewhere in the process of machining and install, but the machine shop said the crank was fine. I had my machinist go ahead and balance the whole rotating assembly this go round, from balancer back to the clutch. Everything was within spec up until the pressure plate and clutch were installed and spun. 70grams out of balance, or as Ashley had told me, ďenough to do some serious damageĒ

The crank had to have mains ground another .010, bringing the bearings to a .020 total size over, and the rod journals stayed at .010, and the main bore did need a hone to relieve some of the damage from the large pieces of bearing and rotational mass damage.

I figured while I was here, Iíd send off the p pump to be flow tested, and have the injectors pop tested as well. 3 out of 6 injectors popped bad, and 2 of the bad ones did nothing but leak fuel with a steady drip. The p pump, much to my relief, was functioning just fine.

Flash forward to here now in April, and Iíve been piecing together all the essentials slowly but surely. Upper and lower gasket set with a .010 head gasket, polydyn coated clevite rod bearings, clevite mains, I found new ARP main studs $200, went ahead and bout ARP balancer bolts, flywheel bolts, and rod bolts as well. Iím planning on using billet piston oilers this time round, Iím replacing the oil pressure regulator valve in the oil cooler/filter housing unit, and trying to get DAP to replace the injectors that tested bad with only 6k miles on them for a new set. Iím sure thereís a few other things Iím missing off the top of my head, but itís a start.

Not all is lost with the 97, but damn this thing is expensive!

97 2500, NV4500, 4wd. Rebuilt at 400k, .020 over, .010, .010 crank, A1 studs, AFC live, K27, DAP 5x.012, BHAF, 4k gsk, Hamilton 178/208, Air Dog, Valair Ceramic 12.5", Boost, EGT, Fuel Pressure
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