Rod bearings, failure mode

[ah1955]

Bjorn
Was just thinking here after reading your post, did you get an oil sample.
Higher readings in metals(copper,brass) would be a sure sign of a bearing desinagrating.

 

[cranetruck]

Yes I did, it was posted in a different thread, but here it is.

 

[cranetruck]

From a previous analysis report, the Lead was only 13 ppm and copper 9. The iron was higher before at 104 ppm.

According to the report sheet, Lead is an overlay on the bearings, so they are wearing (obviously).

 

[derby]

Hope I am adding info to the thread and not stealing it.I pulled the pan today found metal in the drain plug,pan was clean.There was some blueing on the crank main and rod journals,is this from hardening or overheating? also a tip, it looks to be easier to remove the pickup tube to pull the pan.This will save the rubics cube of removing it.

 

[cranetruck]

Did those bits and pieces collect since your last oil change?

I can see that I'm in for a big job. Gotta start to think like Leonard Jones.....

 

[JasonS]

I believe that the blueing is normal for the heat treating process.

 

[OPCOM]

ouch.. but looks like you caught it in time.

 

[derby]

Cranetruck,This is a replacement engine out of another truck I had.the oil had ben drained by the DRMO before I got it,so I had no idea of it's condition.I only hear a slight knock in the engine at start up once oil pressure builds it is gone.that and the presence of shavings in the filter led me to pull the pan.I do not see any shards or any odd coloring at the journals and the cam shaft looks ok.I will pull some rod caps in a day or two and post results.there is not as much room as I thought there would be!

 

[Recovry4x4]

it might be easier to remove the entire front differential

 

[FreightTrain]

Pull a cap and look at the bearings.You can pull them and retorque them down if they are ok without screwing anything up.We do this all the time for race engines that get way more abuse than a Multifuel ever thought about.

 

[WillWagner]

A spun bearing turns the cap, a main or rod, black. And, the oil gets baked on the cap making it look bubbled and rough. Also, you will usually see a bunch of jaggad edges poking out from the sides of the cap. Also, the material in the pan will have a "squished out" look to it. The blue color is normal heat treating colors, but, most of the time, just the rod and main journals are treated, not the caps. The bottom end looks good!

 

[jesse poundstone]

Hey i have been a diesel/ heavy equip. mechanic for 5 years i ve heard alot of "rod knocks" in my time. truth is diesels run very loose tolerances to help cope with the extreme heat of operating at full power and torque. all diesels will clank and rattle when cool they are designed to make horsepower and the internals are machined to meet the correct clearances at running temp/full horsepower not when cool and at idle thats why they rattle oil pressure,that means nothing all engines will be different with the different oil viscositys and hours on the engine even what your valve lash is set at all affect oil pressure. the only way to tell if you for sure have a rod bearing going out is to cut the filter open and sqeeze the oil out of the pleats then pull the pleats open and look for metal pieces if the re some metal pieces pull your oil pan and spin in new rod bearings and main bearings just be sure to measure or match up the part#s on the bearings to make sure the new ones are not over sized also use lots of assembly lube torque every thing up and burn.

 

[Lawrence of Arabia]

I have one that is knocking after overheating the engine. I am going to drop the pan and check out the damage. I am hoping I can slip a new bearing in. However I worked in a machine shop and built many engines over the years and I am sure it won't be that easy.

 

[saddamsnightmare]

September 12th, 2009.

Cranetruck:

I'd pull the oil pan, check the bearings and caps, and rebuild whatever shows wear, because that will cost you less the a catastrophic failure. The one thing most people overlook, is the mass of the rotating components in these large diesel engines.... when they fail it can get real exciting. You should have seen what happened when an ALCO 251 engine in an 1800 HP locomotive went due to lube failure.... it was very INTERESTING to watch 16 104+ pound piston rod & big end assemblies go out the side and roof of the engine room.......at about 800 RPM when they went! (the whole engine without generator set weighed about 17 tons).

Of course, if your engine blows up, you can always get another in the can, and maybe upgrade!
Cheers,
Kyle F. McGrogan

 

[Parker2]

This thread is from 2007. I hope he's done something about the knock by now.

 

[Rattlewagon]

Yea, this one has been around for a while....

Bjorn, what was the outcome?

 

[OKCMoparGuy]

On gas engines and common rail diesels you can do an injector kill test (electrically disable the injector) to isolate a rod bearing or wrist pin. With no combustion pressure sometimes the knock will go away. Never done it on a diesel with nozzles but you could probably just disconnect the fuel line on that cylinder, redirect the fuel to a catch can and start the engine. There won't be hardly any pressure coming out since there's no resistance to flow.

Another thing to think about with low oil pressure is the locating of the sending unit on the block. Don't have my duece yet (waiting for EUC to clear) but if the sender is in the front of the block the oil pressure at #6 could be even lower than the guage indicates. If theres access to the oiling system on the back of the engine you could verify with a manual guage.

 

[cranetruck]

Yea, this one has been around for a while....

Bjorn, what was the outcome?

The deuce has only been used around the yard since returning from OK with the 8x8 in tow. The "knock" is of concern, I may be a bit paranoid about it and all the people that has listened to it more or less just shrugs it off.
The low oil pressure IS an indicator of something not being quite right, so when priorities shift back away from the 8x8, something will be done...give me another year or two...

 

[Boatcarpenter]

Bjorn,
Have you purchased your rod bearings yet? If you have, I know you scout out the best prices on stuff so I was wondering where you got them.
BC

 

[jimk]

If you find a spun bearing this won't matter as you'll be getting a re-grind w/ new bearings or new engine - Anyways, the bearing needs to be a bit bigger than big end/main hole for crush fit. A coarse finish and assy w/o oil on back side(s) bearing shells is also a good idea