spun rod bearing (D7 17A)

[quote="dd8hunt111"]It's been awhile since I've been on this site. for several months now I've been having too much fun running the old 17A,but with great sadness i must report
i have damaged the jewel severly😞 .I was cleaning out a small stream last week when i suddenly heard a loud knock in the engine, i let the engine run for a few minutes at slow idle in case it was a water knock.I removed the front panel and could move #2 rod up probably 1/2 inch, the bearing was in small peaces at the bottom of the oil pan.
The engine had been rebuilt less than 400 hrs ago!!!! The previous owner said that #2 rod had been knocking on him, so he removed the engine and did a complete rebuild.
I'm not sure as to what extent i need to tear down and rebuild.I assume the entire engine.Any guidance appreciated
thanks
don[/quote]

this wouldn't be the first time that an engine has been overhauled and the crank not cleaned out properly, I'm afraid its a complete strip to fix the crank and clean it right out.

It sounds like someone did a pretty poor job of overhaul by way of either not grinding the crank when it needed it, or leaving trash in an oil gallery from a previous engine failure, as Catsilver outlined.

My middle nephew blew the motor in his D9L early last year (340😎 and he acquired a fully remanufactured, guaranteed, 3408 engine from an independent engine rebuild shop.

It took the fitters 3 days to get the old engine out, and the new one in and all buttoned up (the hightracks aren't the best tractor to get engines in and out of).
They hit the starter, and it ran for 30 seconds and seized solid. Someone never cleaned trash out of an oil gallery and it went through all the bearings.

The fitters were cursing the reconditioners for giving them another 3 days work they didn't need .. and the nephew was in a flat spin trying to find another engine quickly .. but I'd hate to think how much that engine rebuild shop lost on the deal. All because of a lack of care and thoroughness in the rebuild.

Your D7 17A engine will need to come right out, and be rebuilt properly, with attention to detail such as crankshaft condition, and cleaning. There's no shortcuts on Cat diesels if you want to get satisfactory life from a rebuild.

Hi Team,
as others have said the oil passages are to be scrubbed out with propper fitting gallery brushes available in the Cat system for the purpose. Cooked in oil sludge and metal particles.
From memory most of the older big bore engines also have lightening holes/sludge traps drilled into the bigend journal. In the days before good lube filtration these were essential to catch crud and help prevent premature bearing failure from contaminated lube oil.
Once the traps have filled with sludge further sludge then passes thru the bearings with detrimental results which lead to a bearing failure. If the failure is caught early enough and a new bearing is fitted it is just a matter of a short time before the next failure occurs, this scenario will continue until the traps are cleaned out and refill!!!!!
The traps have about a 1 3/4" dia. welch plug held in with a difficult to remove circlip.
Hope this helps.
Cheers,
Eddie B.

Hi edB,
Seems odd that neither the service manual or parts manuals for the 17A make mention of these plugs!!! What gives??

Cat still uses these plugs on the 3508,12's,and 16's. I pull them on tear down and keep in my tool box so when the crank arrives back from the machine shop i can inspect to see if the cleaned them or not. I've found several they missed in the past.

Half an inch !!! That must mean the con rod or the crank is severely worn, surely it would have given plenty of warning berfore getting that bad. I think those caps are just blanks over drill/machning access points. You should not get any degree of sludge build up in a crankshaft especially if servicing is to schedule.

I would be more inclined to believe this was an assembly problem....probably a shortcut in the rebuild process. Those bearings are substantial with dowel location, not the tabs of later units. I would suspect the crank was not turned when it was supposed to, dowel heights were not observed, clearances were not correct, possibly loose or improperly torqued rod bolts. Oil filtration is generous on the D339 and bearings will tolerate a fair amount of abrasion. Contamination from drilled passages or sludge traps would be my least suspect.
It's a shame that no one listened to the engine talking of a rod knock.

Thanks to all for there input.I suppose their are lots of things that could have been missed in the rebuild that caused the failure.I somewhat thought the same thing as OM.The previous owner told me that he did the following rebuild on the engine:reconditioned heads,ground .010"-.020" on #2 rod journal,replaced rings,main and rod bearings and honed the cylinders(did not replace the sleeves).the work was done in a metal fab./tool shop that he was part owner .I thought he would have paid close attention to all the specs since he is a retired tool maker.He also told me that second gear was grinding
and he replaced it,i only ran in first gear when i tried out the machine.I don't know how he replaced 2nd gear since i have never been able to find it !!!! (could there be an adjustment that would cause this or maybe it was never fixed just blocked off)?It's like hitting a brick wall.For me this was cause to be concern.I guess I'll know to what extent the rebuild was when i get everything torn down.
Sorry guys for getting so long winded, I think lesson learned is when you look at something to buy take someone with you that knows where 2nd gear is.😄
Thanks again guys for listening
Don

Anyone who grinds just ONE journal, is a "shortcut merchant" who is doing repairs "on the cheap". It's pretty obvious that the engine repair was never done properly or thoroughly, and that shows in the repeat engine failure at 400 hrs after "overhaul".

A properly carried out engine overhaul involves stripping the the entire engine, careful examination, measurement and cleaning of ALL components, and machining, grinding and component replacement, where those components are "out of spec".

If any grinding is carried out, all journals should be ground to the same dimensions. Block tunnels need to be checked for alignment, and machined if needed .. conrods checked for cracks, straightness, big & little end alignment, center-to-center dimensions, ovality, bearing shell fit, and even weight. Variations in conrod weight make for imbalance and vibration. Flywheel runout is a measurement that is often overlooked, but which is vital.
Crankshafts need to be crack-tested, and checked for bends, and straightened if needed. Correct radiuses at the edge of journals are critical to avoid crankshaft failure.

The list is long and extensive, but a proper engine overhaul isn't cheap, and the life you get from an overhaul is relative to the effort put into it. I stole the local Cummins dealer top mechanic, one time .. and in the time that he worked for me, rebuilding my Cummins', Macks, and Cats, it was a real eye-opening experience.

This guy measured everything, cleaned everything perfectly, and missed nothing. He was such a perfectionist, that I watched him go through about 20 Mack "reconditioned" conrods one time, that had been supplied by an outside reconditioner .. just to get 8 that matched his demands for perfect specifications.
He pointed out that 12 of the 20 "reconditioned" conrods were borderline on specifications, and some didn't even meet the specs.
Anytime he rebuilt an engine, it was a certainty that that engine would start and perform like a new one, and would run 12,000 hrs minimum without stopping.