Broken tooth on oil pump cause bearing failure?

mxracer_nz · Jan 6, 2023

Hi i have an older D41A-3, had #1 rod bearing fail (closest to oil pump). Had a full rebuild 10years ago (done maybe 60 hours) . I did find the oil pump had a broken tooth, would this be the cause of the bearing to fail? would 1 broke tooth make enough difference? i would have though the end bearing would fail 1st if starved of oil?

Coaldust · Jan 6, 2023

The HEF loves failure analysis. Post of picture of the rod bearings so we can determine why it failed.

If the oil pump is the culprit, you are going to see issues with all the bearings. Am curious why the oil pump is missing a tooth.

mxracer_nz · Jan 6, 2023

Hey have attached some pics i only had 1st ones of mains, and the last 1x of rod ( they all look similar to this one) the 1st bearing had completely disappeared so assuming alot of this damage was bits of bearing going through everything? the damaged tooth was just floating in the pump. there was no signs of other damage in pump.

kshansen · Jan 6, 2023

Any chance of some pictures of the oil pump gear and housing?

Coaldust · Jan 6, 2023

I see the one failed rod bearing with heavy side wear, well into the copper. I would like to see the back side of that shell . It shows the indications of a bent rod.

Why is the rod bent? Incorrect timing, use of starting fluid, incorrect fuel setting?.

There is contamination damage on the mains, but that’s not the root cause of failure. I feel like I’m overlooking something. I’ll have to ponder this some more.

I would cut open the lube filter, for grins. Are the rods drilled?

kshansen · Jan 6, 2023

Coaldust said:
I see the one failed rod bearing with heavy side wear, well into the copper. I would like to see the back side of that shell . It shows the indications of a bent rod.

Are you referring to this picture?

I think those are main beating lowers, as there a seven of them.

Coaldust · Jan 6, 2023

But there is no oil groove or hole.

Nige · Jan 6, 2023

Coaldust said:
But there is no oil groove or hole.

See the other photo of the upper (block side) of the seven main shells. I'm assuming here that the photo KSH posted above was of the cap main shells.

mekanik · Jan 6, 2023

Is the bearing with the heavy wear the rear?

Coaldust · Jan 6, 2023

The Op said it was #1. I’m wondering if the #1 rod journal is ground under size with a standard bearing installed. Perhaps a lack of lubrication on that particular journal.

Nige · Jan 6, 2023

Has that engine ever had anti-freeze in the oil for whatever reason.?

Coaldust said:
The Op said it was #1. I’m wondering if the #1 rod journal is ground under size with a standard bearing installed. Perhaps a lack of lubrication on that particular journal.

Time to take a look on the back of the bearing shells and break out the micrometer for the crank.?

John C. · Jan 6, 2023

What is the make and model of the engine? Damaged bearings is only one piece of evidence in a failure analysis. One would need to examine all the the components before trying to deduce the root cause of the failure.
Some other questions, is this the rebuilt engine we are talking about or the original engine. Sixty hours of operation is nothing in the projected life of any diesel engine. One should probably do some measurements of the components and look into the history of what was done by the rebuilder. Were new rod bolts installed? Was the crank polished or ground? Was the oil pump new or jest reused?
Another thought, just because the oil pump is mounted next to the front bearings doesn't mean that the input wasn't plumbed to some other place. Many times the input oil goes to the middle main bearing and then flows to the rest.

Nige · Jan 6, 2023

John C. said:
Another thought, just because the oil pump is mounted next to the front bearings doesn't mean that the input wasn't plumbed to some other place. Often times the oil goes to first to the centre main bearing and then flows to the rest.

I agree. Before you posted I was about to ask on which journal was the oil feed to the crank, expecting the answer to be #4 main journal. TBH the location of the oil pump doesn't make a lot of difference in the grand scheme of thing when the oil goes from the pump outlet to the filter and from the filter to the engine.

92U 3406 · Jan 6, 2023

Which gear? Drive gear or one of the gears in the pump?

If the pump wasn't turning, everything would be cooked, not just one bearing.

mxracer_nz · Jan 6, 2023

Hey thanks for replys

Motor is a Komatsu 6d105. After closer look at motor, the oil pump is at front on motor, but oil filter is on the very back end of motor, it looks like oil galley goes to back end 1st (would that explain 1st bearing fail as least oil getting there?) that copper coloured bearing is at the rear. i will attach pic of broken pump

engine was rebuilt after seizing (we had 15 years of use before seizing) the shop that rebuilt it is a well know one, although we got quoted approx $10,000 (NZD) then they gave us a bill of $24,900, we fought the price down to i believe around $20k. i wouldn't think they done us dodge and put old parts back in after them but who knows. Just looking at repair bill it Had used crank ground and .050 bearings. new oil pump fitted.

no engine start been used. I cut oil filter was just really black but no pieces of debris of any sought. no antifreeze been in oil, hasnt used any fluids since rebuild was running great. (re john c this is all on rebuilt engine, and they charged for new rod bolts)

i have attached new pics of sets of mains and conrod bearing front and back

mxracer_nz · Jan 6, 2023

pump and gears

John C. · Jan 6, 2023

The front rod bearing is the usual damage place that shows up from lack of oil generally on most Komatsu engines that I've put my hands into. Photos of the broken sides of the oil pump gear might tell a story. Was there a suction screen on the uptake for that pump. A broken tooth initially indicates a foreign object got in there to break the tooth. It could also be a bad gear to begin with. Photos of the outer case might reveal scratches and gouges from foreign objects or the broken tooth itself. Was that broken tooth recovered? The way the teeth are engaged doesn't reveal anything about possible back lash between the gears themselves.

Coaldust · Jan 7, 2023

Okay. So, did she start knocking? What prompted the disassembly? Or, did I miss that?

epirbalex · Jan 7, 2023

mxracer_nz said:
Hi i have an older D41A-3, had #1 rod bearing fail (closest to oil pump). Had a full rebuild 10years ago (done maybe 60 hours) . I did find the oil pump had a broken tooth, would this be the cause of the bearing to fail? would 1 broke tooth make enough difference? i would have though the end bearing would fail 1st if starved of oil?

You could have used your 2021 thread or is this a different motor thats had the same problem . Last time there was no oil pressure at one point

mitch504 · Jan 7, 2023

epirbalex said:
You could have used your 2021 thread or is this a different motor thats had the same problem . Last time there was no oil pressure at one point

https://www.heavyequipmentforums.co...or-motor-rattle-with-video.89235/#post-987377

Broken tooth on oil pump cause bearing failure?

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