Near-identical rod bearing wear across different journals after 2000 miles - how?

[Bearman90]

First up, apologies for posting Volvo bearings instead of BMW related, but I was brought here after a Google search to see where I could find people knowledgeable about bearing wear (specifically a topic by deansbimmer )

I had done a bottom-end rebuild after losing my main thrust-bearing, and after a short 2000 miles it seems that it had gone again, leading me to pulling the engine apart again. I noticed some wear on the mains consistent with bad crankshaft work, however I was more confused by the rod bearings. See pictures below:

They seem to have an almost fingerprint-like identical wear pattern across the different conrods. The horizontal stripes appear in the same spaces across different journals. One of the bearings even has the exact same pattern, yet mirrored compared to the others. What could this mean, how does that even occur? Could it be a manufacturing defect of the bearings itself?

These were sets of Glyco Sputtered rod bearings. The shells pictured are the bottom shells that go in the end-caps.

[tdott]

Factory rods? What rod bolts? Were rod bolts installed using a stretch gauge? Were clearances checked? Were crank journals ground / measured? If any of the work was done by a machine shop, your best bet is probably going to be working with them.

[Bearman90]

Maxspeedingrods H-beam rods, ARP 2000 bolts torqued to spec of conrod manufacturer using ARP lube (specifically instructed torque since ARP stretched figures would be too tight, and I do not have a stretch gauge), clearances were checked and crank journals were ground and measured and checked. However, I did not specifically measure the crank towards the sides compared to the middle, unsure if the machine shop did.

The only machine work done this time was on the crank. Backstory is that after ~80.000 miles past my original rebuild with the same setup I began to experience crankwalk - thrust bearing had worn through, and it took the crank thrust surface with it. I thought it was from me cranking the car with my foot on the clutch after installing a heavier pressure plate about 10.000 miles prior, so I just rebuilt the same setup with new bearings and a new crankshaft. I had the crankshaft ground and polished, double-checked measurements myself and installed it using new Glyco mains and Glyco sputter big-ends. It was a bottom-end-only rebuild.

So the only differences compared to the previous setup that was good for 80.000 miles, was a new crankshaft and Glyco bearings instead of OEM Volvo. The thrust-bearing wear can be explained from heavy clutch and failure to think of machining/polishing the crank thrust surface of the new crank.

However, I was shocked to see the state of these big-end bearings after only 2000 miles, so I was wondering if anyone recognizes the pattern. I will contact the shop, but until that time I'm curious as ever to know what causes this wear pattern.

[RocketyMan]

It looks like ALOT of contaminates were in the oil system. Your bearings look absolutely dirty. Also, we're only seeing "half the story" by only seeing half the bearings. The upper bearings might have a different story as well.

If we're seeing wear more towards one side, it would look like something might be bent...like the conrods. But I'm unfamiliar with this engine. Is it a straight 5? Turbo? Anyway...what clearances did you measure everything to? What size are the journals?

Here's a really neat guide that is a great read. I would recommend reviewing it in it's entirety.

https://www.mahle-aftermarket.com/me...s-brochure.pdf

[Bearman90]

I didn't work cleanly taking it apart since the crank is shot anyway so it looks worse than it is, but yes, there were contaminants in the oil which origin's I have traced back to a clear mea-culpa; I made an error in assembling that probably caused a small amount of contaminated oil to be released into the bearings which caused most of that circumferential scuffing.

That being a bit beside the point, I'm wondering specifically how different journals can exhibit a barcode-like identical wear pattern perpendicularly to the circumferential wear-marks. They are profoundly distinct from any regular wear I have seen before and around the internet. Thanks for your resource, I'm reading it as we speak!

I'd happily discuss the post-mortem as well, maybe in another topic or once I found an answer to the above. The bearings that came out after 80.000 miles looked completely pristine compared to this 2000 mile run, and the engine still ran fine apart from the runout issues that made me disassemble.

Edit:

Upper bearings. Sputter coating is completely gone.

[DrFerry]

Originally Posted by Bearman90

I didn't work cleanly taking it apart since the crank is shot anyway so it looks worse than it is, but yes, there were contaminants in the oil which origin's I have traced back to a clear mea-culpa; I made an error in assembling that probably caused a small amount of contaminated oil to be released into the bearings which caused most of that circumferential scuffing. That being a bit beside the point, I'm wondering specifically how different journals can exhibit a barcode-like identical wear pattern perpendicularly to the circumferential wear-marks. They are profoundly distinct from any regular wear I have seen before and around the internet. Thanks for your resource, I'm reading it as we speak! I'd happily discuss the post-mortem as well, maybe in another topic or once I found an answer to the above. The bearings that came out after 80.000 miles looked completely pristine compared to this 2000 mile run, and the engine still ran fine apart from the runout issues that made me disassemble.

Edit: Upper bearings. Sputter coating is completely gone.

I am no deansbimmer but I am a mechanical engineer from GA Tech - for what that's worth. IMO the upper rod bearing shell surfaces are contacting the crank (at the shell edges) probably due to a multitude of factors or a combination of them = A) rod bearing clearances are too tight (probably when hot), B) the oil film is too thin (probably wrong viscosity), C) oil starvation at cold start, D) the bearing shells are too thick compared to the crank resurfacing done (see A). This forum has an Official S65 Rod Bearing Example thread packed full of photos and discussion which is worth studying - linked below. I wish you luck but extra (increased) clearance bearings for your engine may help improve the upper shell, bearing edge wear.
https://www.m3post.com/forums/showthread.php?t=1253084

[Bearman90]

Thanks for the input. I considered A), but the crank was ground down slightly and hence all journals measured in at slightly below stock spec of 50.00mm. If anything, I'd say that would mean clearance was slightly larger. In the previous setup, with stock crank that required no grinding, the same rods put no considerable wear on bearings that ran for 80.000 mi. At B), I ran 5W50 Mobil 1 FS X2, slightly thicker than the first 80.000 mi (0W40) deliberately for reduced wear at cost of slightly worse mileage due to my heavy clutch. I assumed thicker oils had better film strength, but will re-check. C) possible, however again no issues there the 80.000 miles prior so I wouldn't say that's a problem inherent to this engine. D) is possible, I will admit I did not measure inner bore in the rods with just the bearings installed, since they only come in this one size or oversizes anyway. I will measure bearing thickness compared to the OEM Volvo ones.

While I agree any or all of the above might explain the wear on a single bearing, I'm still very puzzled as to why identical patterns were found across multiple journals. Improbable as may be, my thoughts keep falling back to the grinding stone of the machine shop having been out-of-shape causing all the journals to exhibit the same hourglass shape. Especially since the main bearings (all of them) also show wear on the shell edges only.

If all journals were machined to exactly the same deformation, that would explain why the bearings have identical wear patterns, right?

Edit: Your post made me think, and I'm inclined to further investigate A. I've ordered a more precise digital bore gauge and micrometer, and will measure clearance post-mortem.

[deansbimmer]

What Volvo engine? B20?
The outer wear on shells suggest poor crankshaft journal shape.

The “bar code” wear is just a result of the manufacturing process. The wear itself might be caused by a number of things however.

If the journal dimensions changed then the oil pressure may not be able to support the bearing in operation. May be also by how the crank was polished (to what degree and what direction). Poorly polished journals will eat bearings like this.

[Bearman90]

Thanks for your insight, deansbimmer !

It's a B5234T, attaching the pictures I took of the main bearings. Sorry for the bad quality, and upper main bearing #4 picture was a dud. All showed the same pattern though. This is after 2000 miles.

Lower halves 1 through 6:







Upper halves 1 through 6:







Combined with your comments, I'm assuming the polishing job was not optimal. I checked back, and the crank was not ground, it was only polished to remove some light surface rust stains. I guess he had to polish quite a bit which resulted in a bad finish.

I also got my digital micrometers in the mail, so measured mains clearance today. In mm but I will convert. Factory crank mains journals are 65.000 mm, mine all measured in at around 64.988 mm, maximum difference between them being 0.004 mm. (That's 2.5591" factory spec, 2.5586" measured, and a 0.0002" variance between the journals).

I replaced the mains bearings, and installed the intermediate section (the main bearing caps, basically) torqued to spec, then measured oil clearance by zeroing the bore gauge on the micrometer directly after measuring the crank journal.

Factory Volvo specs call for a mains oil clearance of 0.025-0.045mm (0.010-0.018")
Rule-of-thumb wisdom (a thou for every ") says 0.064mm (0.0025")
Mains 6 came in with an oil clearance of 0.078mm (0.0031")
Mains 5 came in with an oil clearance of 0.076mm (0.0030")

So my mains clearance was a bit bigger compared to stock rather than too tight, and I did compensate for this by running 5W50 oil instead of factory 5W40 / 10W40 recommendation. Had no oil pressure issues.

Sidenote for RocketyMan : I just now noticed the mains have considerably less foreign debris marks compared to the big-ends. I assumed I installed dirty bolts through the oil gallery, however it dawned on me that I did not ask anyone to clean the crankshaft oil passages. Hence gunk was probably instantly flushed into the big-ends upon first start.

So I think we can agree it's a combination of bad polishing job for the mains and foreign debris + bad polishing job for the big-ends?

[RocketyMan]

Originally Posted by Bearman90

Thanks for your insight, deansbimmer !

It's a B5234T, attaching the pictures I took of the main bearings. Sorry for the bad quality, and upper main bearing #4 picture was a dud. All showed the same pattern though. This is after 2000 miles.

Lower halves 1 through 6:
Attachment 3662202
Attachment 3662207
Attachment 3662203
Attachment 3662204
Attachment 3662205
Attachment 3662206

Upper halves 1 through 6:
Attachment 3662224
Attachment 3662229
Attachment 3662225
Attachment 3662226
Attachment 3662227
Attachment 3662228

Combined with your comments, I'm assuming the polishing job was not optimal. I checked back, and the crank was not ground, it was only polished to remove some light surface rust stains. I guess he had to polish quite a bit which resulted in a bad finish.

I also got my digital micrometers in the mail, so measured mains clearance today. In mm but I will convert. Factory crank mains journals are 65.000 mm, mine all measured in at around 64.988 mm, maximum difference between them being 0.004 mm. (That's 2.5591" factory spec, 2.5586" measured, and a 0.0002" variance between the journals).

I replaced the mains bearings, and installed the intermediate section (the main bearing caps, basically) torqued to spec, then measured oil clearance by zeroing the bore gauge on the micrometer directly after measuring the crank journal.

Factory Volvo specs call for a mains oil clearance of 0.025-0.045mm (0.010-0.018")
Rule-of-thumb wisdom (a thou for every ") says 0.064mm (0.0025")
Mains 6 came in with an oil clearance of 0.078mm (0.0031")
Mains 5 came in with an oil clearance of 0.076mm (0.0030")

So my mains clearance was a bit bigger compared to stock rather than too tight, and I did compensate for this by running 5W50 oil instead of factory 5W40 / 10W40 recommendation. Had no oil pressure issues.

Sidenote for RocketyMan : I just now noticed the mains have considerably less foreign debris marks compared to the big-ends. I assumed I installed dirty bolts through the oil gallery, however it dawned on me that I did not ask anyone to clean the crankshaft oil passages. Hence gunk was probably instantly flushed into the big-ends upon first start.

So I think we can agree it's a combination of bad polishing job for the mains and foreign debris + bad polishing job for the big-ends?

When you say "polishing of the mains" was this a light sand-paper type of job, or was it on a lathe and ground?

I'm starting to think now all the journals have an "hourglass" sort of wear to them, and come to think of it, the "barcoding" on the bearings might indicate flat spots on the crank.



Can you measure your crank journals from side to side? Maybe too much was taken off in the middle.

https://www.substech.com/dokuwiki/do...ngine_bearings

But yes, your insight of the oil passages in the crank to the big ends being dirty might make sense if they weren't cleaned after the journals were polished. This seems highly plausible.