Determining Bearing Wear

[Bailes1992]

Following on from my troubles with our VW T5 HERE (worth a look if you like blocked oil pick ups from excessive RTV use), I'm currently looking to determine if any serious wear to the engine bearings has occurred.

To confirm, before my strip down, the engine operated perfectly with no abnormal noises. The only reason for the strip down is due to random and intermittent oil pressure lights.

The engine has had an undocumented rebuild at some point in the past, and still uses standard size bearings.

The crank is perfectly smooth with no scratches that can be felt with a nail or anything untoward.

The lower cap bearing seems to have lost it's initial coating in places, but again, is totally smooth with nothing I can feel with my finger nail.

And exactly the same for the upper bearing. Slight coating loss, some scratches but nothing I can feel with a finger nail.

How do I determine if these need to be replaced? I've done some googling and haven't come up with much.

 

[Lubener]

I would use a product called Plasti-Guage to determine the condition of rod and crank bearings.

https://www.plastigaugeusa.com/how.html

 

[ripcord]

To determine if you need to replace bearings, you need to measure the clearances. Like Lubener mentioned, PlastiGuage is an effective way to measure the clearances. There are probably a bazillion videos online about how to properly use PlastiGuage.

 

[Bailes1992]

Cheers guys. I was hoping a visual would have been just fine. I'll order some plastigauge.

 

[JohnB5656]

If possible, change them in place. .001 undersize if needed and available.

 

[Donald]

What about having the crank machined and then matching undersize bearings?

 

[PontiacHO]

If it’s apart already, order a new bearings then check with plastigage. If you need undersized bearings order them. You can mix and undersized bearing with standard if need be.

 

[ka9mnx]

If it’s apart already, order a new bearings then check with plastigage. If you need undersized bearings order them. You can mix and undersized bearing with standard if need be.

Right. If I had it torn down that far it would get a new set of bearings.

 

[PontiacHO]

Right. If I had it torn down that far it would get a new set of bearings.

Maybe I misunderstood your photos…
Looked like the pan was off and a rod bearing cap was off. Bearing halves will roll out with the crank still in the block. The rod bearings as well…

 

[Bailes1992]

What about having the crank machined and then matching undersize bearings?

Right. If I had it torn down that far it would get a new set of bearings.

Answer both questions at once, the engine is still in the van and I need to replace an oil squirter jet. That's the only reason I have one bearing cap off. If this bearing measures up fine then I'll probably leave the rest alone.

 

[MaximumMini]

(Saw the post immediately above just after making this post. You might want to take a look at another journal just to be sure)

Looking at the photos, that crank journal has more damage than you might realize. Any defects will interrupt the designed flow of oil around the journal and through the galleys. To do this right, you need to get more than just the bearing clearances. At the very least that crank needs to be polished professionally. It should also be measured with micrometers for roundness and uniformity.

If all you're going to do is the bearings then at the very least install a new set of bearings (same size).
Just be aware that if there's damage to the crank journals you might still end up with low oil pressure mainly because the main bearings will also have similar wear.

On the flip side, definitely check the the oil pressure with a real gauge not just at start up, but full hot at idle and at 3000 rpm.
It might be everything is ok and you might get many more miles from it. It really is hard to say without full measurements.

Also, did you make absolutely sure that intermittent oil light was indeed the oil pressure using an external oil pressure gauge?
Lots of faults can cause erroneous oil pressure light triggers.
If the light works properly, By the time you see an oil warning light, it's likely some damage has already been done in many cases. Which is the reason I add Oil Pressure gauges to all my vehicles that didn't come with one.

 

[Bailes1992]

Looking at the photos, that crank journal has more damage than you might realize. Any defects will interrupt the designed flow of oil around the journal and through the galleys. To do this right, you need to get more than just the bearing clearances. At the very least that crank needs to be polished professionally. It should also be measured with micrometers for roundness and uniformity.

If all you're going to do is the bearings then at the very least install a new set of bearings (same size).
Just be aware that if there's damage to the crank journals you might still end up with low oil pressure mainly because the main bearings will also have similar wear.

On the flip side, definitely check the the oil pressure with a real gauge not just at start up, but full hot at idle and at 3000 rpm.
It might be everything is ok and you might get many more miles from it. It really is hard to say without full measurements.

Also, did you make absolutely sure that intermittent oil light was indeed the oil pressure using an external oil pressure gauge?
By the time you see an oil warning light, it's likely the damage has already been done in many cases. Which is the reason I add Oil Pressure gauges to all my vehicles that didn't come with one.

Oh, I can assure you the oil pressure issues were down to this...

The crank feels totally smooth. I cannot feel any of those scratches with my finger nail. Actually, I'm not even sure I can see them in person.

 

[Cujet]

The journals can likely be polished. As long as great care is used. The bearings should be replaced. If as you say, the scratches in the crank are not visible, it is quite likely they are minimal in nature. Even so, if you can gently polish out any imperfections, you'll get a great result. A proper journal polish won't change the crank dimensions. Which you can measure with a micrometer.

Remember that the drilled oil passages will fill with polishing agent, so make very sure to cover them. Aluminum tape can work. And then clean them after.

The BMW cars that eat through rod bearings, this is standard procedure. Pull the rod bearings out, gentle polish of the crank journal, clean perfectly, install new bearings with assembly lube on the journal.

 

[SC Maintenance]

As someone who has spent lots of time working on old junk, that bearing doesn't look bad to me. The only wear is on the right of the picture which was caused by something being slightly out of round - either the crank or the rod itself. If you just stick new bearings in without any machining you will likely have the same wear pattern in short order. New bearings can cause their own problems sometimes also. Getting new bearings properly seated in and aligned in the car can be challenging at best.

As for the crank - really cannot judge from a dirty picture. Clean with a brand new terry towel and access the grooves. Those are caused by debris. Unless some are really deep your more concerned with out of round which there is no good way to measure in the car.

If it were mine and I was in the "I want to run this junk as long as possible" mode, I would not take it apart any further based on that single picture. Let sleeping dogs lie. IMHO only.

 

[Marcozi]

Oh, I can assure you the oil pressure issues were down to this...

View attachment 313164

The crank feels totally smooth. I cannot feel any of those scratches with my finger nail. Actually, I'm not even sure I can see them in person.

What is that in the pump????

 

[Bailes1992]

What is that in the pump????

RTV where someone got a big excited when they sealed up the sump last time.

If you click on the link in my first post you'll see the full story.

 

[qvalff8]

I don't have much experience disassembling engines but I'd say everything you found is in good shape or better for the mileage. Nothing catastrophic looking imminent. You haven't seen much speckling of metal in the oil and the engine runs fine. Can you post the oil light trigger pressures/RPMs?

Even if the wear was extreme, you could probably get away with running 10W-60 or something. But I'd out everything back together after the piston squirter is back together. Even that might, just maybe, be optional, but you've already done 80% of the work. Hopefully this'll get you back on the road for another 200k miles!

 

[Trav]

I don't see anything earth shaking, the shiny spots are contact areas from low oil pressure, I assume this is the one with a bad piston squirter? There also seems to be a few particles embedded in the surface? Wipe the crank journal with a lint free microfiber and take a closer look at it, if you cant hang a fingernail on anything there is no issue to worry about as far as surface finish goes, the micro scratches are in the direction of rotation.
Pull another rod cap for a look see, if its the same it is probably from low pressure or even a dry start when it was originally rebuilt. replace the bearings with std size or the sizes on the shells and reassemble with assembly lube. Once you get the squirter sorted out I wouldn't worry about running it, it will probably outlast the body.

I wouldn't get all nancy trying to micro polish the journals, you can make a bigger bugger of things.

 

[TomYoung]

Those rod bearings are not in great shape, even though they may still be within spec as far as wear goes. Your fingernail test does not mean much, and the scores are plain to see. I would prefer the crank surfaces to be mirror smooth, but would definitely measure and replace all bearings, at least while the engine is this far apart.

 

[Brons2]

Oh, I can assure you the oil pressure issues were down to this...

View attachment 313164

The crank feels totally smooth. I cannot feel any of those scratches with my finger nail. Actually, I'm not even sure I can see them in person.

I can only assume the next set of bearings will fare much better without that glob of RTV in the pickup tube. Yikes.

This pic should be required viewing for anyone first learning to rebuild engines, lesson being "less is more" when it comes to RTV.