Big end bearing smashed can I just replace bearing?

[RR76]

So one BEB has totally smashed. Now from what I can make out both the rod and crankshaft will be damaged but not necessarily (that seems to be hopeful thinking though)

If I replaced just the bearing what's the best and worst case scenarios?

[bearman68]

Why has the bearing failed. That's not normal.

[RR76]

Car was run with no oil, no warning lights and I was told it had been topped recently.

[bearman68]

Scrap the engine, unless it's something rare or very expensive.

No oil to the extent that a bearing has failed will cause issues everywhere in due course.

Ask me how I know.

[RR76]

Ok I do believe you but I'm very pi***d off at myself for letting this happen.

I already have the cylinder head off. All I need to do is remove sump and pop out the piston.

So if I did just replace the bearing can you describe what would happen, would it just bust up right away?

I've heard you can use Emory cloth to polish the crank?

Could I see it as an experiment or a hard lesson to learn sort of thing?

I'm not taking the crankshaft out, the head was enough and I'm not removing the gearbox, clutch, flywheel and the rest, that's just too much for what it's worth.

[Happy Jim]

Best - you get away with it.
Worst - you chew up the rest of the engine

If it’s not worth “doing properly” then you don’t actually have a worst case, you just get back to where you are now at worst.

Jim

[bearman68]

RR76 said:

Ok I do believe you but I'm very pi***d off at myself for letting this happen.

I already have the cylinder head off. All I need to do is remove sump and pop out the piston.

So if I did just replace the bearing can you describe what would happen, would it just bust up right away?

I've heard you can use Emory cloth to polish the crank?

Could I see it as an experiment or a hard lesson to learn sort of thing?

I'm not taking the crankshaft out, the head was enough and I'm not removing the gearbox, clutch, flywheel and the rest, that's just too much for what it's worth.

I replaced the cam shaft journals on an A3 quite a long time ago, I had the head off, skimmed the head, replaced various valves, replaced head bearings etc etc. After getting the engine to run, a short time later, it snapped the new cam belt due to bearing failure in the cam shaft. I would have been better spending the money on coke and hookers. At least it wouldn't have been wasted.
There's a decent chance you'll do the same with your engine.
Be very very careful about using abrasive materilas on the crank - I suppose it would be possible to remove any 'pick up' on the crank journals, but it's a very fraught thing to do.

[RR76]

Happy Jim said:

Best - you get away with it.
Worst - you chew up the rest of the engine

If it’s not worth “doing properly” then you don’t actually have a worst case, you just get back to where you are now at worst.

Jim

So will the crank journal be bent, scratched or what and if just scratched why is that a big deal. I get it's precision engineering but you'd think a few scratches wouldn't matter. Now if the journal/crank is bent then I can see how your at least get a loss of power and at most drive the piston olinto the wall or just leave more play between piston and connecting rod and journal which over time would smash the bearing again. Have I got this right?

What exactly are the scenarios in a detailed way?

[Evoluzione]

Take it to someone who knows what they're doing or stick it on Ebay as is.

[RR76]

Evoluzione said:

Take it to someone who knows what they're doing or stick it on Ebay as is.

It's not worth it, it will cost a lot.

[normalbloke]

What vehicle/engine is it? Pulling a big end cap and looking at the journal will give you the best clue.

[steveo3002]

how do you know its smashed if the sump is still on?

pretty much any mark on the crank will ruin a new bearing ...if parts are cheap and the crank is nice then no harm giving it a try

[RR76]

steveo3002 said:

how do you know its smashed if the sump is still on?

pretty much any mark on the crank will ruin a new bearing ...if parts are cheap and the crank is nice then no harm giving it a try

I took a recording of it and have been told it's rod knock that all makes sense as I've looked at cam/valve train and it all looks good. I'm 100% sure it's a busted bearing.

Could I try the Emory cloth trick to polish the crank if it does just have scratches?

I'll take off sump today and look then post pictures later on.

[bearman68]

Good idea.

Polish the crank really well, ideally with some 80 grit emery. Use progressively finer grit until you get to about 180.

Let us all know how it goes. I'll watch with interest.

[DVandrews]

If you want to remove any pickup from the crank use P1200 wet/dry and a lubricant such as WD40, if the rod of journal are blued or hammered in any way or if the bearing backing has smeared out over the rod then scrap the rod and crank as a minimum.

[Turkish91]

bearman68 said:

Good idea.

Polish the crank really well, ideally with some 80 grit emery. Use progressively finer grit until you get to about 180.

Let us all know how it goes. I'll watch with interest.

180 grit as the final finish?! It’s a crankshaft not a polyfillered stud wall

OP what car/engine is it? There’s no way you can tell for sure it’s rod knock without opening it up fully, let alone on just the one rod. If it’s been starved of oil, all of the crankshaft bearings will have got hot, regardless if only one has actually spun as you seem to think.

Modern & high performance engine crankshafts are quite often hardened/coated so re-cutting/polishing and using oversized bearings often doesn’t work for long. I had this with my Evo 6 - was advised by several engine builders not to bothered trying to save my original crank and just chuck a new one in.

[stuthemong]

DVandrews said:

If you want to remove any pickup from the crank use P1200 wet/dry and a lubricant such as WD40, if the rod of journal are blued or hammered in any way or if the bearing backing has smeared out over the rod then scrap the rod and crank as a minimum.

Listen to this man above all others. He's a very experienced engine builder.

[RR76]

Ok so I took sump off and find a bent scored slightly mangled piston bolt in the sump pan, I also find very thin shards of metal, they are like plastic, maybe 0.5cm^2 at most. It's hard to tell if they are from the bearing or something else could even be from the piston bolt.

As if happens a ex mechanic came up to me while I was looking at this bolt, he said right away that's a piston bolt and your engine is totally screwed just by looking at the bolt. I kind of new right at the beginning that the engine was finished.

So what do you think, I assume I can't just replace a piston?

I've pretty much given up and am going to call salvage yard tomorrow to pick it up, it was a throwaway car anyway.

Opinions?

[gazza285]

[steveo3002]

good chance its dead or uneconomical repair

pics of the bolt arent helping...need to see what the crank and bore look like , then has the swarf gotten into the pump /oilways

prob easiest to look around for a used engine tbh