Hi,

1998 Tacoma V6 250k miles. I blew a headgasket and repaired that including valve job. Then about 1000 miles later, got a slight rod knock at 2500 rpms at very light load. I believe its because I drove it too long with bad HG and on the last start the starter got partially stuck and damaged bearing. Oil pressured verified shortly after HG repair and it was fine. I have pulled pan and verified same cyl that blew HG has a bad rod bearing, engine still in truck. No piston pin play that I can detect.

The crank journal does not look bad, some light scoring but fingernail does not catch on it. I spent about an hour using 800 grit sandpaper on the journal using the shoelace method and its much better, cant feel anything with my fingernail but if I shine a light at a steep angle I can still see the scoring. I'm thinking I should drop to 400 grit but I'm concerned about clearance.Of course I will run up to 2000 grit + polish.

My rod has a number 2 on it, I assume this means my OE bearing is Mark 2? I don't see a 2 on the bearing like FSM says but I see a part number. That means I could go to a mark 3 if I have to but difference is only +0.0001? Why would they even bother or is this a misprint? Or is wall thickness delta not the same as clearance delta?

So I'm wondering what is typical OE rod bearing clearance? FSM says up to 0.003 is OK I'm guessing they start low since min 0.0009 then I should be OK even if I end up removing 0.0005 or so but I don't have experience with this so I'm wondering how good the journal should be vs danger of removing too much material and not meeting clearance.

I have not removed a good rod cap to see what a high mileage bearing/journal looks like - are they pristine assuming engine well taken care of?

Ordering new bearings today, Mark 2 and Mark 3 and I have Plastigauge.

Thanks for any advice.

Thanks

 

I was not aware that Toyota offered the selective fit standard bearing shells for service.

Please let us know if you are actually able to source these shells.

 

They are listed on online parts catalog but the dimensions dont really make sense to me. Perhaps mainly for obsessive factory build Toyota tolerances.
Anyhow I think I'll be OK, from what I can tell if scoring is light to clear it up is just on the order of 0.0005 or so.
I started with 800 grit because i figured I could not do much damage given my lack of experience. I'll probably do a bit more with 800 grit then continue with finer grits.

 

Have you talked to the folks at a machine shop? When I was building my 22RE I had some parts questions and brought my catalogs and notebook with measurements in. They walked me thru what I needed to order. In that case I had them put together my rotating assembly because it was worth it for my schedule so they made money on me even with taking the time to explain.

You may have to pay a small consulting fee if you are doing all the work yourself.

 

What do you mean the starter got stuck and damaged a bearing? Are you sure you didn't hydro lock that cylinder and bend the rod?

When I was a field service mechanic at a Caterpillar dealer, we used to roll in bearings on the machines when needed. A little scoring is ok. You don't want deep scoring or high spots. We just used strips of scotch brite type stuff ( I don't remember the actual name.) to polish up the journals and knock down any high spots. Just a few strokes like you described. Nothing took an hour. You better mic the journals if you can. At least check it 90 degrees apart to make sure it's still round. You're going to have to install a bearing and at least Plastigauge it to see where you're at.

It doesn't have to be "perfect" but you need to be within tolerance. Not too tight or too loose. No gouges.

Good luck with your repair. I hope it works out for you.