spin a bearing on crankshaft

[dchilton]

If you spin a bearing on your crank and the crank is still good could you just replace the bearing? As long as the clearance check good. It is on a 90 horse diesel tractor. Thank you

 

[Snobdds]

Yes, it's possible to roll in a new bearing. However, I would find why the oil pressure was low on that cylinder first. I would pull the oil pump and have a look, see if any thing is not right.

 

[dfkrug]

If you spin a bearing on your crank and the crank is still good could you just replace
the bearing? As long as the clearance check good.

I recently completed a rebuild of an old Goldwing with exactly that problem. Sadly, the spun bearing
eroded some of the steel off the crank journal and increased the clearance. So I had to replace the
crank. If it had been in spec, I would have reused the crank with the new bearing inserts that I bought.

 

[RickB]

I admire your optimism.
Yes, it is possible.

 

[paulfun9]

Its very rare that I would take a chance on a simple replacement of the bearing without the very least a polish of all the surfaces in the shop. In most cases I would have the crank cut and resurfaced and buy the appropriate bearings for the new measurement. That's why they make so many different size bearing for almost all engines, a cut and polish cost almost nothing compared to most cranks.

 

[redman135]

My MF135 partially spun a main end bearing. The engine was shut down before seizing.
The crank was pulled cleaned and polished and refitted.
I replaced the full set of bearing shells, new piston rings and a full set of gaskets and seals and put the engine back togather as I had very little money at that time.
It had done about 5000 hrs before the tractor was sold.
Good luck with yours.

 

[jaydee325]

I'd be concerned about the condition of the block journal.

One engine I rebuilt with a spun main had to be sent to the machine shop for an align bore. It was that chewed up!

 

[jimmysisson]

Try it with Plastigage first, and think pessimistically when doing so.
Jim

 

[crazyal]

I had an old Toyota pickup that was used mainly for playing in the mud. It started making a light knocking noise so I pulled the oil pan (since it was lifted with large mud tires I could do it without remove the engine). The bearing partially spun but didn't damage the crank. I replaced it. It measured within range using plastic gauge and since I really didn't care too much about the engine I tried it. It ran for maybe 6 more months until I pushed the engine pretty hard while playing in the mud (those 2.4L 4 bangers didn't like to spin 38" super swampers) and it spun again. By the time I got it out of the mud the crank was shot. The engine didn't have great oil pressure to begin with so I wasn't surprised. I could have tried some motor oil honey to help keep raise the pressure but at the end of the day the bearing spun for a reason. Unless you resolve the reason it'll most likely spin again. In my case I would of had to replace all the bearings and probably more. So if you do it do I would do all of them and maybe replace the oil pump if it's in the oil pan and easy to get at.

 

[buickanddeere]

As previously stated, the concern is the condition of the mating surface between the back of the bearing shell and the block/main bearing cap.

It could cost less now to perform an proper rebuild vs rolling in a bearing then having the new bearing spin and tear the block and cap up.