Z134 Center bearing failure in TO35

I have a spare engine I want to install in the MF50 I got with the rod through the block. The spare engine was in a 1955 TO35 parts tractor I bought and seemed to run pretty well from what I remember except for a rear oil leak so I wanted to fix that first. Once I put it on the stand, I noticed the crank had a lot of end play, so that wasn't a good sign. Once I had the crank out, most of the bearings looked pretty good except the center main, which as you can see in the pictures, isn't pretty. I have blown through all the oil galleys and they appear to be clear and the other bearings didn't seem to suffer from lack of oil. I don't know what the oil pressure was, but the pump appears functional. Any idea why only the center main would disintegrate like this? It feeds oil to the number two and three rods and #2 rod bearing looked good. The #3 rod bearing had some flaking though. There is some bearing metal in the oil hole but not sure if that caused the issue or was the result of the bearing failing for some other reason. I am going to take the crank to the machine shop and see if it can be turned.

Dan

Any history on the engine?

It could have been recently apart and there was a clearance issue with the center bearing.

Or it could have been run out of oil, and that was just the first one to go.

I would also have the main bores in the block checked for size and alignment.

Does that block have the power steering mount hole?

I don't know any history about this engine. I bought the tractor for parts and it ran when I bought it. The cylinders have no ridge at all, I was able to slide the pistons right out so it can't have a lot of hours. The block does have the power steering hole.

Dan

bent crank?

the way the thrust surface is chewed suggests chronic end thrust on the crankshaft - it's unclear to me whether it is the front surface or rear surface that is chewed - possibly either a clutch/input shaft issue or perhaps a bad installation of a pump on the front pulley?

a machine shop should be able to assess the crank, or if you have the block on an engine stand you could install the front and rear bearings and use a dial indicator to measure the concentricity (I think that's the right word) at the middle journal -


David

I agree, sure looks like there was a LOT of thrust against the thrust bearing surface, causing heating.

ok guys educate me. which one is the thrust bearing ?

the flanges on this center bearing serve to limit crankshaft end play - when you push in on the clutch, the crankshaft is pushed forward and the pictured bearing flange rides on the corresponding machined crankshaft surface (lubricated by engine oil) until the clutch is released. I have never seen this amount of mangling/galling/displacement of bearing material associated with the pictured assembly. Something is wrong in the system.

I have seen thrust bearing disintegration on a fresh overhaul when someone holds the clutch down to "make the load on the engine less." As others have suggested, someone riding the clutch could eventually cook the thrust bearing, more so if the oil is low or dirty.

The center main crank bearing is also the thrust bearing.

Thanks, I will make sure to ask the shop to evaluate the crank before doing any work on it. The rear thrust surface was the most damaged so a clutch issue could have been the cause.

Dan

thanks.