Oil leak at rear crank shaft and bushing on Kubota B7100

[r.wagner75]

We recently Replaced the rear main crankshaft seal and gaskets on an old Kubota B7100 and found that it’s still leaking Oil after running for less than 20 minutes.

After splitting the tractor in two again and removing the clutch & flywheel, we’re seeing signs of oil passing between the main shaft and the bushing that rests on the main seal. When I hold a light to the rear end and turn the engine by hand, I notice the outer bushing holds still against the inner edge of the main seal while the shaft occasionally spins in it. Question…..?…… shouldn’t the bushing and shaft turn together?

Should I remove all the bolts and pull the cover again? Can I slide the bushing out without doing a complete tear down?

 

[Russell King]

There may be an o ring between the sleeve and the crankshaft that should have been replaced.

You can look at illustrated parts lists to see if you can locate it or call the parts department of the local dealer and ask them.

 

[r.wagner75]

I’m not getting much help from Kubota and the parts diagram shows another seal but that could be the one that sits inside the shaft for the transmission rod.

 

[Russell King]

My apologies I was thinking that you were leaking at the front of the crankshaft.

After reading again I see that it is the rear of the crankshaft that is leaking.

I believe that @whitetiger or @North Idaho Wolfman would know what to do about that problem.

They may respond here or you could send them a private message asking for help.

 

[Fordtech86]

I don’t know anything about the specific tractor….but have you made sure the crankcase is venting?

 

[r.wagner75]

I don’t know anything about the specific tractor….but have you made sure the crankcase is venting?

Yes I have checked both the vent located in the valve cover and the vent tube. There are no stoppages.

 

[whitetiger]

There is a wear sleeve on the crankshaft which the seal rides on, it sounds like your wear sleeve is loose on the crankshaft.
If you remove the rear main seal housing, the wear sleeve is replaceable and has to be tight on the crankshaft. You should Lock-tite the new sleeve onto the crankshaft.

When installing the new sleeve and not having access to the sleeve installation tool, you can cautiously tap it on using a flat plate until it is flush with the rear of the crankshaft. Then install the flywheel, tightening the bolts a 1/4 turn at a time to properly position it.

Then you remove the flywheel and install a new seal and gaskets.

The small seal over the transmission input shaft pilot bushing only keeps debris out of the bushing.