D4 7U Rear Main Seal

No rear main seal, just close tolerances so the big reverse screw thread on the crankshaft brings oil back and dumps it into a channel behind the actual bearing area with a drain to the sump. Sounds like your bearing clearances are probably at max wear thus opening up the screw thread area which allows oil to leak. I think there was a kit to add a lip seal type rear main seal for tractors operating on inclines where oil transfer was a problem. I have never seen one but it has been discussed on here before.

Hi Team,
as CCJ says there is no positive oil seal at the rear of the crank--just an oil scroll.

First thing to check is the condition of the crankcase breather filter screens-- in the canister on top of the oil filler elbow.
If this clogs then any engine blow by flow can build up pressure in the crankcase and force oil out thru the scroll into the clutch compartment--keeping this screen clean is important for this reason.

As well as worn main bearings changing the designed gap around the crank and its bearing bore, the drain back drilling mentioned can clog with oil sludge if maintenance has been neglected. Other leakage path can be via a compressed packing between the rear main bearing cap and the cylinder block--usually shows soon after being put into service if the packing has not been installed correctly and tightly packed--fiber packing string similar to pump packing etc.

The machine Maintenance Instruction says to wash and oil the breather screens every 250 hours of operation or I would recommend to do this more often in dusty conditions.

Hope this helps.
Cheers,
Eddie B.

The crank case filter is clean and not filled with dirt. The dozer has been sitting for a while before I got it, so it has not been apart in quite some time (if ever). I am thinking the drain passage could be blocked from the responses so far or maybe the packing has worn down? Can anyone tell me if the drain in the main bearing back to the sump is accessible with the engine in place by removing the oil pan?

Thanks

I know this may be a long shot but can someone show me where this, what I have in () located.
Please and thanks. Ive been working on this d4 with my husbandand im confusedon where this screw is locate. (bearing clearances are probably at max wear thus opening up the screw thread area which allows oil to leak. I think there was a kit to add a lip seal type rear main seal for tractors operating on inclines where oil transfer was a problem)

I know this may be a long shot but can someone show me where this, what I have in () located.
Please and thanks. Ive been working on this d4 with my husbandand im confusedon where this screw is locate. (bearing clearances are probably at max wear thus opening up the screw thread area which allows oil to leak. I think there was a kit to add a lip seal type rear main seal for tractors operating on inclines where oil transfer was a problem)