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Mudfly

Farmall M - rear main seal?

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Hey was brush hogging with the M today and I've got engine oil pouring out of the weep hole on the clutch. Probably lost 3-4 quarts of oil while I burned probably 8 gallons of gas.

Anything else to check that could push that much oil into the clutch housing?

Pretty sad when you have to stop more often to put oil in than gas.

If it matters it's a 51 M and pegs the oil pressure gauge at least until it starts running low in oil.

Also that's a split to replace the rear seal right?

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Yeah its splitsville!

Losing oil at that rate makes me worry that your bearing is going out too.

I wouldnt run it at all til its looked into.

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First make sure the crankshaft vents are clear, both the one on the lower side of the engine and the one connected to the air cleaner.

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First make sure the crankshaft vents are clear, both the one on the lower side of the engine and the one connected to the air cleaner.

I'll check the vents but that is what I was afraid of. Where is the vent in the lower engine? Don't know if I knew about that one.

I'll probably check the main bearings when it's split and the oil pan is off. Along with the clutch and trans input bearings. Anything else a person should check/replace while it's split?

I was given this tractor as payment for some work about 7 years ago and haven't put many hours on it. Runs strong but I have no idea what it's history is.

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The main vent is a tube attached to the valve tappet cover near the distributor. It goes down through a clip attached with a bolt that also holds the oil pan on the block. The way the upper vent is attached to the air cleaner tube there is a slight vacuum created in that vent tube when the engine is running. If there is little blowby past the piston rings there will be a bit of air drawn the lower tube and exit out the upper one along with the compression blowby. If there is more blowby than the upper vent can handle the airflow will be reversed in the lower vent and you will see the blowby exiting the engine there. If there is more blowby than can escape through the vents there will be a buildup of pressure in the crankcase. The felt seal on the rear of the crankshaft is not designed to work with any crankcase pressure and will leak oil if there is any.

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Got it. There is some blow by coming out the vent on the distributor side. Would that mean that either the other vent is plugged or that I have a big problem with the rings?

Might be time for an in frame overhaul. See what it looks like inside the engine. Most likely needs rings and bearings. Probably a little work on the valve seats too. I guess you get what you pay for as I got this for basically nothing, that' look like what I got.

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