Farmall M oil Pressure dropoff

scott_mortimer48 · Oct 30, 2009

I recently rebuilt a M motor. It has been sitting for years. I have oil pressure, then about the time the thermostat opens, it begins to decline. If I am working it, the pressure will drop to the border of the red and white on the pressure gauge. I am going to replace the oil pump, and plastigauge the crank bearings. Any other suggestions.

Paul from MI · Oct 30, 2009

Check the oil pump inlet screen?

Goose · Oct 30, 2009

Try a test guage for comparison?

BCnT · Oct 30, 2009

what weight oil you using??? i've had similar problems and 20w50 castrol sure did change things around.

T_Bone · Oct 30, 2009

Hi Scott,

Cam bearings and oil pump are responsible for oil pressure.

A engine builder one time told me that a typical engine only needs 7psi of oil pressure to provide adequate lubrication.

True on todays high-tech engines, I can't tell you.

T_Bone

scott_mortimer48 · Oct 30, 2009

I cleaned the original screen, as well as took the bypass plunger out. It looked like it was hanging up a little inside the sleeve. I am usiong 15-40.

Anonymous-0 · Oct 31, 2009

Worn rod and main bearings will lose pressure as the oil heats up.

John B. · Oct 31, 2009

I would borrow or buy another oil gauge that measures in small increments and see what it says before tearing the engine apart. Like I tell people do the easy tests first.

A new oil pump won"t help much if the cam bearings are worn. My "H" tractor I"m running 0.004" clearence on the rod bearings and my pressure is fine.

The one thing to check is the bottom plate and gasket on the oil pump. This plate gets worn from the pump gears and creates oil bypass or the gasket could be bad causing leakage at the pump itself. If the bottom plate is worn it can be sanded with some sand paper to get the scaring out then reused. I lay a piece of wet/dry sand paper on a very smooth service and put some motor oil on it then move the plate back and forth until the marks are gone. You will have to add oil from time to time during this process.

james rumph · Oct 31, 2009

Food for thought .

When you put the pick up in the oil pump it is a very loose fit that is held with a roll pin.

I went to the hardware and found "o" rings that sliped around the tube and up into the pump.

I also drilled the pump out for the next size roll pin trying to make for a better fit .

The o ring doesn't allow bleed off of oil so my presure is perfect.

Take a look at it ....

Jim

El Toro · Oct 31, 2009

Cam bearings are probably worn. I would use 30wt oil to see it helps the pressure. Hal

rustyfarmall · Oct 31, 2009

I just recently cured a Farmall H with those same symptoms. The Farmall letter series tractors and probably the early numbered series as well are all prone to the same thing. What happens is the cover on the bottom of the oil pump becomes warped, and even though the bolts that hold it on are still good and tight, a gap will open up between the cover and where it mates to the pump, and then the oil, instead of being pumped up into the engine just flows right back out into the oil pan. The cure is to remove the pump from the tractor, and then remove the cover from the pump, and then use some method of re-surfacing that cover so that it is flat once again. I used a large oil stone, others have used a sheet of emery cloth layed down a pane of glass. Of course you will need a new gasket to put it all back together. I made a new gasket, but I think that gasket is still available from Case-IH.
The oil pressure will now peg the guage at start up, and after the engine is fully warmed up, the needle on the guage is still at 3/4 up.

heavy hauler too · Oct 31, 2009

I had one do that, I just pulled the spring out a little , maybe 1/4th inch. Plenty of psi . You only need 10 lbs to the 1000.

heavy hauler too · Oct 31, 2009

I had one do that, I just pulled the spring out a little , maybe 1/4th inch. Plenty of psi . You only need 10 lbs to the 1000.

Farmall M oil Pressure dropoff

scott_mortimer48

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Paul from MI

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Goose

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BCnT

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T_Bone

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scott_mortimer48

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Anonymous-0

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John B.

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james rumph

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El Toro

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rustyfarmall

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heavy hauler too

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heavy hauler too

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