Ford 8n low oil pressure

Midwest farmer · Dec 9, 2021

Alright yall working on an 8n ford here and right now were only getting 10lbs of oil pressure at full throttle. Weve rebuilt the oil the pump with good gears inside and the gasket was put on right without torque specs. We didnt use silicone and also primed the system as stated in the manual. Really stuck here where we should go next before we tear it down again. Any help would be appreciated! Thank you!

Janicholson · Dec 9, 2021

Four things: is the gauge accurate? Have you checked bearing clearances on the rod and mains, and is the oil pressure relief valve
operating correctly? and are you using a multi wt. oil like 15-40? Jim

Midwest farmer · Dec 10, 2021

The gauge is functioning and accurate and we have not checked the bearing clearances on rods and mains and also where is the oil pressure relief valve located. And we are using 15-40 harvest king oil.

Four things: is the gauge accurate? Have you checked bearing clearances on the rod and mains, and is the oil pressure relief valve
operating correctly? and are you using a multi wt. oil like 15-40? Jim

grandpa Love · Dec 10, 2021

Full throttle, hot motor? If so I
wouldn't worry too much. Most old N
tractors have low oil pressure.

Fritz Maurer · Dec 10, 2021

Take this out and see if the spring is broken, or crud
under the valve so it cant close. But my gut feeling
is that you wont find anything wrong here. Sure is
worth a try though.

Steve@Advance · Dec 10, 2021

Most likely excess bearing clearance.

But unless the pressure has suddenly dropped and/or there is knocking, it may run a long time like that.

If you go into the relief valve,it's a common myth that stretching or shimming the spring will raise the pressure. It won't. Only if the spring is broken or the plunger was stuck will that have an effect.

wore out · Dec 10, 2021

(quoted from post at 21:06:36 12/09/21)

"good gears inside"

Define "good gears".

Did you mic them and check against correct tolerances?

Did you verify there's only a few thousandths of clearance between the gears and the cover with Plastigauge?

(The reason I ask this is that there have been reports of aftermarket replacement gears being sold made to incorrect dimensions.)

Go down lower on the page and ask about this on the "N"-specific Board, contributor "TOH" is the GURU of these pumps.

Did you replace the bushing and have it bored to size correctly?

Be aware that (as with any gear pump) if the shaft bushing was badly worn the gear will contact the housing around it and mill it away. Then, when a new gear, shaft and bushing is installed the gear will again be centered, leaving excess clearance between the teeth and housing in that worn area, resulting in an internal oil leak resulting in less flow/pressure to the engine.

37 chief · Dec 10, 2021

With a rebuilt pump, your problem is more likely the motor bearings getting a little loose. At ten ponds oil pressure the bearings are getting oil. Good
pressure is always good. The old chevy 6 motors, the rod bearings had no pressure going to them. They just had a dipper on the rod that picked up oil
from the pan. This motor was around for a lot of years With 10 lbs you should be ok. May change to a heaver oil, and pick up more pressure. Stan

Midwest farmer · Dec 10, 2021

(quoted from post at 05:17:03 12/10/21) Full throttle, hot motor? If so I
wouldn't worry too much. Most old N
tractors have low oil pressure.

That was with 5 minutes warm up time and yes almost full throttle.

Gary Mitchell · Dec 10, 2021

Fritz, I seem to recall 50 years ago or so that a guy I worked with, Bill Corbin, took the shown spring, stretched it out, reinstalled it, and there-by increased the pressure by about double. gm

Fritz Maurer · Dec 10, 2021

Gary, I agree that is entirely possible, in ideal conditions. But if the pump is faulty or the bottom end worn out, the oil pressure is already far below what it takes to compress the spring and open the bypass. HOWEVER, if the spring is collapsed or broken, to where it is exerting little or no pressure on the plunger, thereby allowing easy bypass, then yes, stretching the spring will raise the pressure.

Ford 8n low oil pressure

Midwest farmer

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Janicholson

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Midwest farmer

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grandpa Love

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Fritz Maurer

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Steve@Advance

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wore out

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37 chief

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Midwest farmer

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Gary Mitchell

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Fritz Maurer

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