Oil Pressure on John Deere D Needs A Boost

Dennis from Texas · Feb 2, 2014

I have a 1948 styled John Deere D Ser 178788. Assuming my oil gauge reads correctly, my oil pressure never gets to the "M" even at max rpm. At idle it's above the L. I am running a 40w oil and new filter. I understand there is a procedure to increase the oil pressure. Can someone describe the steps. Am I overly concerned about the pressure?

Super Trucker · Feb 2, 2014

Make sure you have the correct gauge for the model . They had different pressure so the gauge is different for the model. If you have the correct gauge then take the top cover off and there is a adjustment bolt to adjust pressure. Its on the oil pump on the top side.

Dennis from Texas · Feb 2, 2014

Thanks for your quick response. I will check the gauge part number first to make sure it is the right one.

gene bender · Feb 2, 2014

Maybe you have a bad guage try anotherone.

WeirdDeere · Feb 2, 2014

If I remember right you're only looking for 10psi at fast idle. I doubt your engine will blow up any time soon. I'd throw a good numbered gauge on it first to see what you actually have. There are good LMH gauges and not so good, so you don't know if yours is accurate.

If your oil pressure is really low, it can be adjusted but it's a bit of a pain, you have to take off the crankcase cover, you can access it then. There's a nut you tighten or loosen to adjust the pressure. It's a bit of a tight fit, but doable, not hard. It's been a few years, but I've done it.

Beware if you do increase the oil pressure, you're likely to get more leaks!

Brandon

Steve@Advance · Feb 2, 2014

I agree with testing it with a known reliable, numbered gauge. As a general rule, 10 lbs. pressure per 1000 RPM is sufficient.

That you have "some" oil pressure at idle is good.

That's where bad oil pressure will first show up, especially if the pressure drops to nothing when warmed up idling. Reason is, the pump is turning slowly and can't completely pressurize the system due to excessive bearing clearance or worn pump.

Providing the pressure relief valve is functioning properly, adjusting it WILL NOT increase idle oil pressure. The relief valve does nothing until the pump speed increases with RPM, thus increasing the volume of oil being pumped, thus overriding the valve spring pressure, allowing excess oil to return to the sump.

rustred · Feb 2, 2014

has nothing to do with leaks.
put a master gauge on it that shows psi and then you will know exactly the oil pressure. the factory gauges usually are in the 3/4's over area. they show no psi.

mj · Feb 5, 2014

(quoted from post at 19:01:17 02/02/14).........
Providing the pressure relief valve is functioning properly, adjusting it WILL NOT increase idle oil pressure. The relief valve does nothing until the pump speed increases with RPM, thus increasing the volume of oil being pumped, thus overriding the valve spring pressure, allowing excess oil to return to the sump.

Stretching the spring back to factory specs for relaxed overall length and/or shimming it works on CASE VACs - across the rpm range - but that's just my experience :?

Oil Pressure on John Deere D Needs A Boost

Dennis from Texas

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