Dropping Oil Pressure

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My oil pressure is 25# at idle, and 60# during cruise at 2000 rpm (70 mph). When I increase throttle from this cruise condition, the oil pressure drops to 50# and stays there until I backoff the throttle. If the transmission (Allison 6 speed) down shifts during the acceleration (rpm now 2400+) the oil pressure goes back to 60#. The drop in pressure occurs about 1 second after throttle increase

This only happens when the engine has been at full operating temperature for some time. I may have had this problem for a while, but only recently noticed it.
Is this oil pressure fluctuation something to worry about?

My Cummins (230hp) is in a 22,500# 1995 Safari pusher motorhome with 30,000 miles on it.

Thanks.

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Tom Bora: 1995 12V/230 Motorhome

 

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Sounds to me that the oil pressure sending unit is having a moment! Mine did about the same, so I changed it and stopped the problem. .

Rick

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RICK
97 2500,CC,5 SPEED, 3. 54 Limited Slip,Psychotty System,K&N, Pre-Turbo ISSPRO 3" Pyrometer & Boost Guage,Silencer Ring Removed
12,000 RBW 5th Wheel Hitch,25' Excel 5th Wheel,Rancho RSX17000 Shocks,Amsoil Dealer,Straight Piped

 

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boratf,
25 psi at idle is Ok. 50 to 60 psi at the rpm and speed your running is good.
But why it would drop when you give it the gas or come back up when passing gear kicks in? I would as Rick suggested check out oil pressure sending unit.

 

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it is common for snders to get bad spots in the resistors ,giving this exact situation. If it worrys you ,hook up a manual guage and see what happens under the same situation.

 

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According to my 96 Shop manual, when oil psi exceeds 65 psi (which might happen upon sudden increase is rpm, oil pump is a gerotor pump so displacement is proportional to rpm) a 'oil pressure regulator valve' will open to allow part of the oil to drain back into the pan. This valve is located internally in the oil filter block assembly I believe. Manual states that a 10 psi difference from one engine to another is within the manufacturing tolerances.

You could also be momentarily bypassing your oil filter if it is clogged when it sees the higher flow rate. This bypass is located in the oil cooler cover. The manual states that it will open when a differential pressure drop of 20 psi through the oil filter. They further state that a plugged oil filter will typically cause a 10 psi drop from 'normal' operating oil pressure.



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Redram:

I had also thought about the pressure regulator and oil bypass..... but the drop in pressure occurs before any rpm increase is noted. Also when the trans down shifts (higher rpm) the pressure stays up OK.

Like some others mentioned, I am going to check out the pressure sending unit. What do they cost to replace?

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Tom Bora: 1995 12V/230 Motorhome

 

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If I remember correctly mine cost about $10 from www.moparsforless.com

Rick

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RICK
97 2500,CC,5 SPEED, 3. 54 Limited Slip,Psychotty System,K&N, Pre-Turbo ISSPRO 3" Pyrometer & Boost Guage,Silencer Ring Removed
12,000 RBW 5th Wheel Hitch,25' Excel 5th Wheel,Rancho RSX17000 Shocks,Amsoil Dealer,Straight Piped

 

[Archive]

Rick,

URL didn't work. Try this one: http://www.mopar4less.com/



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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,BD valve body,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver