weird oil pressures...
Thread Starter
|
Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
weird oil pressures...
Hey all...I's gots a scenerio fer ya's. Why is when I let off the gas or go down hill my oil pressure rises anywhere from 5-30psi??? When I change gears the oil pressure will go up about 3-5psi then come back down. Here lately I've noticed it's been a little low for some reason. The oil pan is full and the oil pump is only a tat over a year old. Is this bad or normal? It kind of has me concerned.
Freshman User
Joined: Jan 2003
Posts: 36
Likes: 0
From: ny
weird oil pressures...
well this is whats happenning when youre engine is under load you are using power from the engine wich turns the oil pump thus when you let off the gas or shift you are reliveing the load on the engine this is not bad but you can fix it buy buying a high volume oil pump and a pressure relife spring this will jump the pressure up to 80 or 100 lbs but be careful cuz oil press over 100 lbs will wash out the berings i had the same problem with a 400 you can get the spring from mellings or jegs www.jegs.com
Lead Driver
Joined: Dec 2002
Posts: 5,491
Likes: 16
From: Kuna ID
weird oil pressures...
What does it mean to wash out the bearings? I just hooked up a mechanical gauge in my truck, and I think the PO may have put in a high pressure pump, cuz my gauge read 80psi while driving and 40psi while idling.
Posting Guru
Joined: Dec 2002
Posts: 2,003
Likes: 2
From: chicago burbs
weird oil pressures...
1ole4d, sounds like you are describing a low oil situation but you say it's full. is it possible the pick-up screen is so close to the bottom of the pan that it is restricting the ability to get oil to pump? it's a common problem with barrel pumps, they have to sit up off the bottom to get oil. is it possible the oil pan took a hit and closed the gap? as far as washing out the bearings goes, i always thought that was an excessive pressure condition that oil flow actually removed bearing material or flowed behind the bearing and caused damage,like on bearings that the oil flows through a hole in the bearing to get to the journal(cam bearings, main bearings)
Trending Topics
Thread Starter
|
Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
weird oil pressures...
yeah...I checked the oil pan. No dents or anything. The motor has held excellent oil pressure since I put in a new pump a little over a year ago. I think all the revs have finally done the bearings in though. I never did change them when I did the oil pump. Now it gets about 10psi at idle and only 20-25 running 55-65 at 2000-2500 rpm 
. You guys think if I went with a high volume oil pump and new bearings that it will take care of everything???
. You guys think if I went with a high volume oil pump and new bearings that it will take care of everything???
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Senior User
Joined: Jan 2000
Posts: 354
Likes: 0
From: Irving Texas
weird oil pressures...
I have a 87 f-150 302.
With a high volumne oil pump.
Once the truck warms up.
When i am driving at 1500 rpm in over drive (guess 60 mpg), I will let off the gas and my oil pressure goes from 40 to 65 psi.
When i give it gas it goes back down to 40.
When i stop the pressure goes down to 20 psi.
So what causes this ???
With a high volumne oil pump.
Once the truck warms up.
When i am driving at 1500 rpm in over drive (guess 60 mpg), I will let off the gas and my oil pressure goes from 40 to 65 psi.
When i give it gas it goes back down to 40.
When i stop the pressure goes down to 20 psi.
So what causes this ???
Junior User
Joined: Nov 2000
Posts: 52
Likes: 0
weird oil pressures...
A friends truck had a plugged pick-up screen, a bunch of crud under the tin plate where you couldn't see it. A new pump and bearings didnt help. The thicker the oil the worse the pressure. I guess the pump was good but couldnt suck up enough oil. This caused very weird pressure readings. Remember the rule 10 psi for each 1000 rpm, keep this and no problems.
New User
Joined: Mar 2003
Posts: 4
Likes: 0
weird oil pressures...
It sounds to me like when you're running 1500 your engine is letting more oil run past the bearings and bores, and when you let off the gas the consumption slows before the residual pressure in the system dissipates. It could be more specific than that though, when you coast, the crank could be rolling up and blocking the cam feeders on the mains. This is really just a tighter seal, they are relieved so they can't get blocked really.
When you idle, the oil pump is turning much slower, and puts out a little less on the ratio to consumption. This is fine, because at idle, there is virtually no load on the bearings anyway. As long as the pressure rises with rpm, the pump is keeping up with consumption. This does not include the coasting when it spikes. I'm talking about steady cruise, it should be higher at 40 than 30, higher at 70 than 60, and so on. If those were the pressures on my engine that you reported, I would have no problem with them at all.
When you idle, the oil pump is turning much slower, and puts out a little less on the ratio to consumption. This is fine, because at idle, there is virtually no load on the bearings anyway. As long as the pressure rises with rpm, the pump is keeping up with consumption. This does not include the coasting when it spikes. I'm talking about steady cruise, it should be higher at 40 than 30, higher at 70 than 60, and so on. If those were the pressures on my engine that you reported, I would have no problem with them at all.
Last edited by jginva; Mar 27, 2003 at 03:07 AM.
