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Replacing oil pump without pulling engine

sd_iconoclast

Active Member
Joined
February 17, 2012
Messages
91
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City, State
San Diego, CA
Year, Model & Trim Level
1991 Explorer
I have a '91 EB 4x4 with about 175K mile and I just fixed a bunch of problems by replacing a head that had a burnt exhaust valve. So now the car runs pretty well except that I still have an issue with low oil pressure. After I have been driving it a while, the engine will idle at roughly 700 RPM and I will see the stock gauge (which I know is really an idiot light) flop back and forth. My aftermarket oil pressure gauge seems to confirm this by showing somewhere around 7 or 8 psi.
I have replaced the fuel pump and regulator recently and this seemed to help the idle speed. Before that, the factory gauge showed 0 all the time.
So I am thinking about trying to fix this by installing a high volume oil pump, but it looks like a big job.
Has anyone ever replaced the oil pump without pulling the engine? Maybe by unbolting the front axles?
Or is that just as big a job as pulling the engine?
 



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What weight oil are you running?
How is it with straight 30 or 40 weight?
Old trick to "help" on old tired engine.
I have run all the way to 60 in Cali.
DO NOT WING IT (rev or high RPM)
till oil is warm.
 






I am NOW running 10-40 with Rislone and Lucas Oil Stabilizer.
I had considered 2-50, but I have not tried straight 30 or 40 weight.
I am not sure if I am doing any damage. I have worked on Buick V-8s that idled at 2 or 3 PSI for quite a while.
I am not sure I have the option to not "WING IT" as I live a the bottom of a long steep driveway.
 






When oil is cold it is thick as molasses. Revving the motor can over-pressure
and rupture an oil filter. Oil pressure bypass may not be able to vent excessive oil flow.
Living in SD it's not that cold so, warm-up is a couple of minutes. Now if you go up
to Julian in the winter etc. You get the point?
Try 30 weight first.
 






Maybe this is another clue:
Even though the car seems to run pretty well, and I only have the low oil pressure when the engine is warm, at all times, i start to get what sound like "valve clatter" right at 3000 RPM even though I have plenty of oil pressure, cold or hot.
But, I dont think it is valve clatter as I recently replaced all the lifters. I have taken to using rislone to decrease the noise, and it works pretty well.
without rislone, the car will clatter for about 30 seconds at startup, particularity if I havent driven it in a while
 






To remove the oil pan, you need to lift the engine several inches to clear the cross member. Pulling the axles won't do it because the cross member will still be there. I have a solid front axle so I modified the cross member to make it bolt in under the pan.

My engine idles at around 800 in gear, has about same mileage on it and has no clatter.
 






I can tell you this the way these oil pumps are designed if it is spinning it is making oil pressure
MOST low oil pressure issues in these engines are due to the buildup of carbon, blocking oil passages, including the drain back passages
You can combat the sludge without changing the oil pump
Meaning ATF, diesel oil, marvel mystery oil, or just mobil one full synthetic oil can all help break up the carbon deposits and get your oil passages flowing again
Replacing the oil pump in the truck will likely result in the same low oil pressure condition
Consider pulling the engine and giving it a complete clean and re seal
Or run it with detergents in the oil and watch the oil pressure come back
 






1 ounce of seafoam per quart of oil does a good job of cleaning things out, as well. (4 to 5 ounces for your engine) I did this to mine, and it even got rid of the cold start valve tick that I had. BTW, I've got around 470,000 miles on the original engine.
 






Great suggestions guys. I will try the cleaning suggestions today. My engine might be particularly susceptible to the sludge buildup at I have twice ran for long periods with coolant getting into the oil due to cracked heads.
I will report back
 






I’ve been on this forum for over twenty years and I can’t recall seeing any threads where someone is replacing an oil pump. Maybe there have been some, but it doesn’t seem to be a common failure at all, IMO.
My 93 has over 350,000 miles with no engine work ever.
 






correct
If you have held the oil pump from the pushrod engines in your hand you can see there is like no failure point to where they can make low oil pressure
If they spin they are producing oil pressure
The only thing that can cause low oil pressure (compared to none) is cavitation (Ie a hole in the pickup tube or gasket where the pickup tube meets the oil pump) or flow issues (clogged passages and pickup tube)

Taking the engine down to the lower intake manifold, take the valve covers off and have a look see
No way in heck would I attempt to do an oil pump IN THE TRUCK unless I did not have the stock engine cradle (ie a solid axle or custom frame)
Otherwise it takes 4-6 hours to completely pull the 4.0 and do it right

I like diesel oil for cleaning up sludge
people swear by marvel mystery oil and seafoam, any of the products that break down carbon deposits is what you are after
For me I would run straight diesel oil for a few hundred or a thousand miles with a manual oil pressure gauge in place and watch the engine get its oil pressure back
Slowly return to a mix of conventional oil and diesel oil until the oil pressure is back to spec and then switch to mobil one full synthetic to finish the job. Change the filter very often during this process
I know of pushrod 4.0 and 5.0 that had 0 oil pressure at idle that are still on the road today doing this procedure
 






When I had to replace a leaking pan gasket, I thought about replacing the oil pump. After doing a search and finding no failures I cleaned up the OEM pump and put it back in.
 






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