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low oil pressure mystery...

2K views 29 replies 15 participants last post by  grimjeeperyj14 
#1 ·
I had really low oil pressure and recently rebuilt the stock oil pump and put new valve cover and oil pan seals on and I still have low oil pressure. It reads around 5-10 at idle and 30ish at 2000-2500 rpms. I put a mechanical gauge directly off the engine to verify this because the gauge on the dash bounces around everywhere. What else could cause such low pressure. :confused: Note: I also have a really bad lifter taps if that means anything.
 
#2 ·
Are you getting oil in your air filter? What you are probably experiencing is cyllender wear where blowby occurs. This happens from the piston rings wearing to the point crank case pressure escapes the cyllender walls and normally can be detected with oil in the filter.

With oil in the filter or not u need to test your compression on each cyllender to guage where the pressure is escaping the system.. U can rent a compression tester guage at autozone for like 40 bucks and get readings off all your cyllenders and compare to eachother then to the manual specs, if u don't have a haynes manual report back here with the results perhaps or google... I would put my money on internal wear at this point, especially if u got a new pump and mechanical guage spitting out those numbers.
 
#3 ·
Excessive bearing clearance will give you low oil pressure. Why did you rebuild the oil pump instead of installing a new one? A high volume oil pump "may" buy you some time but you do need to fix the bearing clearance issue.
You may be able to install new bearings and dodge a rebuild but then you are left with needing to fix the noisey lifters which will require the head to come off so you can install new lifters and cam.

Dwayne
 
#4 ·
I checked for blow-by already, all cylinders were perfect so I dont think its that. I also checked all the main bearings with plastic guage they were fine too. I couldnt afford a brand new pump at the time so a rebuild kit was easier on the wallet. Any other suggestions of what it may be?
 
#6 ·
When first started the pressure is about 40 and when running for about ten minutes it gets to about 5-10. When running at around 1500-2000 it climbs to about 50. My temp gauge dosent work so I dont know the exact temperature its running at.
 
#8 ·
I would find out for sure what temp you are running at first.....if your engine is running hot, you will have lower oil pressure. Since you have movement on your oil pressure with engine RPM, I would check/change your temp sending unit and wiring first.
 
#9 ·
just a little trick ive learned from a friend. there is a spring inside your pump and if you pull that spring a little bit and stretch it, it will give you a little more pressure. now dont pull the spring straight but just stretch it a little bit and make it just a little longer than it was before and it might raise your psi. if not you may have to go a little more or take a different route.
 
#11 ·
When you did the pump, did you replace ther pressure regulator spring?

Like people said it *could* be bearings, you can do the rod and mains without pulling the engine, though the camshaft bearings can also cause low pressure.
 
#16 ·
I think acceptable oil pres. at idle is around 7lbs so what you have doesnt really sound too bad as long as it runs good. I'd try running some marvel mystery oil in place of a quart of oil at your next oil change and see if that helps out your lifter tap and oil pressure. Ive always had really good luck with the stuff.
 
#17 ·
While I was at lunch this ^^^ is the same thing I was thinking. I also was noting my oil pressure while driving around and mine does exactly what yours is.

At cold start up I have around 40-50 psi
After warm up at idle I have 15-20
Any gas at all i have 40

Factory idle oil pressure is 7psi and a good rule of thumb is that as long as you have 10 psi for every 1000rpm's you are good to go. So I would say your fine I wouldn't worry about it until it reads 0.:thumbsup:

If it bothers you you could run some 10w40.
 
#19 ·
update

Heres a little update of what I have checked so far.
-main bearings are good
-oil pump rebuilt
-valve cover and oil pan seals
-rear main seal replaced
-no blow-by all cylinders read good
-new timing cover seal
-still reads 40ish when started but goes down to 3-5 when warmed up
-reads off mechanical gauge, not the dash gauge
-goes up when stepped on gas to about 30
-lifters tap really bad
-checked cam, all the lobes seem perfect but I cant tell about the bearings

I have gotten alot of good ideas from you guys so far but I still cant diagnose the problem.
Also could it possible to install the oil pump without aligning it to the keyway on the cam?
 
#24 ·
You only need 10 PSI. of oil pressure per 1000 RPM's.

Those mechanical gauges are not too good, since all that tubing is fished around this and that, and most of those cheap gauges, if not all of them are imported. Get the electrical gauges. Will cost more money, but are better than the other ones. They will probably be imported too, but you won't have to worry about that oil tube springing a leak.

I get around 20 PSI in oil pressure when my engine is warm at idle, and I have valve lifter noise at times, and also have a little bit of blow-by in my engine, but she runs great!!!!

Love the low end torque of the 4.2 6-cyl.
 
#25 ·
Remember it is not the oil pressure which supports the bearing surfaces, but the oil itself. Pressure is only the means to get oil into the bearings. If you simply thicken your oil, you are essentially reducing its flow, thus causing the pressure to come up, but are not necessarily doing anything helpful for your engine.
 
#30 ·
Alright so I think Im going to change my oil and filter fiest as it would be the cheapest and easiest solution so far. Currently I have a Fram filter with Quakerstate 10w40 in it. What are some other good filters and oil I should use. I heard Fram is horrible and I should use either Napa Gold, Wix, or K@N filters.
 
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