Oil Pressure Issues

[89fox5_0]

Just would like to say whats up to everyone. i am new here and trying to figure it all out. give me sometime and im sure i will get it. Anyways Brand new rebuilt 302 ho. it only has 3-4 miles on now. I was driving it around the block a few times on its madien voyage. Relized that my oil pressure was low. Took it back to the garage and put a mechanical gauge on it. I was at about 10-15psi at idle. 21 -24 at about 2500rpm. i let it sit overnight and started it the next day. my pressure was 45-52psi. at idle. after it warmed up you could watch the gauge slowly drop off to 10-15psi. then crack the throttle body open and it would only get to about 18-22psi. thats it. Oh yea Brand new oil pump with engine. Any ideas. Thanks in advane

 

[BK_CAULEY]

and these reading are from an aftermarket gauge? did you reuse the stock pickup tube and screen by any chance?

 

[89fox5_0]

Yes i sure did. But made sure it was solvent cleaned and dried before i put it back on.

 

[BK_CAULEY]

when the motor was rebuilt was it hot tanked and cleaned? or was just the rotating assembly freshened up.

 

[89fox5_0]

Hot tanked the whole works. everything is new when they rebuilt it. I think i may have some junk in the oil pressure relief valve. And it is holding the spring open futher than it should be. Not letting it build any pressure when the oil is hot and thinned out. When the engine is cold and oil thick it has great pressure. but when its warmed up and the oil is thinner pressure sucks. What ya think???????????

 

[90lxcoupe]

what are the bearing clearances?

 

[Mustang5L5]

What grade oil are you running?

Those numbers are pretty low. Typically whay i see on my 106K mile original 5.0 is 20psi at idle and 55psi at anything over 1500RPM.

 

[oh9mustang]

Oil gets thicker as it warms up.
A 5W20 oil is the thinnest when cold and thickest when hot.
If the oil is at its thickest and the pressure drops, there is (1) a obstruction,
(2) a cracked oil pump, (3) a oil pump gasket problem.

 

[89fox5_0]

Well i can tell ya lastnight i got the oil pump and pick up tube out with out pulling the motor but i will never do that again. I made the decision this morning i am going to pull the motor and plastigauge all the bearings. after looking at the pump and pick up tube there is alot of metal dust in the screen and in the bottom of the pan. And that worries me. I am using castrol 10w40. that is what they reccomend i use. Thought that was different but hey they rebuilt the thing. My other motor i used straight 30 for the seating of the rings for about 300 miles. then went to 10w30. Its starting to really get on my nerves and its about to the point where i put a for sale sign in it.

 

[oh9mustang]

Oil weight depends on Bearing clearance, putting a 30W oil through a 1000th clearance bearing space is asking for trouble. If they told you 10W40 they must be working with 1 1/2-2 thousands clearance. Or maybe they are just guessing and didn't measure the crank and 10W40 is what they always use.
Unless it's knocking the metal dust. probably come from cam bearings or the oil pump gears. New bearings will also put metal dust in the oil. Putting new bearings in, you should run it for a few hours and then change the oil.

 

[spoulson]

89fox5_0, did you ever find out what was wrong? I'm having pretty much the same exact symptoms on a recently rebuilt engine.