hi guys haven’t been on this in a couple years. Iv got a 99 v10 it was my first truck In high school Iv fought oil pressure issues for years and actually parked it two years ago because of this issue and ready to get it going again. Iv put new crank, new main and rod bearings, new oil pump gears and oil pressure relief spring on it. Iv tried all weights of oil. Iv pulled the pan and checked the pick up tube. But I still loose oil pressure only when it gets hot at idle. With a mechanical gauge it has 24psi cold at idle and will hit 40 or so driving when cold. When it warms up it drops under 5psi and will only get to about 24psi driving. Thoughts? The only thing i didn’t check was the toloranve of the new oil pump gears in the cover my filler gauge would only go to .006 and it called for .003. It is missing one bolt for the oil pump cover can that cause my issue?

 

A missing bolt in the oil pump cover? That REALLY doesn't sound like a good plan.....

Did you check clearances on your rod/main bearings?

 

I can't find a part number anywhere to order new oil pump bolts it's been almost 40k miles with one bolt missing. And I plastigauged all the bearings when I put the new bottom end in it and all was well.

 

could someone explain to me how the oil pressure relief valve operates? I wonder if I could put a stiffer spring in it to boost pressure?

 

Basically oil pressure will push a plunger back against the spring, if it pushes too hard, the plunger will move back past a relief port, and bleed off excess pressure. Not sure changing the spring will help, unless the one that is in there is wrong.... or weak, or whatever.... It mainly deals with MAX pressure. Probably wouldn't hurt to pull it apart, and clean it though, if it sticks open, you will have low pressure.

What weight oil are you currently running?

 

iv tried a couple different weights 10-30 and 15-40 and a quart of Lucas with both weights

 

Then something else is going on. Either excessive clearances someplace else in the motor, or some other avenue for oil to escape, and bleed off pressure. Or, maybe..... a leak in the oil pump pickup? Sucking in some air, so, not getting a full charge of oil?

Trouble is, I suspect the only way you are going to find the problem, is tear the engine down, and inspect everything...... might be easier to just replace it.