Back again I have a 99 D, when I first start it in the morning afternoon whenever, oil pressure is fine as it warms up and you drive it the oil pressure drops to about 25pounds and stays there. Other than they obvious oil pump could the oil pressure valve be messing with the oil pressure, and I was wondering if the low oil pressure would cause the lifters to knock, it does have a lot of miles on it, maybe the engine is just getting tired.

 

In school the instructor said on an old motor, 10 psi at an idle and 25 going down the highway was not uncommon, and acceptable. My two cents is that if it was that low, I would look into it.
I have tried "flushing" three engines over the years and have either clogged the pick up screen or washed the tarnish off the crank to the point of reducing the restriction at the bearings, thereby reducing the pressure in the system. Third times a charm. No mater how much sense it seems to make, I will not do it again.

 

I would replace the oil and filter and ensure you have 10W-30 in it. Because the sending unit is on the top of the motor you could have a blockage at the filter causing the issue. If it still is the same replace the sending unit. It's located next to the distributor cap on the passenger side.

 

just do it ^

 

https://dodgeforum.com/forum/1st-gen...-pressure.html

Mcstealth

 

https://dodgeforum.com/forum/1st-gen...lp-please.html

mcstealth

 

That is a great post as well!