Join Date: Nov 2005
Location: Diego Garcia, BIOT
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
5.9 V8 - Low Oil Pressure? What's yours?
The '98 Ram we recently purchased (5.9 V8; auto; 2500 4x4), seems to have low oil pressure, according to the gauge. With the engine off, the needle's pegged down below zero, which is normal. With the key in "On" position, it moves up to the zero, like it should. I fire it up, and at a cold start-up, pressure reads about 50 psi. Then, as the engine temp slowly rises to operating temp, the oil pressure slowly lowers to about 22psi. I'm glad it's not a quick drop, but still concerned that it drops at all. I'm not yet familiar with the Rams, but I thought that the pressure would increase with rpms. At least with every other vehicle that I've ever owned. But this truck, the pressure sits in one spot, and doesn't fluctuate at all. Stays steady. If I stop somewhere, and go to drive again, if the engine is still warm, the pressure reads 22psi. Only after sitting a few hours will is start out up around 50 again. And then the drop starts all over again.
I did my usual background check, as I do with all my vehicles, and checked the dealer service department visits, so that I know what work has been done in the past. Interesting enough, I found out that around '99, it was in for low oil pressure, and they finally replaced the heads to cure the oil flow problem. Our fear is that it may be acting up again, and that we may be screwed $ wise. No more warranty left. It only has 52K miles, which is why we bought it. On the DodgeForum site, I had one interesting reply:
"There is no possible way for the heads to be at fault. I consulted my repair manual for this problem and the oil pressure should read 6psi at idle and 30-80psi @3000rpm. Personally, my engine runs between 35-45psi all of the time, even at high rpms. Another possibility is the oil line plug located in the vertical passage at the rear of the block between the oil to filter and oil from filter passages. It is mechanically seated and if improper mounting depth is present a dowel drift can be used to reseat it to correct dimensions. Accordingly, this can cause low, high, or erratic oil pressure signals to the sending unit. Unfortunately, a certified mechanic is probably the best solution to have this checked. I could see this being bad and the tech's that changed the heads out missing it or believing the heads weren't allowing proper oil flow, instead of it being improper flow to the heads. I really hope you understand all of this, tended to ramble a bit. Any questions, hope I can be of further help."
Just wondering what others have for running oil pressure, so we know if we have to look at it closer. I swapped out the oil sender, and it still acts the same. It has 40+ psi at startup, and then drops down to about 20-25psi after the first mile or so of driving and just sits there for the rest of the drive. My next thought, is to install a mechanical gauge to eliminate the dash one.