ashort

Recently purchased 2008 chevy Silverado with 5.3 engine in it. Has a Jasper reman engine in it out of a junkyard truck with approximately 150,000 miles on it. After driving it about a month and a particularly long ride in it, I stopped and at idle the low oil pressure warning came on. Checked oil immediately, it was full. After it sat for a bit started it and headed home, at first stop sign it came on again, but has not gotten low enough to come on since. Drove and watched oil pressure guage. Had approximately 35 to 37 at 1700 rpm, would drop to about 15 at idle, when warm for both of these numbers. Has good pressure when cool. Replaced sending unit and screen, no change. Put Melling high volume oil pump on with lower pressure spring. Oil pressure is now actually lower at driving speed. About 25 at 1700 rpm. Replaced pickup tube and the o-ring again along with pressure relief valve in pan. Wanted to put higher pressure spring back in pump but couldn't get to it with just the oil pump off. Still same oil pressure I got after changing the pump. Looking at doing Dod delete from here but am not sure. Has already been deactivated in the computer and was before I bought said truck. I'm just not sure that the dod will create the oil pressure symptoms I am having. Just looking for some feedback before I tear too far into this. Does have slight lifter noise but not what I would consider unusual.

tech2

maybe the engine has xsive bearing clearance. run a higher viscosity oil. min pressure is 10psi per 1000prm until you reach the relief pressure.

94burb

There is a guy that has a similar issue as many of us do with hot Idle oil pressure under 20 psi or worse.... His You tube video showed a view from under the block with the pan off and the catch tray mounted under the crank off as well. You can see one of his cam bearings walking out a bit and getting chewed up on its edge. The truck ran with a slight tick but with the bearing out of position, the oil groove between it and the block is now exposed and allowing a free oil flow. This make complete sense for idle issues with low oil pressure. I used the high pressure spring (70psi) when installing my melling hiFlow pump, and sure as it says... I can hit 70 PSI on startups or full open throttle. average driving PSI is around 40-60 depending on rpms, 18-20psi only on hot idle. Its scarry coming to a full idle stop and watching the psi gauge drop as if it weighed 100lbs before stopping at the 20 ish mark.

And again, I have done the physically removal of the AFM Delete (Active Fuel Management): New valley cover, new cam, new lifters, ECM flashed.... Still ending up with the un-explained low oil pressure on hot idle. Its the triggering of the check engine light that pissed me off the most as it deactivates my auto start lol. Most long stops I would give the gas pedal an extra 100 rpm to instantly shoot up the pressure over 20psi while my other foot is on the brakes.

ctryboy310

I had the same problem of low oil psi. I replaced the sensor behind the manifold and problem solved. It was a bitch though

tech2

read his post...he did that.

94burb

Oh and as far as the curious ones on the AFM delete... I DID NOT have hot low oil pressure after the Delete(approx 135k). Happened like 4 years later when I hit about 180k. I did the Delete because of a frozen AFM lifter that seized.