Hey all,

picked up a 1996 B2500 conversion van 5.2 for $200. Been sitting for quite some time. 119,000 miles. Replaced all the fluids I can in it.
Fresh brakes all around.
Engine and trans are in phenomenal shape for its age
EXCEPT
Been getting low oil pressure after engine warms up.
Swapped oil pressure switch with no effect. oil and filter replaced.
Would a new screen help? Or should I go the whole nine yards with the pump as well?

 

When oil pressure falls after a warm-up it usually means a bad main or rod bearing.

 

is this something to worry about? my van, after driving for over 30 minutes, the oil light will come on and teh needle will drop all th way to the bottom. there is oil in it, and everything seems to run fine.

 

Yes it is, eventually the engine will seize if this issue isn't corrected.

 

The minimum oil pressure at idle for a 5.2 from the 90's is 6 psi. Once the pressure drops below 6 psi, the light illuminates in the dash. Yes low pressure on a hot engine at idle can indicate worn bearings. But all is not lost, the engine could very well run tens of thousands of miles, or more, in this condition. Test the actual pressure with a gauge. There is a world of difference between 5 psi and 1 psi. By the way, there is a huge window on the top end of the oil pressure. At 3,000 rpm expect to see between 30 and 80 psi.

Bump up the weight (viscosity) of the oil used in the engine. This will give you additional pressure at idle rpms. So, if you are using 10w 40, go to a 15w 40, or if necessary, 20w 50. Or you can even half step the viscosity -- 2.5 quarts of 10w 40 and 2.5 quarts of 15w 40.

 

First be sure that it's not just the guage or the port by the guage being clogged... Might be worthwhile to remove the sending unit, make sure there's not a bunch of crap in the port, maybe even turn it over to be sure you get a good stream of oil out, then put a mechanical guage on it to check it... if it still reads the same, look elsewhere.

if it sat for a long time, could be a bunch of crap in the pan, screen, filter, etc. how dirty did the oil get how fast? migt also be worthwhile to change the oil and filter several times (ie especially if you're getting a bunch of black stuff out... filters can clog up and block enough flow to make idle pressure look pretty low if there's a heavy amount of particulate being filtered out.

I like rotella 15-40 (non-synthetic) for my 5.9 and 5.2. It's cheap and has a good detergent package in it. That said, castrol

Lastly, don't despair right away. My memory sucks sometimes, but I swear, maybe 8 or so years ago, my 95 ram truck 5.9 was doing something similar, but I don't remember for certain what "fixed" it. I think it was dirty / plugged port / faulty sensor or guage kind of problem... I know that it's got another 100k miles on it since then... at 260k now on the original engine and it holds 40psi oil pressure at pretty much any rpm still...

 

Update:

Pan had plenty of gunk sitting at the bottom. Deep cleaned the pan, replaced the oil pump and screen, and replaced the pan gasket. added a bottle of slick-50 as well. Pressure returns!! after a little while, the gauge drops, but i do not hear any tapping, so i think the sending unit (which i replaced a month ago) just isn't getting a clear signal. After i put a few more miles on her, ill change the oil again and see how quickly it gets dirty. Praying i don't have to do the bearings. I'll replace the valve cover gaskets in the near future (not the worst, but due for replacement).

 

What are your pressures at (1) startup and (2) at fully warmed up at idle and (3) at 2000 RPM's. You need to specify pressures otherwise your comment is useless.
8)

 

Very valid point. Haven't had time to hook up a gauge due to work schedule. Once I do, I'll update with numbers.