I bought a 6.0 2500 farm truck real cheap. Shortly after startup when the fast idle kicks off the trucks oil pressure will drop to zero and the dummy light flashes. As long as I barely bump the gas or keep the idle over 550rpm its over 25/30psi. I figured the farm use clumped up the oil with short trips never fully heating up the entire oil, so I flushed it onced with the engine flush which seemed to help alittle.
It looks like droping the oil pan to clean it out includes dropping the front diff so that last resort.
I've heard some old timers talk about draining half the oil, filling with diseal to flush the sludge out. Are there safe options without hurting seals and bearings or what?

 

If I were you, I would check the actual oil pressure with a good known pressure gauge before you start trying anything else. If that checks out, then I would probably start with the sender which could be partly plugged or just junk.

 

i would swap oil pumps after flushing the motor.

 

The idle sounds like it may be sitting a bit low. If you increase the idle to 550rpms and pressure is fine then I think the oil pressure is fine. But isnt the idle suppost to be around 600-750 rpms.

 

can I adjust the idle manually?

 

O yeah, when I go on a long trip the oil pressure drops to 20 but no lower at idle.

can I reach the sending unit without pulling the intake? I do have a 5.3 sending unit

 

Similar to what mine was doing. I just pulled my engine and found sludge and dried, flaky oil EVERWHERE. There was only about 3 or 4mm in the oil pickup screen where oil could actually get through.

Might try using Trans. fluid to flush it out. Replace 1 quart of oil with 1 quart of trans. fluid.

 

If its sludge it'll probably take pulling the pan off to clear it all out, but might be able to be bandaided if its not too bad. I would also recommend replacing the oil pump and pickup tube o-ring. At least with the pump off and oil pan loose you can use compressed air to blow through the pickup tube and attempt to clean it out.

Do the lifters ever get noisy from lack of oil?

 

i don't think there is anything wrong with your motor, if it is ldling that low and stalls every now and then. there is a software update to fix that. i would do the update before going any further.

 

oh ya your suppose to clean the throttle body also with the update, i would sea foam it

 

my old 400 sbc did the same thing and it had like 500 miles on it or less it's frustrating and i gave up

 

The motor i bought had the same problem, dissassembly found a spun cam bearing. Hopefully yours hasnt done the same thing.

 

if I run it with a spun cam bearing whats the worst that could happen? eat the cam journals up?

 

Most likely I would say its a bad sensor. I would still do a nice seafoaming to clean everything out. Then do the ATF cleaning.