zanebenziger27

I have a 1999 Silverado with the pre AFM 5.3. 285,000 miles on the truck. It’s been taken care of and the oil has been changed regularly by me and the previous owner. I have replaced the oil pressure sending unit about 25,000ish miles ago and it fixed the old oil pressure issue.

While I was driving; I noticed my oil pressure was a bit low at speed, somewhere around 25. I didn’t hear any ticking so I kept driving. I looked down at the gauge and it was reading 20 on the way home and starting to tick. So I pull in and it’s at 10 pounds and ticking.

I check the oil and it’s topped off, I look for any oil leaks and there are none. I can’t rightly see it being engine wear either, considering it happened rather suddenly.

When I went out to check on the truck the next morning, I started it, and it read 0 pounds. All the lifters were ticking. So I shut it off; checked the oil, and started it again. It ticked for a bit, then the oil pressure rose to 20 and the ticking stopped. At temperature when the truck is idling, the oil pressure sits around 20, but barely goes up with higher RPMs.

FFDP

iTrader: (2)

Either the oil pump is failing or the pick-up tube o-ring is shot.

Those are my two guesses. I'd start with looking at the o-ring first.

RDF1

Oil pickup tube o ring would be the first thing I would check/replace.
while your there you can shim the oil pump pressure relief spring with 3 or 4 #6 washers.
All the older engines I've rebuilt had cam bearings worn out. Some just new cam bearings had them back going with good pressure.