2001 Burban, almost no oil pressure even after replacing the oil pump

[ScottyBoy]

So some of you may already know my situation as I've mentioned it in another thread,but I figured I'd make a dedicated thread for my issue.
This all started about 2 weeks ago, I got a "Low Oil Pressure " warning light on my dash, and my oil gauge dropped to just below about 10psi. I replaced the oil sending unit, NO CHANGE. So then I bought a manual pressure gauge, and after hooking that to my engine I saw that it was reading the same as the stock guage on my dash. So I ordered a new oil pump and pickup tube/screen. And if course all the needed gaskets and seals involved when you remove the water pump, timing cover, and oil pan. So I pull the oil pan and it's FULL of thick sludge. The screen was also mostly clogged with sludge and debris.
After much scrubbing and cleaning, I finally got the oil pan completely clean. Then I removed the front timing cover, and thankfully saw that the rest of the engine although not exactly CLEAN, had nowhere near the amount of sludge that the oil pan had.

So after much cleaning, (and aggravating my back) I FINALLY get the new oil pump installed, the new pickup tube and O-ring, then re-install the timing cover, oil pan, water pump, crank pulley, and everything else that I removed in the process. Get it all filled with fresh oil and fresh coolant, then I pulled the plug behind the power steering pump and wedged a hose into that hole to prime the oil pump as many videos across the internet have instructed to do to on LS engines. After all that, I finally go to start it up and I have a VERY loud lifter tap, and very low oil pressure. I figured maybe it just had some air in it so I I let it run for a minute to try and warm up and hopefully bleed any air out. At this point the oil pressure was about maybe 15psi. I revved it and got it up to almost 30-35psi. After a few minutes of letting warmup and trying to bleed any air out of the oil and the coolant, the lifter tap finally quieted down a good bit. I've always had a lifter tap ever since I bought this rig, but it's usually pretty quiet, and almost completely goes silent after the engine warms up. This was the loudest it EVER been. Was so loud it almost sounded like a rod knocking. Anyways, after warming up the engine for a few minutes, the oil pressure got even lower. It was no higher than about 5psi at idle unless I increased the engine RPMs.
I installed a Melling "high volume" oil pump so I figured I should have even MORE pressure than normal. Something is obviously wrong here, and I have no idea what to do at this point. The ONLY thing I can think of is to drop the oil pan yet again and double check the O-ring on the pickup tube. Also thinking I should do a compression test to double check that I don't have something wrong with my engine.
Does anyone have ANY suggestions or insight for me at this point? I've thrown so much money at this thing the past two weeks between buying all these parts, all new fluids, and several new tools I had to buy just to complete this job. I'm just VERY frustrated with it at this point.

 

[Mudsport96]

Id double check the oring.

 

[OR VietVet]

With all that sludge and over time, the low oil pressure, I would be worried about crankshaft and camshaft bearing clearance. Sorry to say that the damage may already be done but yes, double check that o-ring. With the sludge from before you may have drain back problems at the heads as well.

 

[blueinkd]

So when I did my rear main seal I made certain to replace the oil pressure barbell. Cheap piece and is a big part of the oil system. I wonder if maybe the oring on yours has failed. Just a suggestion. See video below.

 

[drdave81]

You may also look into the pick up tube girdle. It keeps the pick up tube from moving in the oil pump by bolting down the other side of the tube. If it's not that though, I think you're looking at major work here. My first thought after reading was also bearing have gone bad. That much sludge is a big indicator of maintenance neglect.

 

[ScottyBoy]

You may also look into the pick up tube girdle. It keeps the pick up tube from moving in the oil pump by bolting down the other side of the tube. If it's not that though, I think you're looking at major work here. My first thought after reading was also bearing have gone bad. That much sludge is a big indicator of maintenance neglect.

I agree, I should have been changing my oil more often. I don't put a lot of miles on my truck and I was changing the oil based on MILEAGE and not paying attention to the age of the oil. Apparently low mile OLD oil can be just as bad a high mile oil.

 

[OR VietVet]

I agree, I should have been changing my oil more often. I don't put a lot of miles on my truck and I was changing the oil based on MILEAGE and not paying attention to the age of the oil. Apparently low mile OLD oil can be just as bad a high mile oil.

Yes it can. Did you use petroleum based oil or synthetic? What brand and quality of filter. Cooling system problems, too hot, can break down oils as well. Leaking oil and then throwing in what you have around can cause problems if not the same oil as what is in the engine.

 

[ScottyBoy]

ALWAYS use Synthetic oil, and I usually either use Amsoil XL Series or Mobil1. For filters, I either use a Mobil 1 filter, or a Wix XL series filter, depending on what's easier to find at the time. Sometimes people are out of the Wix, sometimes they are out of the Mobil1 filters. I usually order a case of Amsoil, but the times I forget to order, I just buy some Mobil 1 oil locally. I have been running my oil for about 5500 miles, but that can sometimes mean I go nearly a year on that oil. I now realize that's a VERY bad practice. I need to change it every 6 months even if I only put 2500 miles on it.

 

[Fless]

I tend to disagree with some of these assumptions, based on my DD's latest oil report from Blackstone:

 

[OR VietVet]

Yes, max time for me is 6 months, even with synthetic. Good choices, IMO, on the oil and the filters. If you are only putting a low amount of miles on the engine in a year's time, that means the water condensation that builds inside the engine as it warms up and then if shut off soon after, that water drips in to the oil and contaminates over time. Is especially brutal on petroleum based oils. As I said above, other factors can contribute to the oil break down over time. Plus, problems with the engine that are great one minute can be bad the next, like fuel contamination that exceeds the normal small/minute blow by.