Ok so I have a 05 chevy tahoe with the 5.3l in it. It has 197k miles and overall runs real good. I bought this truck about a year ago and it had 165k on it at that time and my oil pressure was about 10psi at idle and about 35-40psi on the highway. About 4 months ago it started dropping to 3-5psi at idle and 20-30psi on the highway. Well the 3-5psi was quite concerning. Every time I'd come to a stop at a light or stop sign it'd drop down and the warning bell would start going off. As soon as I started moving again the pressure would go back up and the bell would stop. Needless to say this was very frustrating. I started using heavier oil on my oil changes thinking it would help it and it would keep it from dropping below 5psi for about 2 weeks but would then thin out just enough and the bell would start going off again at every stop. I've watched alot of videos on this issue on the 5.3l and alot of ppl are saying it' the o-rng at the top of the oil pump pick up tube going bad and also alot of ppl say that it's a clogged screen in the tiny filter under the oil pressure sensor. 4 days ago I finally had the time to tear into it and try to fix this problem b4 I do real damage so I changed the o-rng and I put in a new oil pump for good measure and it did NOT change my oil pressure at all. Also I did check my pressure with a mechanical gauge and 3-5psi is accurate. Also there is no tiny screen filter under my oil pressure sensor. According to a ton of videos these 5.3's are supposed to have that filter. So idk if someone removed mine b4 I bought the truck. Regardless I still have bad oil pressure and myself and a few of my friends that are real mechanics are at a loss and are not sure how to fix this problem. Note- there is no engine noise, no knocking, valve chatter, etc. If u didn' look at the gauge at idle or hear the warning bell going off you'd never think anything was wrong. ANY advice would be greatly appreciated. Thanks in advance.

 

I have yet to see an oil pressure sender with a filter, but I dont think that's your problem, regardless, since you have replaced that item. I have never liked the 5.3 liter GM motor since, when they first came out, there were lots of piston slapping issues. I honestly dont know, after what you have posted what the issue is, assuming regular oil/filter changes and no coolant in the oil.

I'd not be using any heavy oil, since modern engines are built to much more strict tolerances, then pre-1990's motors. As you have checked the pressure with a gauge, there must be a leak-down in oil flow somewhere in the engine.

At this point I'd recommend a combustion chamber pressure test to see if you have wear on that portion of the motor. You could also send a sample of the oil to be tested for various contaminants, to see if and what kind of metal or chemical residues are in your engine oil.

 

If you replaced the oil pump, and checked the pressure with another gauge, then there must be something else wrong. Pressure test would be a good start I guess. Question though, did you replace the oil pump with a genuine brand new GM part? Or a re-man part? Reason I ask is I had a car when I was younger, and I had the engine rebuilt by a shade tree mechanic (not a good idea btw) and when I finally got the car back, it wouldn't run right. It actually never ran correctly again, but one of the main issues was the oil pump. The brand new "Re-man" pump he put in would not pick up oil unless primed first (which this car did not do, though I don't know if cars do or not), and when I got a genuine part it worked perfectly.

This isn't to say that this is the cause of low pressure, but maybe it is? As far as the screen goes, I believe they do have a screen though I have never pulled mine out, since its near impossible to get to anyways. On a '05 it may be different, but on mine the screen in down in the tube and you have to use like a dental pick to retrieve it after you remove the oil pressure sending unit.

 

Good Point......Not sure that is the problem but the oil pump in my 05, 5.3 was reman also, I guess it would be worth a try.

 

Not sure that is the problem but the oil pump in my 05, 5.3 was reman also, I guess it would be worth a try.[/QUOTE]
what did you learn, I am having the same issues. I repaced everything you did.
I went to junk yard and found that the 3 of the instrument clusters in the yard were rebuilt. I picked 1. the milage was at 167000 Unfortunately the oil guage read as mine but a bit higher, maybe at 12psi.

 

05 Chevy Silverado. 5.3
Just had the oil pump & seal on the oil tube replaced , WoW I didnt know it could run so quite and good , Mechanic said it was the original GM pump and it was wore out , i had changed everything else on it oil sending unit,, removed screen,, and it was driving me crazy , but now I feel like I have a new truck.. Lol. Hope this helps someone.