Dash oil pressure gauge reads low

[ExQuisitE]

I have a 2000 Yukon Denali with 160000(almost half is interstate miles) Last week noticed my oil pressure gauge on my dash was up and down and would go to 5 pound if not 0 if idling or stopped. I called a friend and he said it was probably the oil pump. However I drove almost 40 minutes to get home like this and there is absolutely no knocking or different driving habits. Called the guy who rebuilt my trans few years back and he said it was probably the oil sending unit because i would have heard noises or more likely would have blew the engine driving that far if the oil pump was bad or oil pressure was really that low. Recommended changing oil and filter..if didn't work to then change the oil sending unit. So I did a full tune up on it and I changed the oil and filter...absolutely no shavings or murkiness to the oil or gunk/slug in oil. I change oil and filter every 3000 miles and tune up every 3 or 4th time at max when i change the oil. This unfortunately didn't work. Then I had a mechanic check the oil pressure mechanically and they called back saying it was normal at 40psi. They said the oil sending unit was bad and changed it. I then went picked it up, drove about a mile with it at 40psi and then noticed it again dropped where it was before they did anything(calling back tomorrow to ask why i paid to change it). Anyways anyone have a clue what this could be. Just had full tune up/New oil/oil filter/oil sending unit and engine hold normal oil pressure with mechanical gauge. No engine or oil pressure light and no knocking or noise from engine. Never need to add oil from excess burning and nothing other then dash oil pressure gauge seems out the normal. Could this be a oil pump?Bad engine?..(would find that surprising) or strictly a bad cluster and the gauge on dash is faulty? If so can i just go without fixing as it is very costly and just continue to maintain oil changes and checks as normal or any other ideas what could cause this? Would love the feed back as my Denali is deck out with lambo doors, 24 inch rims, aftermarket headers, exhaust, air intake, custom plates etc etc and Ive found these shops see $$$$ signs when I pull in and I would like to have an idea as none of these have worked and I'm completely dumb founded about this.

 

[ExQuisitE]

The truck with mechanical gauge reads 40 psi at 1000 rpms and 40 psi at 2000 rpms/The minimum at 1000 rpms for my 5.7 v8 is 6 psi and 18psi for 2000 rpms. So I'm well over the minimums for psi per rpms. Is it just the cluster? And if so is it really a big deal as long as I maintain the truck as always and check the oil level little more frequently?

 

[ExQuisitE]

So they did the things again free of charge said the sending unit still could have been bad and grounded the wires to the oil pressure gauge on the dash and the arm kicked up when grounded which would lead you to believe the cluster was fine. I have no clue whats going on and shops I've been to giving me the run around or don't believe that I've done these steps already..anyone have any clues here. I'm worried to continue to drive even though everyone keeps saying they would but no one seems to think it makes sense as I don't either and am completely lost. Can these be signs of a blockage in the valve or screen clogged? Can oil pumps start going bad and act like that? Would this be something from the bearings beginning to be worn and letting oil behind them or would you hear noises/knocking or anything out the ordinary other then the oil pressure gauge reading funky?

 

[SteveC]

You have an oil pressure sending unit behind the intake manifold (of course) that is prone to leak and misread the pressure. Do you see any drops of oil coming from the rear of the engine?

It is a plastic sending unit that cracks due to the heat of the engine.

 

[ExQuisitE]

nope already been replaced twice by two different shops...so unless these that common that they even are trash in the after putting in 2 brand new ones then this isn't the problem. Yes the gauge in the truck began reading wrong pretty soon after I started to have a leak.. Its about the size of a dime and only occurs after the oil and truck has been running and stops after the truck is cooled down...I am not sure how the dime size leak is discolored and looks like old oil as the oil in the engine is brand new and clean as a whistle. Either this is a blatant answer and everyone thinks this thread is ignorant or no one know the answer either as i still remain to get a educated response. Hope to hear something soon or I'm just going to drop it off at a certified mechanic and tell them not to call me till the problem is fixed...thus probably get shafted..hope to hear something soon.

 

[alonzo7768]

Ive had this happen .

I have a 99 Yukon Denali. In Jan 2012 I replaced the motor (mistakenly). I noticed that the oil gauge would float and during idle it would drop so low that the check engine light would come on. Since the motor was still under warranty I returned it and they told me that it must be the cluster since my oil pressure wasn't testing low. I took it for a second opinion and got the same response. It's been over a year and I haven't had any oil related problems. The gauge still floats and reads ridiculously low during idle but there haven't been any issues.

 

[ExQuisitE]

Yea this is what im worried about doing since I havent got a straight answer from one shop in this town....I think I'm going to chance it and run it till what ever happends happends...if the engine does go ill replace it...who knows i may get awhile out the engine still and it may be the cluster