2004 5.3 low oil pressure

[bradshow]

I've down quite a bit of searching to try and find an answer to my issue. I'll start from the begining to see if anyone on here has had the same problem and what the outcome was.

2004, GMC Sierra Xcab Z71 125000 miles.

I was doing some light off roading with my daughter, some decent inclines and fairly sandy terrain. While climbing a hill my "Low Oil Pressure" warning came on and by that time I had reached the top and leveled out and it went away. I had about 4000 miles on that oil change and I was going to change it soon anyways. I use Valvoline max life 5w30. I was heading home on the highway and I came to a small town where I had to stop and while at idle, my oil warning came on again and I saw that the pressure gauge was at zero. I stopped the truck and checked the oil, still full. While driving the oil pressure was around 20-25 acccording to the gauge. I could hear no signs of anything going on while the engine was running at idle so I drove back home.

The initial fix I found was to replace the oil pressure sending unit, I did and there was no change to the gauge reading. I changed the oil and didn't find any traces of metal in the old oil. Still, low pressure at idle, 20-25 while driving.

I finally just unplugged the sending unit so the alarm wouldn't go off everytime I stopped.

This brings me to the other 3 items I came across. The servo on the gauge cluster is bad, the oil pump is bad and I spun a cam bearing.

The truck doesn't run any different and it doesn't make any noises to say it was not getting proper oiling as far as I can tell.

I haven't had a change to hook up a mechanical gauge to the truck to see what it is doing and won't be able to until I get back from deployment. If that comes back as low, how will I know if it is a bad pump or a bad cam bearing?

I initially wanted to just buy a new engine or do a swap but if I don't have to do that for a while longer I would like to just fix this one for now.

Anyone who's faced a similar ordeal, please chime in.

[ecld_07]

Does yours have an oil cooler system? Could it have crushed one of the lines running to/from cooler

[RedHeartbeat]

Put a new melling pump in it. Factory pumps are notorious for the oil pressure relief piston sticking in the open position.

[bradshow]

Put a new melling pump in it. Factory pumps are notorious for the oil pressure relief piston sticking in the open position.

I've given some thought on swapping the oil pump. From what I can find its not too hard of a job, just have to raise the engine up a tad to get the oil pan off. Where would be the best place to find a "how to" on swapping the pump other than buying a service manual? Anything on the cheap will help.

[sprayedenali]

The hardest part is actually getting to the pump. Once you get the pan and timing comer off its 5 bolts and the pump comes right off. Clean out the pan real good when you have it ohh and make sure the pickup tube is clean as well. Replace the I-ring for the pickup tube with the new pump and I'd bet you'll be good to go!

[bradshow]

Man I hate shotgun troubleshooting. Is there any way to tell if its a bad pump or a spun cam bearing without tearing anything apart? Probably a dumb question but I'd hate to waste the time and energy to swap the pump and it still run low pressure. I guess its either spend the $150 bucks and swap the pump, pray its the problem or pay the $3300 for a new 5.3 and know its fixed. 125k isn't that much in todays mileage and I know at least half of that way pure highway miles so its not like this trucks been ragged on too bad. My gut wants to tell me its the cam bearing just because I know the truck was under a good load while I was off roading when the issue started but wouldn't I hear some strange noises coming from the truck? I know it builds pressure while I'm driving but only up to 20-25 according to the gauge and at idle its zero. This is stressing me out, even more because I can't do anything until July when I get back to the states.

[RedHeartbeat]

Gen3 engines have priority oiling systems, the crank and rods get oil before the cam so if you have low oil pressure its likely the lower end bearings rather than the cam bearing.

[crisdg@khp]

X2^^

[RADO_4U2NV]

If it had a bearing problem you will see metal shavings in the oil when you drain it. It is a cheap part but most low oil pressure issues I have seen has been the o-ring for the pick up tube where it goes into the pump. The pick up tube only has one bolt holding it in instead of one on each side. Sorry design in my opinion.

[bradshow]

I've decided to intall a new oil pump and see what happens. I'll be sure to check the O ring on the pickup tube. Is it possible to remove the whole oil pan while the engine is still in the truck? If so I want to replace the pickup tube as well.