I have a 2003 chevy 1500 with a 5.3 and I'm having an issue with the oil pressure, when I start the truck in the morning and let it idle my oil pressure will be at 35 and then start to drop down to 10 and back up to 35 and back down again when I rev the truck it goes up to 40 but no matter how high I rev it it wont go over 40. When i hit the road it will stay at 35 to 40 but when i stop it will drop to 10 and back up again. Once the truck warms all the way up and I run it for about 10 mins it will start acting normal and the oil pressure wont drop below 35 and will go to 60-65. When I kill the truck and let it cool down and get back in it an hour later it starts over again, I've already replaced the oil pressure censor and new oil change and it still does it.
any ideas?

 

I just started having a similar issue with my 2005 5.3 Suburban. I noticed a ticking last week at a red light while driving to work (~20 minutes of driving). It wasn't there when I started in the morning and went away by the time I got to work ~10 minutes later. The tick went along with engine speed but I had oil pressure between 40-45psi while I was driving normally between idle and 2000rpm. Anyways, I put half a can of seafoam into the oil and drove it for a week ~100 miles and changed the oil with my usual Rotella T6 5w40 and a new Delco filter.

Now that I've been paying more attention to the oil pressure I've noticed now when I first start up in the morning, my oil pressure stays at 35psi and seems to try hard to get up to 40psi but won't make it there even at 2000rpm. After driving for 15 minutes or so and letting some heat into the oil the oil gauge starts to act seemingly normal. At idle the pressure is right below 40psi. At 1000rpm, the oil is at 40psi exactly according to the gauge. 1500rpm gets ~45psi and above 2000rpm it's between 50 and 55psi.

The most confusing thing about this is why it acts reverse of every other car I've driven where the pressure is high when cold and lowers when warm. WTH is going on with this thing?

 

Manual calls for 5w-30 so that might be an issue. Maybe not. The parts the automakers are using are oftentimes not made in the USA, so Q-C is out the window these days. Also Delco oil filters are OK, but Wix is better, IMO. Me, I am sticking with my old Chevy 1998 K-1500 until I drop dead. Back then, Q-C was MUCH better, IMO.

 

I would have assumed the cold weight would have acted similar being a 5W but I'm no engineer.

I was thinking about something over lunch and was wondering what everybody here thinks. If the O-ring on the pick up tube is going bad could this be possible. While it's cold, the oil is thicker and maybe there is air getting past the o-ring just enough to cause a "low" pressure issue and when it warms up the clearance goes away due to thermal expansion and closes up the gap. No air being sucked in allows the proper pressure to build up and no more issues. Maybe that could have explained the ticking noise from earlier. Possibly a lifter got full of air?

What are your thoughts?

 

The newer 5.3 motors don't use a traditional oil pump like my 1998 K1500 does, and since I am only a rig driver, I haven't dealt with the new oil pumps at all. That said, sure it could be a bad O-ring, but I have seen lots of issues with the newer 5.3 liter motors, not to touch one at all. First it was piston slap, and now it seems the new
oil pumps are not so good either. I don't blame all this on GM/Chevrolet, as they have to meet very strict emissions and fuel economy standards by the year 2025.

Never would have though a Chevy Corvette would only come with an automatic transmission. with no stick-shift option, but it's here, thanks to those stupid regulations.

 

I agree with the corvette auto trans comment. Some people just want to shift their own gears.

I'm going to go with my first theory and hope the pump is ok and it's just an o-ring problem. My oil pan is leaking anyways and this is giving me a good reason to swap out gaskets.



I'm sure I don't need the racing girdle thing but it makes sense to me to keep any possible vibrations down in the future. I don't see how it could hurt. We'll see what happens when I get these installed.

 

Finally got around to pulling the pan to check things out. Found some sludge in the pan. Not sure if this is abnormal, but it looks like a lot to me.
I started to take the oil pickup tube loose from the back. After getting the rear two fasteners loose, the tube felt like it dropped. The O-ring ended up looking somewhat OK, but the bolt holding in the front of the tube is also tight... I'll see what happens when I finish cleaning up the parts today and reinstall them.

 

Some sludge is normal with longer than usually oil change intervals. I have also pulled them and they are as clean as the day they were assembled. If the pickup tube just kinda of feel out most likely the o-ring wasn't really sealing at all.

 

All better

 

Good deal.