GMC 5.3L Low Oil Pressure

[Wingman]

My son has a 2005 GMC pickup with a 5.3L V-8, with 180,000 miles. Occasionally, at idle, the oil pressure will drop almost to zero, and the oil pressure light will illuminate. I have been doing some reading, and it seems this is a common problem with this engine. Can someone give me some insight into this problem? I know that there are some engines that have very low oil pressure at idle and it is normal, for their engines.

1. Is this normal or harmful?
2. If this is not normal, what is the most likely problem?

This is a well serviced and maintained vehicle. I appreciate the help of the experts on this site!

 

[bubbatime]

Are you still running 5W30 oil? Perhaps try a 10W40 or 15W40 oil.

I had a car that would throw the low oil light on at idle with 5W20, but had good pressure with thicker oil.

 

[Wingman]

Have tried different oil weights, and it does not change anything.

 

[JHZR2]

Has a mechanical gauge been put on there? GM has "real" gauges, but theyre still probably based upon electrical sensors and signals...

 

[redhat]

Originally Posted By: JHZR2
Has a mechanical gauge been put on there? GM has "real" gauges, but theyre still probably based upon electrical sensors and signals...


This.

The oil pressure sender is on the top of the block just behind the valley cover. These are known to fail. However, I'm intrigued that it will show pressure at non-idle.

I'd say failing stepper motors in the cluster, but the fact that it illuminates the light ruins my theory there.

 

[sprite1741]

Gm sensors fail all the time. I am surprised it got 180k. You can get one at any auto parts store. It may have a screen under it. Just pull it out with needle nose pliers and clean it. Some idiot on Youtube posted a video of removing the screen with a pick and destroyed it. Don't do that.

 

[JMJNet]

Oil filter collapse internally?

 

[BigJakeChevy]

Originally Posted By: Wingman
My son has a 2005 GMC pickup with a 5.3L V-8, with 180,000 miles. Occasionally, at idle, the oil pressure will drop almost to zero, and the oil pressure light will illuminate. I have been doing some reading, and it seems this is a common problem with this engine. Can someone give me some insight into this problem? I know that there are some engines that have very low oil pressure at idle and it is normal, for their engines.

1. Is this normal or harmful?
2. If this is not normal, what is the most likely problem?

This is a well serviced and maintained vehicle. I appreciate the help of the experts on this site!


A few months ago i had similar situation. I replaced oring on the oil pickup tube. Cured my low pressure!

 

[SteveSRT8]

Oil pump pick up oring is a well proven cure. We have had one on a 6.0 that never had less than 30 psi on the gauge yet would occasionally clack the lifters at idle when hot.

We have an older (06) with almost 200k miles that runs low pressure. About 20-40 psi hot.

You also cannot trust the gauge until you verify it with a real mechanical one...

 

[Wingman]

Thanks, guys. The next step will be to hook up a pressure tester and see if it is just the gauge.

I assume that the pan will have to be dropped to replace the oil pickup "O" ring. Is that correct?

 

[Lubener]

Originally Posted By: JHZR2
Has a mechanical gauge been put on there? GM has "real" gauges, but theyre still probably based upon electrical sensors and signals...


Best advice to verify with mechanical gauge..I doubt Oil weight itself will not get anyone 0 lbs of oil pressure, your engine would be clanking if you had near zero pressure. and chances are just a sending unit is flakey.

 

[CKN]

The oil sending units go bad on these things frequently.

 

[Merkava_4]

Originally Posted By: BigJakeChevy
A few months ago i had similar situation. I replaced oring on the oil pickup tube. Cured my low pressure!


Originally Posted By: SteveSRT8
Oil pump pick up oring is a well proven cure. We have had one on a 6.0 that never had less than 30 psi on the gauge yet would occasionally clack the lifters at idle when hot.


Both you guys are lazy at writing the word O-ring!

 

[sprite1741]

Originally Posted By: CKN
The oil sending units go bad on these things frequently.


My original failed under warranty and the GM replacement sensor quit 2 years ago. Now I have Autozone with a lifetime warranty. I keep my 27mm sensor socket in the trunk so I am ready for it again.

 

[BigJakeChevy]

Originally Posted By: Wingman
Thanks, guys. The next step will be to hook up a pressure tester and see if it is just the gauge.

I assume that the pan will have to be dropped to replace the oil pickup "O" ring. Is that correct?

Yes sir! If 4x4 the front diff comes out as well!

 

[BigJakeChevy]

Originally Posted By: BigJakeChevy
Originally Posted By: Wingman
Thanks, guys. The next step will be to hook up a pressure tester and see if it is just the gauge.

I assume that the pan will have to be dropped to replace the oil pickup "O" ring. Is that correct?

Yes sir! If 4x4 the front diff comes out as well!

 

[Wingman]

Thanks, BigJake. Those are some GREAT pictures. The oil pressure has been normal all week on my son's truck. He is going to change the sensor this weekend. It will cost more to have the pressure checked that it will for him to buy a new sensor and install it himself. I will let everyone know the outcome. I greatly appreciate the replies from everyone!

 

[Wingman]

Well, it was not the sensor, and it does not have the screen below the sensor. So I guess the problem is the O ring or the oil pump. We will replace both and see if that solves the problem.

 

[ArrestMeRedZ]

I had this problem with my wife's company '05 Chevy 2500 with the 6.0. Took a while to find the right adaptor but was able to verify pressure was low at the sensor. Replaced the O-ring, cleaned the oil pump screen, and replaced the pump (requires removal of the timing cover and harmonic balancer in addition to other stuff on the front of the engine). Didn't help. Sold the truck as is. Last I heard it was still running.

 

[Wingman]

Yes. Trading it in is also under consideration.