Oil pressure drop 2007 Tahoe 5.3

[kingbeepa]

Over the past month, ‘07 Tahoe has had a low pressure alarm that indicates “Oil pressure low stop engine.” 240k miles. Oil level is full.

In response, I have correctly installed:
Oil pressure sensor, oil level sensor terminal connector, oil pick up tube assembly with new O-ring, oil reservoir gasket, and changed oil plus oil filter.

At least two things I have not addressed:
Oil level sensor, oil pump

As I’ve thrown a bunch of $$ at this mystery, which one of the two or some other thing should I begin with to get the warning alarm to stop?
What error codes would a computer likely tell me?

 

[wjburken]

Did you clean the screen below the oil pressure sensor?

Did you confirm oil pressure with an analog gauge?

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

First step is to purchase a mechanical oil pressure gauge, and they are available at Harbor Freight. Other folks here will chime in on exactly where to connect it.

This will tell you if your current pressure gauge is reading correctly or not, which is often the case in these situations. You can view the oil pressure with the accessory on with the motor off, the pressure at cold idle, the pressure at hot idle, and the pressure while driving (if you temporarily attach the gauge face to the windshield).

From there, there should be a straighter path to determining the source of your issue.

 

[kingbeepa]

Did you clean the screen below the oil pressure sensor?

Did you confirm oil pressure with an analog gauge?

Good things to consider!

There was no screen under the pressure sensor in the expected spot. Research turned up a common practice to remove the screen since they tend to clog. I was not surprised to see it missing and I did not install the one that came with the new one to stay consistent.

I have no analog gauge, but it sounds pretty straightforward based on research I’ve read.

To play devil’s advocate, what if these two leads turn up more failures? Go buy a computer reader? Change to a thicker oil?

 

[Marky Dissod]

If you use the engine during the winter, thicker oil is a liability.

Before addressing the oil pump, do a used oil analysis.
If it turns up too many wear metals, even a 'V4 mode' oil pump will only delay the inevitable at best;
better to start shopping for a 6.0L.
If the wear metals are low enough, then maybe try an oil pump used in V4 mode engines?

 

[wjburken]

Good things to consider!

There was no screen under the pressure sensor in the expected spot. Research turned up a common practice to remove the screen since they tend to clog. I was not surprised to see it missing and I did not install the one that came with the new one to stay consistent.

I have no analog gauge, but it sounds pretty straightforward based on research I’ve read.

To play devil’s advocate, what if these two leads turn up more failures? Go buy a computer reader? Change to a thicker oil?

Before you can move forward, you need to understand if you have a pressure generation issue or a pressure sensing issue. If it’s a pressure generation issue, you’ve already taken care of the most common issue which is the o-ring on the pick-up tube.

You already have a “V4” oil pump since your Tahoe has AFM. You may have a by-pass relief stuck open on the oil pump that is keeping it from producing pressure.

Find out if you truly have a pressure issue with an analog gauge and go from there.

 

[donjetman]

@kingbeepa
VLOM orings at towers may be leaking.

 

[strutaeng]

If not the VLOM, then most likely cam bearings or rod/main bearings.

My LQ4 had 260k miles when I tore it down due to a lifter tick. When it was cold (less than 40F) I would get the "low oil pressure" on the instrument cluster momentarily, then pressure would be okay. My cam bearings were kinda worn, but seemed typical. The rod/main bearings had minimal wear. I went ahead and replaced the cam/main/rods bearings since engine was torn down.

The oil pressure increased a little, but I haven't gotten the low oil pressure on start-up...well, it hasn't actually dropped to below 40F here yet. But oil pressure is usually "60" on the garage on cold start-up so I'm not expecting low oil pressure. I'm at 266k now, as a daily driver.

 

[j91z28d1]

confirm lack of oil pressure is real. if so, replace with high volume aftermarket pump. drive till blows up or you get sick or it. whichever comes first haha.


bit confused thou, is the low oil code being set all the time, or only sometimes? have you been driving it around with it saying pull over for lack of pressure.



yours sounds lower than most. but I've seen more than a few threads about low oil pressure. drop the pan to change o ring, new pressure sensors and stuff only to laster go back in for a high volume pump. no clue why it's still low, but the pump hides it and they don't seem to blow up soon after. so eh.