Low Oil Pressure at Idle

[Nicolai8775]

The question about using a cylinder compression tester to check oil pressure is what threw me.

If that sender is wet, that is where to start.

I just didn't want to buy a new tester gauge lol.

 

[OR VietVet]

You can rent them.

 

[Nicolai8775]

You can rent them.

Yes! Good to know. So should I grab the Delco and wait for shipping or will the O'Reilly's special be adequate? The ones on O'Reilly's show a screen included with the switch. From what I've read the screen wasn't there pre 2007 models, is this correct?

 

[Fless]

Start at the top of the engine and work downward, inspecting all over for any possible oil leaks. Pay close attention to the top of the block behind the intake manifold; there you'll find the oil pressure sender and the camshaft position sender. Also, the valley pan cover under the intake can leak back there. Valve cover gaskets are another source, and all of these can leak down the back of the block and look like a main seal leak. There's an inspection window on the bell housing, you can carefully inspect inside of it for a rear main leak, but you might need an endoscope to confirm.

No screen on the oil pressure sender on a 2006 or earlier; those screens came with AFM.

 

[Nicolai8775]

Start at the top of the engine and work downward, inspecting all over for any possible oil leaks. Pay close attention to the top of the block behind the intake manifold; there you'll find the oil pressure sender and the camshaft position sender. Also, the valley pan cover under the intake can leak back there. Valve cover gaskets are another source, and all of these can leak down the back of the block and look like a main seal leak. There's an inspection window on the bell housing, you can carefully inspect inside of it for a rear main leak, but you might need an endoscope to confirm.

No screen on the oil pressure sender on a 2006; those came with AFM.

See I was kinda overthinking everything. Very good suggestion. Thank you!

 

[OR VietVet]

Yes! Good to know. So should I grab the Delco and wait for shipping or will the O'Reilly's special be adequate? The ones on O'Reilly's show a screen included with the switch. From what I've read the screen wasn't there pre 2007 models, is this correct?

I only trust the GM/AC Delco parts for my rig. They got that rig 135k miles and there is a reason why. Yes, as @Fless said, do a thorough inspection and there is no screen there.

 

[Fless]

As far as oil pressure is concerned, as @PNW VietVet mentioned, getting a manual gauge on it will confirm or dispute the gauge reading.

 

[Nicolai8775]

As far as oil pressure is concerned, as @PNW VietVet mentioned, getting a manual gauge on it will confirm or dispute the gauge reading.

Alright I'm gonna get it done. Thanks!

 

[Nicolai8775]

Weird. I started tearing into it. The plastic retainer clip thing was broken off on the connector. So somebody has already replaced this at some point I'm guessing. I'm going to the scrap yard tomorrow to grab a few different switches to try, but I suspect that it's the O-ring. I did take the sensor out with the 1-¹/¹⁶ socket. What a bastard that was. Finding the hole and putting the replacement in is going to be fun lol.

O'Reilly's doesn't have a oil pressure tester but AutoZone and Napa does, I'll stop there tomorrow.

By the way, this suburban has 322,000 miles on it. Really hoping it's not bearings lol

 

[swathdiver]

So when I bought this truck, a 2004 z71 Suburban, I noticed the pressure was just a little bit lower than the "normal" pressure than on my old Tahoe.

I changed the oil and filter with Royal Purp 5w-30 and a WIX. It raised the pressure back up to where it should be. 40 at idle and 45-50 when I press the throttle.

I've driven 3,000 miles already cause I road tripped to Idaho. I'm assuming the oil is less viscous now, but the oil life counter on the dash says it's at 50%. At idle I get 25psi, at throttle I get maybe 40psi. I had read somewhere that it should be 10psi per 1000 rpm. If this is true I'm still in the acceptable range. But I don't like it cause it's not normal.

2 questions. Is this the O-ring issue on the pickup tube? Or could it be the rear main seal, I have some seepage on the backside of the pan where it meets the trans and some drips on the driveway. Does the rear main seal being broke affect oil pressure to the degree that I'm seeing? Maybe I have both issues.

I don't hear knocks, on a cold start I sometimes hear what I'm guessing is a lifter tick. It goes away within minutes of startup. I hope it's not a bearing lol

Normal, no I'd say it's great oil pressure for 322,000 miles! Now if it bounces up and down a lot, then I'd say it's the pick up tube o-ring and you can eliminate that by adding 2 additional quarts of oil and idling the motor to see if it stops. Oil pumps can wear out and bearings can too of course, the cam bearings are the usual culprits,; the first of the bearings to go that is.