oil pressure drop

[Jworks]

2011 Sierra 4x4, 5.3 engine.  I bought from a dealer, used with 95k miles 2 yrs ago.  Dealer has been doing regular oil changes with Dexos synthetic.  No problems.  Now at 140,000 miles. Yesterday I notice oil gauge showing 21-22 psi at 2000 rpms.  I thought that seemed low.  At 3000 rpms it read about 27-28. Later that day started the engine again and this time the check engine light came on.  Drove 50 miles to a dealer and they said the scanner read "oil sensor, oil pressure , maintenance.  They said they'd start with the oil sensor, cost $350.  If that didn't work they'd proceed up the ladder to oil pump, if that didn't solve it then internal engine issue -- piston and rings replacement.  Is this a known issue with the 5.3?  Is it likely that its just the oil sensor or maybe sludge causing a clogged oil sensor screen??

 

[richard wysong]

piston and rings will NOT cause low OP , probably the orings on the pickup tube which has been discussed at length on this forum

[Jworks]

Thanks Richard Wysong.  I think the service dept guy was giving me a worse case scenario.  I'm taking it to an independent I trust.   Like you, I don't think its that severe either.  Probably, like you said, Orings or partly stopped up screen at the sensor.  I'll see soon.  Thanks

 

[dna9656]

$350.00 for a part that costs less than $20.00 and might take 15 minutes to install? I've done it, yeah it's a pain cause you can't see the sending unit without an inspection mirror but a competent mechanic could do it in 15 to 30 minutes. Suggest you find some one else.

Check my posts for comments on the "O" ring.

Edited April 6, 2022 by dna9656
more info

[Jworks]

dna9656, thank you.  I have it at an independent mechanic I know (and trust) right now.  Yes,  I know $350 was way too much, but that's what dealerships are like. 

 

Its at my mechanic's shop now.  When I drove it the 6 miles to that shop, the oil gauge was started off showing just shy of 40 for the first mile and half.  Then started dropping; the rest of that 6 mile drive was 28-30 psi at 1600 rpm.  Two days earlier it had been running 21-22 at 2000rpm.  So, maybe the o-rings, or sensor going bad and fluctuating, or the screen is partially clogged resulting in various readings.  Maybe oil pump is going bad.  Time will tell I suppose

 

Edited April 7, 2022 by Jworks

[richard wysong]

please post when you find the problem, 

[Jworks]

Richard wysong, an independent garage scanned it and put on a new oil switch.  [ I assume oil switch and oil sensor is the same thing ].  The check engine light is now OFF.  He said the screen was NOT sludgy.    I didn't think to ask if he used a GM switch.  I know he uses NAPA stuff often, as do most mechanics around here.

Yesterday I drove about 90 miles round trip at highway speed. At startup cold it was around 40 at 1100rpm.  At highway speed it was about 30 at 1600rpm (65-70mph).

This morning I decided to check it while I made the coffee.  Air temp is 41 (if that makes any difference).  At start up from cold @ about 1100 rpm gauge read 42.  Then after the engine throttled down from start up speed to idle speed, with idle @ 700 rpm its 40. 

Poured a cup of coffee, waited 5 mins and checked again (engine still warming up).  At idle its 30.

Went out 5 mins later.  Idle speed 700, oil gauge 28.

After 15 mins engine is warmed up, idle 700rpm, gauge 22.  I ran rpms up to around 1600 and hold there the gauge reads 30. 

So...I'm idling at 22 OP and highway speed about 30 on the oil gauge.  Is this enough??  Is 30 normal??. 
 

What do you think ?   I'll perform this again later in the morning after the engine cools down so I get a fresh start again.  I'll drive it and check it again.

 

Edited April 9, 2022 by Jworks

[richard wysong]

it sounds like theres still a problem, it still has enough pressure that it shouldn't damage anything yet. check DNAs posts for o-ring fix

[Jworks]

Richard Wysong, I agree with you, something still not right. 

UPDATE:  I was bouncing this off another friend in Canada.  He had the same thing happen.  He changed oil, using the same synthetic he'd been using but went with a higher grade oil filter than he'd been using.   He felt that the better quality oil filter made the difference.   His oil pressure went from 30 (highway) to 45 and 30 at idle.    It didn't make any sense to me; but I decided I'd try that. I put in Mobil-1 (the high mileage) 5w-30 and a Fram Ultra Senthetic filter.  To my surprise my highway speed is now 40-42 whereas it had been 28-30.  At idle pressure is now 30 whereas it had been 21.  I don't understand it but its fine now.

Edited April 10, 2022 by Jworks

[richard wysong]

yeah doesn't make any sense but hey as long as it works. Lots of companies make that dexos oil so I wonder what brand the dealer is using. they may buy it in drums or have bulk deliveries and possibly mislabeled

[Jworks]

I don't get it either.  Changing oil & filer makes no sense to me.  But it worked.  But it does make me think something to do with that batch of oil they used or the filter because right after I put in the Mobil 1 and a new Fram filter (for synthetic oil) it all changed.  I'm still getting usually 40 at highway speed and usually 30 idle.  Sometimes at highway I get 38-39 but usually 40.  Equally, I sometimes get 21 at idle but usually 30.  I don't know why that would differ.  I'm clueless.  The mechanic that changed out the sensor said the screen underneath it was clean as a whistle so he didn't replace it.  I kind of wish he had.  I'm happy with the 40 at hwy speed, though I wish the (sometimes) 21 at idle was better.  Like I said its usually 30 idling but not all the time.

 

Edited June 12, 2022 by Jworks

[Bleepster]

i had the exact same issue.  2011 Silverado, 5.3l - 110k.  i was at the upper limits of my mileage and ready for an oil change.  on start up id be at 42psi, as i drove it would hover at 22psi - not normal for my truck.  i had the oil changed and viola - back to normal.   sometimes the springs (valves) in the oil filter and go out, causing low oil pressure.  i believe this was my problem and possibly yours.

[Jworks]

Bleepster, I don't know what it was.  A member on this forum told me he had it years ago and just changed oil & filter.  He's made good suggestions in the past, so I figured what the heck I'll pay the $$ for the oil & filter.  Beats taking to shop and doing hit & miss.  And it worked for me.   Bleepster, does your idle psi vary at times like mine does?  (Sometimes 21, usually around 30)

Edited June 13, 2022 by Jworks

[Bleepster]

yes - mine varies at times - but usually hovers at 30psi

[newdude]

20 hours ago, Jworks said:

I don't get it either.  Changing oil & filer makes no sense to me.  But it worked.  But it does make me think something to do with that batch of oil they used or the filter because right after I put in the Mobil 1 and a new Fram filter (for synthetic oil) it all changed.  I'm still getting usually 40 at highway speed and usually 30 idle.  Sometimes at highway I get 38-39 but usually 40.  Equally, I sometimes get 21 at idle but usually 30.  I don't know why that would differ.  I'm clueless.  The mechanic that changed out the sensor said the screen underneath it was clean as a whistle so he didn't replace it.  I kind of wish he had.  I'm happy with the 40 at hwy speed, though I wish the (sometimes) 21 at idle was better.  Like I said its usually 30 idling but not all the time.

 

 

 

Filter.  We see them at work, they seem like they start to bypass early or are having an internal issue, and its worse on the longer oil drain intervals. 

 

Switch to the UPF-48R or PF-63 and you will greatly reduce and possibly never see an oil pressure issue down the road.