Oil Pressure Woes - Need Advice/Help

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Kwing

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Folks, I got a heck of an issue and I'm plum out of ideas. I need some help in the worst kind of way. Sorry in advance for the length, but context and details is how you get to solutions, right? LOL

Bearing that in mind, I'll give the TLDR version first: My oil pressure sender has gone out before, I had a really bad overheating incident last year, followed by two minor overheating incidents, I suspect those incidents charred my oil and filled it with gunk, my oil pressure sender appeared to go out again, which I felt good saying it was due to that oil gunk clogging the screen, a month later it did it again, but I hadn't replaced the oil yet, so I did the oil and ANOTHER sender/filter last night, it worked fine, then oil pressure read zero again about an hour ago. I'm at a loss and need to figure out what to check and how to stop this from round 5!

Now the long version :)

I have an '07 Tahoe LT, 5.3 FFV, 285k on the clock.

End of 2018, my oil pressure gauge dropped to zero and the alarm started going off. There were no indications of low oil pressure other than the needle and alarm. I determined it was the sensor itself, swapped that out, problem went away.

A few months after that in March 2019, my AFM took a dump, and rather than a top-end rebuild, I opted to just swap out a full longblock. That was at 200k. Having recently survived the oil pressure sender, I replaced it again with the new engine, just to be safe (and so I didn't have to get up in that firewall again LOL).

Between then and August 2023, no oil pressure issues of any kind. In August, I was driving down the road fat, dumb, and happy, and a huge wave of "water" covered my entire windshield. The passenger side plastic end of the radiator had blown wide open. I had no clue it was my "water" until about 10 minutes later when the temp rocketed from 210 to past 3/4 over the course of about 30 seconds.

I replaced the radiator and all seemed well. A couple weeks later in the school pick-up line, the temp started climbing for no apparent reason. It was about a gallon low on coolant. I thought maybe I was just dumb and didn't fill it all the way, because I saw no evidence of a leak. When it did it again 2 weeks later, I looked a lot harder. Sure enough, there was a slow drip from the water pump. Probably popped a seal or plug when the radiator blew. So between then and December, I was just topping off the coolant every 4 or 5 days until I could afford a new water pump and have time to install it.

Middle of December, oil pressure dropped to zero. As with 2018's party, there were no indications pressure was actually low other than the needle and alarm. I checked the oil and there were chunks of gunk in it. I assumed it was charring from the couple of overheats. Ran a block tester to make sure the head gaskets were good, and concluded it was most likely the sender screen gunked up.

So I replaced the sender and screen again, and yes, the screen was all crudded up. And yes, the problem went away and I had normal oil pressure for a month.

BUT, my fat old a$$ stretching over the engine with a breaker bar for that job... Yeah... triple hernia (really bad umbilical and just normal bad bilateral inguinal). The ER visit to shove my intestines back into my stomach put a kibosh on the oil change and flush I planned after the pressure sensor.

Doctors ain't big on surgeries during the holidays, so I was put on light duty restrictions and scheduled for surgery last week. My wife picks me up from surgery, and I'll be damned, on the way home the oil pressure dropped to zero. I was thinking: "ok, I did this to myself by not doing the oil change."

About an hour after I climbed out of the anesthesia fog, my wife comes in and tells me there's a puddle of oil under the passenger side. Well it's had a rear main leak for over a year now, so some drips are normal, but puddles and being on the passenger side is not. So I hobbled out to the car and checked the oil. The oil was actually clean-looking, but at some point the spot welds on the dipstick tube apparently popped loose and the tube came out of it's hole in the block, puking oil in the process.

With a new, worse oil leak and a faulty reading from the gauge, I couldn't risk letting it wait for me to recover. So I did something SUPER foolish and called my brothers-in-law to come be my hands last night to replace the sender and screen AGAIN, do an oil change and flush, and replace the dipstick tube.

Ignoring that they somehow managed to break BOTH of the heater core Y-joints at the firewall clean off and then proceeded to break two spark plug wires and one spark plug getting the exhaust manifold lose, neither one of them felt like getting a triple hernia, so one of them brought my 16yo nephew to do the oil sender.

Despite confirming he had disconnected the harness, it turns out he dropped the socket over the sender with it still connected. It came out OK, but the socket severed the harness. Thank God I got the kit with the harness! LOL.

After getting the sender out, he went about trying to pull the screen out. After an hour and a half I'm like: "Dude, it's a PITA, but it ain't THAT hard". One of the tools he used was a long jeweler's driver to try and get it out. He claimed it just fell all the way in, like there was no filter there. So I found a "measuring" piece that was small enough to enter the top of the filter, but too big to get through the mesh opening at the bottom. It dropped all the way in too.

Having done it myself on one of the three previous swaps, we assumed he got it out and didn't realize it, threw the new filter and sender in, soldered on the new pigtail and went about fixing the rest of the crap they broke.

At 2am when we finally finished that mess, I drove it home and it was all good. Purred like a kitten and oil pressure was PERFECT.

About an hour ago, I cannot make this up, oil pressure dropped to zero AGAIN.

It now has a fourth brand new filter and sender, brand new oil, brand new filter, and had a chemical flush run on it before the oil change, and STILL it's acting up.

I'm at a loss now. There's still no indication the pressure is actually low, but even with not being able to inspect the old screen last night, I just have a hard time accepting it's clogged AGAIN.

What can I look at here? What can I check? This has to end! LOL!
 

j91z28d1

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where are you buying the sensors from?


you guys need to invest in a top side creeper. it's way cheaper than surgeries. crap.

is say it's 99% another bad sensor or screen. do a afm delete and you don't need the screen so you can toss it. put a oem from a dealership sensor in it.
 
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Kwing

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where are you buying the sensors from?


you guys need to invest in a top side creeper. it's way cheaper than surgeries. crap.

is say it's 99% another bad sensor or screen. do a afm delete and you don't need the screen so you can toss it. put a oem from a dealership sensor in it.
So I have a decent creeper, but you're gonna have elaborate on what an overhead creeper is. That's a new one for me, but a dang welcome one considering this circus! LOL

The sender in 2018 was an Autozone Duralast part. In 2019, it was an AC Delco from Rock Auto. December's came from Autozone again, last night's was from Amazon (money's pretty tight after having to meet my entire deductable and out of pocket max for the year last week... and a lot tighter after the $250 worth of collateral damage from last night LOL).

AFM delete was without question when I did the longblock in 2019, but with $3500 worth of engine and auxilary components, I couldn't afford a full mechanical/software AFM delete, so I did one of the OBDII dongles to just keep it from kicking on.

Is that a good enough "delete" to pull the screen, or do I need the full shebang?

I could see springing for a dealer sender IF I was 100% confident I wasn't headed for another rinse and repeat, but I gotta get that confidence at this point, LOL
 

j91z28d1

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I found my dealer would basically match gm parts direct or rock auto if I asked.. close enough for me to just get it local.

honestly not sure if just the afm blocker it enough. if you never plan to let it kick in, probably? it's meant to clean the oil headed to your afm solenoids and down to the lifters, if you never expect to open the solenoids, I don't see why it would hurt anything. but others might chime in with their thoughts.


top side creeper I couldn't live without working on trucks/suv. you can find them for about 150$ from time to time..

Img_2024_01_28_18_29_12.jpeg


I feel you on the first of the year insurance stuff.. ugh, it murders me every year for about 2 months till I hit the max out of pocket for the family and I can relax. I hate medical bills.
 
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Kwing

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I found my dealer would basically match gm parts direct or rock auto if I asked.. close enough for me to just get it local.

honestly not sure if just the afm blocker it enough. if you never plan to let it kick in, probably? it's meant to clean the oil headed to your afm solenoids and down to the lifters, if you never expect to open the solenoids, I don't see why it would hurt anything. but others might chime in with their thoughts.


top side creeper I couldn't live without working on trucks/suv. you can find them for about 150$ from time to time..

View attachment 420145


I feel you on the first of the year insurance stuff.. ugh, it murders me every year for about 2 months till I hit the max out of pocket for the family and I can relax. I hate medical bills.
With three ruptured discs from a stupid move a decade ago and now this triple hernia, considering 3 of the 4 vehicles I regularly work on include an '88 Suburban, a '58 Apache, and this Tahoe... that's a $150 I think I need to come up with.

If that stupid $0.99 nightmare is seriously for protecting the AFM lifters and not the sender itself, A, I'm'a be some kind of PO'ed at myself, and B, if I can verify those lifters don't collapse and reinflate under normal run/off cycling, I'm 100% onboard with your take. If they don't collapse (which the dongle has done well at ensuring that from an actual AFM command standpoint), a filter preventing them from clogging seems extraneous.

How do I determine for sure those 4 lifters only collapse under AFM command, though?
 

j91z28d1

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With three ruptured discs from a stupid move a decade ago and now this triple hernia, considering 3 of the 4 vehicles I regularly work on include an '88 Suburban, a '58 Apache, and this Tahoe... that's a $150 I think I need to come up with.

If that stupid $0.99 nightmare is seriously for protecting the AFM lifters and not the sender itself, A, I'm'a be some kind of PO'ed at myself, and B, if I can verify those lifters don't collapse and reinflate under normal run/off cycling, I'm 100% onboard with your take. If they don't collapse (which the dongle has done well at ensuring that from an actual AFM command standpoint), a filter preventing them from clogging seems extraneous.

How do I determine for sure those 4 lifters only collapse under AFM command, though?


ls engines without afm do not have the screen under the sensor. like my ls3 doesn't have one. of course the sensors are still junk and fail on everything but atleast one less thing to clog up.

as for how to prove your afm isn't activating. besides just not seeing it say 4 cyl on the dash or a scanner. I'm not really sure. I've seen some YouTube vidoes of a guy releasing them in hand with compressed air in the oil port.
 
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Kwing

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ls engines without afm do not have the screen under the sensor. like my ls3 doesn't have one. of course the sensors are still junk and fail on everything but atleast one less thing to clog up.

as for how to prove your afm isn't activating. besides just not seeing it say 4 cyl on the dash or a scanner. I'm not really sure. I've seen some YouTube vidoes of a guy releasing them in hand with compressed air in the oil port.
Oh I'm not worried about the status of their collapse function under operation.

My concern is that they would collapse when I shut the engine off, just when the engine goes into a resting state.

IF they do, THEN I'd be concerned pulling the filter as they could clog and fail to fill back up when I go to start and... 2019 all over again :)

Are there any professional writeups or resources that explain the nitty gritty function of the system so I could confirm they only collapse if the AFM valve body tells them too?
 

j91z28d1

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ahh yeah, you are always in 8 cyl mode except a few times when up to temp, running under a light load and light throttle. all other times the lifters are locked in normal mode.

this old video is pretty good at explaining it.


 
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Kwing

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ahh yeah, you are always in 8 cyl mode except a few times when up to temp, running under a light load and light throttle. all other times the lifters are locked in normal mode.

this old video is pretty good at explaining it.


That is EXACTLY what I needed to know! If they require positive pressure to collapse, they cannot collapse unless commanded.

You rock!

1000 thank-you's!

Now I just gotta figure how get it done without calling The Destruction Brigade, LOL.

I'm dang tempted to put an NPT to compression adapter back in that hole and run a 1/4" copper tube around to the front of the engine with a custom bracket bolted to the driver's side valve cover to mount the stupid sender up there.

Anyway, I digress.

THANK YOU!!!!
 

j91z28d1

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I've 100% wondered why they put it up there. there's at least 2 other places you could put a oil pressure gauge. the ls2 c5 had it above the oil filter I believe. but I guess with the afm being so oil dependent, it was the best place for it. I just wish they would have sourced better quality sensors. no other manufacturer I've ever been around has as many oil pressure sensor failures than a gm. and not just ls stuff, all the way back to the 90s gm struggled with failing sensors.. annoying at best.
 

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