07 Suburban 5.3 with NO oil pressure

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There's a lot of nonsense in this thread.

One, that is definitely not an excessive interval unless an OAI shows some sort of specific issue related to the driving patterns. The OLM is calibrated for quality Dino. Use a Dexos labeled oil for extra peace of mind.

Second, the PCM in the engine will automatically pull the spark signal if the oil pressure drops below a certain value, like 6 psi or so. The engine will not run.

Note that rear main seal leaks have not been a problem in our fleet GM V8 vehicles since the introduction of the Vortec series engines LOOOOOONG ago, it just doesn't happen even after 2-300k miles or more...
 
I have never heard of any GM V8's having rear main seal problems in the past decade.

A lot of info on here pertains more to the 90's and 80's. Like the intake manifold gasket issues GM V6's used to have back in the 90's. People forget that was 14+ years ago now!
 
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Well, it happened again. A few days ago my wife calls me and said the no oil pressure warning light came on again. She shut it off immediately. It has been 4000 miles since I changed the oil and filter (PF48) when I had the problem before.
I grab a new oil filter (another PF48, it's all I had)and wrench and head that way. When I get there (20 minutes later)and start it up, it shows good pressure, so I drive it towards my work which is about 1 mile away. Half way there the pressure is dropping. As I pull into work the pressure hits 0 and I shut it off. I immediately change the filter only and then immediately start it back up. Maybe 4 minutes between shutdown and restart.
Pressure is normal and I have drove about 400 miles on the new filter and old oil with no pressure problems.
I plan to change the oil and filter today.
 
Originally Posted By: bama7x57
Well, it happened again. A few days ago my wife calls me and said the no oil pressure warning light came on again. She shut it off immediately. It has been 4000 miles since I changed the oil and filter (PF48) when I had the problem before.
I grab a new oil filter (another PF48, it's all I had)and wrench and head that way. When I get there (20 minutes later)and start it up, it shows good pressure, so I drive it towards my work which is about 1 mile away. Half way there the pressure is dropping. As I pull into work the pressure hits 0 and I shut it off. I immediately change the filter only and then immediately start it back up. Maybe 4 minutes between shutdown and restart.
Pressure is normal and I have drove about 400 miles on the new filter and old oil with no pressure problems.
I plan to change the oil and filter today.


Cut that filter open and inspect.

edit: You said you were going to cut the last one open too... What did you find?
 
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It's not the oil. It's not the filter. It's not the sending unit. It's not the engine.

The oil galley that feeds the oil pressure sender also supplies oil pressure to the AFM Valve Lifter Oil Manifold (VLOM). The four solenoids that control the AFM activation are fed oil through the VLOM. Because of the delicate nature of the small solenoids, a small fine-mesh screen is inserted into the oil tally that feeds the VLOM, just below the oil pressure sending unit.

That is clogged.

Remove the sending unit. Look into the oil galley where the sending unit was removed from. You'll see the screen. You can't miss it. Remove it and clean the screen with some brake clean and reinstall it. If you'd prefer, go talk to the parts counter at the local Chevrolet dealer. They'll know exactly what you're talking about and likely have a new one in stock.

Buy me a beer next time you see me.
 
My GM 6.0L doesn't have AFM but I had the same issue...happened twice both times an AC DELCO PF48 filter. I never used them ever again and never had the issue ever again.
 
Like I said before it seems like an electrical problem. If you really lost oil pressure the lifters would be ticking away.

Also like I said before mechanical problems don't heal themselves. If you lose oil pressure mechanically it will still be 0 after you shut it down and restart it, and it will still be 0 after you change the oil and filter. In the time from your first post to this one the motor would have seized.
 
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Originally Posted By: Luber216
First of all, you're going entirely too long on conventional motor oil. I'm surprised it was ONLY less than a quart low. Less than 5 quarts in your crankcase technically doesn't read on the dipstick even though there's some at the end. Does your rear main seal leak. It's a very common problem with GM V8s. Another common problem with GM vehicles is the gauges becoming non-functional and the sending unit going out.



You can't be serious. Why exactly is his interval too long.
Unless there is some kind of issue with the engine or its short tripped there isn't anything wrong with his interval.
I notice you're new so I'll extend the bitog welcome to you and suggest setting aside some time to read the articles on the bitog home page. Read ALL of them and if you've got any questions just ask.
Absorb the info gleaned from the articles,then post from the knowledge learned.



Originally Posted By: OVERKILL
Originally Posted By: Phishin
Originally Posted By: NHGUY
If its a dirt/sludge
problem,might want to switch to PYB/PP/PU.


I was waiting for this......the biggest myth on BITOG. Everytime I read this line of [censored], I wanna choke someone.

"You got a dirt/sludge problem, do ya? You should run some PYB/PP/PU"....Is Pennzoil's marketing really that good?

So tired of this recommendation based on absolutely NOTHING. I'm sure dang near any oil will clean just as well as Pennzoil products, including, but not limited to: M1, Valvoline, Super Tech, Quaker State, Castrol, etc. etc. There is nothing special about Sopus and cleaning up an engine.

Please stop perpetuating this non-sense.


LOL! So true!
thumbsup2.gif




Hehehe. Shows at least some of pennzoil's marketing works at least.
This pennzoil cleaning stuff bothers you guys as much as people pushing that conventional is shot at 3000 miles.
Some folks believe the commercials and salesman and just follow their suggestion without a second thought.
Kinda reminds me of the guys who pitch a premium oil filter at 5000 miles because of the "one filter,one oil change interval"nonsense.
Some folks can't be taught no matter what facts stare them in the face.

OP. It could be a lot of things. Try the sending unit first. If its fine then we can eliminate it.
Then I'd try a can of sea foam in the oil to clean up the pick up screens so I could cross them off the list.
Keep eliminating potential problems until you've found the issues.
 
Originally Posted By: hattaresguy
Like I said before it seems like an electrical problem. If you really lost oil pressure the lifters would be ticking away.

Also like I said before mechanical problems don't heal themselves. If you lose oil pressure mechanically it will still be 0 after you shut it down and restart it, and it will still be 0 after you change the oil and filter. In the time from your first post to this one the motor would have seized.


While your logic is correct - in my case I had no oil pressure at start up with an AC filter. Changing the filter solved the problem both times. Both times AC filters. 30k miles later and on Bosch filters I never had the issue again. I truly believe, in my case, it was the AC filters.
 
That seems like strange behavior for a failed sending unit.

My first move would be to hook up a functional oil pressure gauge and compare the readings.
 
Change out the oil pressure sending unit. 11 bucks at Autzone. Back of the engine between the heads. I have had a 5.3, 6.0 and three LS1s. The failure of the OPSU is common.
 
Originally Posted By: hattaresguy
Like I said before it seems like an electrical problem. If you really lost oil pressure the lifters would be ticking away.

Also like I said before mechanical problems don't heal themselves. If you lose oil pressure mechanically it will still be 0 after you shut it down and restart it, and it will still be 0 after you change the oil and filter. In the time from your first post to this one the motor would have seized.


I only let it run at 0 pressure for a minute. Talking with several people, they say it usually takes 2-3 minutes for the lifters to start ticking.
Do you feel it's physically impossible for an oil filter to cause a 0 pressure situation?
If it's the sender, then why would changing the filter immediately fix the problem...twice
 
Changing anything can spike the pressure to the OPSU and alter its reading.

Oil pressure related failures are EXTREMELY rare. The far more likely cause is the sender or the associated wiring.

FWIW there is more than one anyway, and the PCM will pull the spark if OP is zero...
 
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