07 Suburban 5.3 with NO oil pressure

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My 07 Suburban with 158K miles usually runs 50-60 lbs of pressure at all times. The other morning I remote started it to warm it up for about 10 minutes. I get in and drive maybe 300 feet and the "no oil pressure, stop now" message shows on dash. I immediately turn the truck off. After a minute I restart and pressure goes to normal, so I head back to the house. Before I get there the pressure is back to zero. I park it and drive a spare vehicle.
That evening I check the oil and its less than a quart low. I start it up and it shows good pressure for about 5 minutes and then drops to zero. The oil (Mobil 5000) has 7000 miles on it and my filter is an AC PF48.
So I change the oil and filter and now have normal oil pressure.
Is the oil filter to blame?
 
Inconclusive. Did you hear any rattling?

Sending unit could be kaput too.
 
I seem to remember reading that the passage that leads to the sending unit can get clogged. Fine screen that gets covered with varnish, sludge...something like that. I happened to a coworker with an '07 Silverado, his local dealer put some sort of engine flush in the crankcase that took care of it.
 
Sounds like dirt blocking the meshfilter on the pick up tube on the oil pump. When you shut off the engine it drops from the meshfilter. And when you start it. After a while it cliffs again. I have seen the exact same symptoms on several engines.
 
Originally Posted By: eljefino
Inconclusive. Did you hear any rattling?

Sending unit could be kaput too.

No rattling even when I let it run a minute at 0 pressure.

Also, when I watched the needle it dropped to 0 in about 3 seconds. It was not an instantaneous drop from from 60 to 0, but a gradual drop.
 
Oil pressure sending unit issue. That's my bet.

Two things you can do:
1). Disconnect the OP sending unit harness and inspect and clean the electrical connection on both the harness and the unit. All auto part stores, even Walmart, usually sells an electronic connection cleaner is a bottle that looks like carb cleaner or brake cleaner. The electronic connection cleaner is good stuff. Use it.

2.) If that doesn't mix you problem. Replace the OP sending unit. Be careful not to damage the plumbing that connects to the sending unit. It might want to twist and bend fairly easily if the sending unit is being stubborn to remove.

Make sure you get an OEM unit. A real OEM sending unit. Amazon is a good source. If you don't, you won't be happy. Quality is [censored] and the chances of the unit giving you VERY different readings that your OEM unit did is very high.

You need to replace the unit, because on most GM engines, when the sending unit reads 0 pressure, it cuts the spark to the engine....and you're stuck.
 
I would cut open the filter and see. I have seen filters cause unexplained things before.

If it happens again, as another poster suggested, clean the contacts for OP sender and it it still happens, replace the OP sender.

You were due for an oil change anyway with 7000 on the Mobil 5000 oil.
 
Originally Posted By: Donald
I would cut open the filter and see. I have seen filters cause unexplained things before.

If it happens again, as another poster suggested, clean the contacts for OP sender and it it still happens, replace the OP sender.

You were due for an oil change anyway with 7000 on the Mobil 5000 oil.


I plan to hacksaw it open today. Yes, I was overdue for an oil change.
 
I did some web search on low oil pressure on a Silverado for a poster on another forum, and there is some kind of screen that can clog top rear of engine. Can't remember what the screen goes to.
 
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.
 
Start with the simple and verify the pressure. No knocking leads me to believe that it's a bad reading. Doubt very much that it's filter, as it would bypass. Could be pick up, but you don't know if the pressure is accurate.

Oh, and change the oil anyway.
 
I had the exact same problem with the exact same AC filter on my Sierra Denali pickup. I wrote about this several times. It happened to me with 2 different ac filters.

I stopped using them and problem never returned.
 
Last edited:
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.
 
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.

Bravo !!!!!
01.gif
 
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
 
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.


Too long, based on what?
 
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