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Oil pressure problems. Any advice?

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Old Nov 11, 2016 | 08:57 PM
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Default Oil pressure problems. Any advice?

Hey everyone. I need some help trying to figure this out. When I start the car up is close to 60psi then drops to 40 at 160 degrees. Idles at around 20psi when full hot in traffic.

Now when throttle is applied driving around town it goes up to about 40psi but anything over half throttle or even at WOT it drops to about 10psi. At that time I left off completely and it goes back to 40psi. Hit it again and it drops to 10psi.

My friend said to change the opsu so I will do that first. But I'm fearing it may be the pump or a bearing. Any suggestions?

I'm thinking of changing the opsu first and take the intake off to see how much oil is passing through the intake and heads. Then I'll drain the oil and cut the filter. I didn't see any glitter from the dipstick but I'll be checking when I cut the filter.

Hoping it's nothing serious but I wanted to see if anyone encountered this.

Thanks!
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Old Nov 11, 2016 | 09:11 PM
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Is this a new build or just a new problem with an engine you've been running for awhile?
It's not uncommon for oil pressure to drop once you get some heat into the engine ( My truck does the same thing) but should not to lose pressure under throttle. My truck will also show better pressure for the first 1000 miles after an oil change then slowly lose pressure as the oil ages.
You might try adding an extra quart of oil to see if it helps the dropping pressure under throttle.
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Old Nov 11, 2016 | 09:14 PM
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Originally Posted by LLLosingit
Is this a new build or just a new problem with an engine you've been running for awhile?
It's not uncommon for oil pressure to drop once you get some heat into the engine ( My truck does the same thing) but should not to lose pressure under throttle. My truck will also show better pressure for the first 1000 miles after an oil change then slowly lose pressure as the oil ages.
You might try adding an extra quart of oil to see if it helps the dropping pressure under throttle.
this is an older engine. Bout 130k on it. It's a 98 ls1.
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Old Nov 11, 2016 | 10:18 PM
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I had a bad sending unit do it from vibrations at higher engine speeds. not saying it's case with you but maybe try another guage.
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Old Nov 11, 2016 | 10:21 PM
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Originally Posted by TurboTim
I had a bad sending unit do it from vibrations at higher engine speeds. not saying it's case with you but maybe try another guage.

if it makes any difference the gauge ticks at idle sometimes when sitting in traffic.
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Old Nov 12, 2016 | 08:12 PM
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Changed the sending unit. It doesn't drop to zero when at wot anymore but it's acting sporadic still at wot. Got a video. But don't think I can upload from my phone.
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Old Nov 12, 2016 | 08:26 PM
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Is the oil full?
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Old Nov 12, 2016 | 10:09 PM
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Eighteen year old pickup tube O ring ????
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Old Nov 13, 2016 | 03:20 PM
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Originally Posted by A.R. Shale Targa
Eighteen year old pickup tube O ring ????
For sure its time to replace stinkin oring!
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Old Nov 14, 2016 | 11:34 AM
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Originally Posted by RockinWs6
For sure its time to replace stinkin oring!

Well, I don't know when the pump was changed, if ever. Might as well do a cam while I'm in there. Oil is dark as coal. This all started after I changed the oil. Guess the previous owner was running thicker, conventional oil maybe. Switched to Mobil 1 5w30 this oil changed and pressure went wacky and oils is coal black. Going to drain and cut the filter to check for glitter and try and source an lq4/9 or lm7 shortblock at the same time.
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Old Nov 16, 2016 | 07:29 AM
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Check for air bubbles in the oil after the engine is hot. Turn off the engine and pull the dip stick and look carefully at the oil. If you see lots of tiny bubbles it a good bet the oil ring is just too deteriorated to seal. This can happen quickly after changing the oil as the new oil cleans everything in including the dirt around the oring that was helping to seal it. I personally would try putting 3 ozs of TransX in the engine oil. It won't hurt anything and if its the oring it may temporally patch it.

I've been doing this to mine for the last 50k but I think its time to change because its just too far gone. If you would see the factory oring you would understand why it needs changing. It wasn't made for this type of service in dirty acidy used engine oil. The new replacement orings are..........
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Old Nov 21, 2016 | 07:15 AM
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"and oils is coal black."
Depending on the miles on the oil, it could be due to excessive blowby.
Try a leak down and a comp test..
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Old Nov 21, 2016 | 09:31 AM
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Check with mechanical gauge to verify the issue.

I would then suspect the pickup tube o-ring as well.

My 170K mi silverado 6.0L
Green = Old
Red = New

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