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Low oil pressure


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I just bought a 2005 4.8 Sierra xtra cab, after driving a Ford Ranger(Mazda B4000) for 20 years. One thing I noticed when I test drove it was the oil pressure guage was stuck at 80lbs. I did not think anything of it except I figured the pressure sensor would most likely be the culprit. Otherwise I thought it drove great. Today I bought a Standard Ignition brand sensor from Oreillys that had good reviews. Once I got it home I noticed it did NOT come with a crusher washer but a washer with a rubber inner that pushed over the threads. I double checked with the picture on Oreillys and it did show a crush washer. I was like oh well I will put it on It should work -the old sensor was leaking. Once installed, I turned on the car and the oil pressure went to 0. I drove it up the street and the highest it went was 20 psi. About an hour later I drove just over 1 mile and the low pressure warning popped up. I am a bit nervous here. Like I said it ran fine and runs fine even now(drove about 20 miles earlier before the switch out)- no smoke, noises etc. There is some oil on the bottom of the engine.

The car has 135, 000 miles and seems to have been well taken care of, but who knows. It had no previous records. Could it be that it is not really crushed on the car and that is what is helping to cause the low oil pressure? I read of certain oil filters that can cause low oil pressure. This is an Omnicraft (ford brand?)oil filter. Any help, advice would be great. 

 

Mark

Edited by Mark4000
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Thanks for the quick reply! 

I Changed out both sensor and filter( both ac delco). No change. I drove to max running temp then low pressure warning light came on.  
 Also, engine light came on while driving but right when I got back to my house after the 5 mile drive it went out. It is on again and confirmed with a cylinder 3 misfire.

Edited by Mark4000
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Get a hold of one of these bad boys and an oil pressure gauge set.  

 

Amazon.com: OTC Tools 7219 Oil Pressure Adapter: Automotive

 

You will want to know the mechanical pressure of the engine.  This adapter above will let you test pressure straight off the pump.  

 

If you wanted to test it up top as well, get one of these:  LS1 LS2 4.8 5.3 6.0 Oil Pressure Sensor Gauge Adapter Fitting Engine Swap Copper | eBay

 

I would not rely on the sensor or the gauge on the cluster seeing you went from stuck on at 80psi to now no or very little oil pressure.  

 

Potential causes?  Bad oil pump or bad oil pump pickup tube o-ring. 

 

 

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5 hours ago, newdude said:

Get a hold of one of these bad boys and an oil pressure gauge set.  

 

Amazon.com: OTC Tools 7219 Oil Pressure Adapter: Automotive

 

You will want to know the mechanical pressure of the engine.  This adapter above will let you test pressure straight off the pump.  

 

If you wanted to test it up top as well, get one of these:  LS1 LS2 4.8 5.3 6.0 Oil Pressure Sensor Gauge Adapter Fitting Engine Swap Copper | eBay

 

I would not rely on the sensor or the gauge on the cluster seeing you went from stuck on at 80psi to now no or very little oil pressure.  

 

Potential causes?  Bad oil pump or bad oil pump pickup tube o-ring. 

 

 

Thanks for the reply. So the first adapter from Amazon screws into where the oil filter goes and the filter goes on top of this?

 

On the second one, wouldn't a pressure tester kit come with an adapter or just plug the  guage right where the sensor goes?

I saw how the adapter from Amazon works. Will get it tomorrow.

Edited by Mark4000
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13 hours ago, Mark4000 said:

Thanks for the reply. So the first adapter from Amazon screws into where the oil filter goes and the filter goes on top of this?

 

On the second one, wouldn't a pressure tester kit come with an adapter or just plug the  guage right where the sensor goes?

I saw how the adapter from Amazon works. Will get it tomorrow.

 

The first one you take and leave the oil filter off.  

 

The adapter probably comes in a kit?  Not sure.  

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Never got the gauges but did have my mechanic drop the pan and replace the gasket(oil leak) and oil oring. Pressure more than doubled; now 21 at hot idle and 40 at full temp. 

Unfortunately the tech found a layer of 3 mm of shiny/glittery metal(not chunks) at the bottom of the pan. So some sort of engine wear. 

 

Also, changed the spark plugs. Terrible! The worst one is not even in the picture. But the good looking one was just from 10 miles of driving. I wanted to change it because I had a cylinder 3 misfire-it was before I took it to the mechanic. Now After driving 40 miles no codes came up or no low pressure warning. I did put in a can of Techron in my tank. Will clean the throttle body next.

 

20210424_140549[1].jpg

Edited by Mark4000
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