# Low oil pressure problem



## manfred (Dec 21, 2005)

Last year or so I have had this problem. 
At idle my '''low oil pressure ''' light comes on and I can hear some rattle.
2000 chev pu 5.3.
Would changing the oil weight help? Maybe 30 wt from 10w/30? 
Or 5w/20 from 10w/30?
Maybe I am overthing this heigher weight more pressure or lower weightm pump works better and builds higher pressure?
I am confident I'll get my answer here. Thanks


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## Old Vet (Oct 15, 2006)

manfred said:


> Last year or so I have had this problem.
> At idle my '''low oil pressure ''' light comes on and I can hear some rattle.
> 2000 chev pu 5.3.
> Would changing the oil weight help? Maybe 30 wt from 10w/30?
> ...


I don't know where you live but in Arkansas you can use 20w50 weight oil or straight 50 weight to have more oil pressure. Your main reason is that you need to have a crank job done on your motor. Your main bearings are worn out. But in order to have somebody to do it will be a problem because they want to put either a used motor in or a rebuilt one in.


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## manfred (Dec 21, 2005)

Im in okla. Soon to be warm weather here so I will probably switch to straight 30 wt.
It is worn out 250,000 miles.This has been going on for a year so maybe I will get by. Thanks


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## InvalidID (Feb 18, 2011)

I second the bearings going out. Sometimes (rarely) it'll be a plugged port or filter. If you are mechanically inclined I'd drop the oil pan next time you change the oil and see if the screen in the pan is blocked with sludge. I'm not sure how to check the bearings without taking one off sorry.

If the screen isn't sludged up I'd put in some 40w first and see if that does the trick. The heavier the oil the harder it is to get it flowing in the cold. If you don't get very cold where you are I'd do like OV said and go straight to the 50.


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## agmantoo (May 23, 2003)

I would put a true oil pressure gauge on so that I would know the oil pressure. I would want to know the oil pressure at idle as well as when the engine is revved at bit. The sending unit for the light could also be at fault. I have not owned a Chevy for sometime but I recall the light comes on around 7 PSI and that oil is bypassed at the oil pump around 35 PSI. I have known in older engines of folks increasing the bypass pressure to increase oil pressure. What weight oil and type has been used in the past?


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## Old Vet (Oct 15, 2006)

manfred said:


> Im in okla. Soon to be warm weather here so I will probably switch to straight 30 wt.
> It is worn out 250,000 miles.This has been going on for a year so maybe I will get by. Thanks


I have got more than that on my Chevrolet pickup and have good oil pressure. I would check the screen and if it is not blocked I would have a true oil pressure gauge to make sure that the sending unit worked like it is supposed to. You can get it done at most shops for little money before spend a lot of money.


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## Bandit (Oct 5, 2008)

The part that I would be concerned about was hearing a rattle at the same time as the low oil pressure light came on .
Heavier oil might quiet it a little , but not as a permanent fix , more as a fact finding mission .


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## Darren (May 10, 2002)

I had that happen on a diesel with less than 5,000 miles. Using a differnt brand of oil stopped the problem.


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## manfred (Dec 21, 2005)

The first time it happened is when In switched to mobile 1 10w/30. I moved back to dino oil and it cleared up for several months.


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## Gianni (Dec 9, 2009)

Pressure is resistance to flow. Your pressure is low because there is not enough resistance in your system. Your oil flows are insufficient to build pressure because of gaps in the bearing surfaces or the pump is not pumping its designed amount. Changing to a thicker oil may result in the gauge sensing adequate pressure but the bearing surfaces still not getting enough lubrication due to the thicker oil. Thicker oil may cheat the gauge but it will also cheat the engine. Time for a rebuild.


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## Darren (May 10, 2002)

manfred said:


> The first time it happened is when In switched to mobile 1 10w/30. I moved back to dino oil and it cleared up for several months.


I saw the same thing with Mobil 1. For some reason Mobil's Delvac synthetic didn't cause the same problem.


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## Wis Bang 2 (Jan 12, 2010)

What brand of oil filter? Some have cheap bypass valves and is known to make small block chevies rattle. Search around on a chevy board and you will see how this can be common.

AC, Purelator, Wix all have a better internal valve.

All I use in my chevies is Mobile 1 5w-30.

88 s-10 had 200K on the first engine and 100K on the crate when I sold it. The inside still looked like new. My Jimmy had almost 200K when I sold it. My Silverado is close to 100K. It is not the oil.


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## davel745 (Feb 2, 2009)

1 quart lucas oil additive


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## foxtrapper (Dec 23, 2003)

If you're rattling with 10-30, it'll really rattle with a 5-20. 

Go the other direction, say 10-40. or 15-40.


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## dodgetech (Jan 17, 2012)

Most likely a bad switch or "sendig unit" invest in a gage and check true oil pressure before worrying about it. Common problem on chrysler products is the connector gets oil, dirt, and moisture in it and causes the low oil light to come on also if it has signs of oil or any moisture in the connector use brake parts cleaner to clean it out then use die electric grease when you put it back together that is very common on chrysler and dodge vehicles.


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## kycrawler (Sep 18, 2011)

cheyv 4.8 5.3 and 6.0 mod engines use a bolt on oil pickup tube with an o ring to seal the pickup to the pump housing . The o ring fails pump sucks air oil pressure drops because of cavitation and aererated oil . This problem is sometimes compounded by sludge on the pickup screen . different oil isnt gonna fix it


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## farminghandyman (Mar 4, 2005)

Had the same problem when a cam bearing failed,


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## joejeep92 (Oct 11, 2010)

Thicker oil is not a solution. In fact it only deadens the sounds warning you of major engine damage. The thicker oil also increases damage due to dry starts in cold weather. Use manufacturer reccomended oil as that is what your vehicle is formulated to run best with. IN this case 5w-30. Thicker and thinner oil can cause other problems besides the one you are trying to remedy


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## haypoint (Oct 4, 2006)

Lots of "could be" solutions. 250,000 miles isn't worn out IF it has had an easy life with lots of oil and filter changes. 250,000 miles on a snow plow truck with few oil changes and you are on borrowed time.
Oil pressure drops due to worn oil pump is possible and once you drop the oil pan, an easy fix. As mentioned before, clean the pickup screen and replace the O ring where it goes into the pump.
Most likely, the oil pressure drop is due to worn bearings, creating added clearance between parts and the oil floods out. Could be fixed by replacing the main bearings, but it could also be the rod bearings. Somewhat less common, cam bearings can wear out. 

The pump picks up the oil in the pan and pushes it through the block, with "branches" at each bearing. When the oil pressure drops, the bearings farthest from the pump don't get the oil they need. Then you have accelerated wear. That could be increased clearance at the bearing or a hot spot that melts the bearing to the crankshaft, a spun bearing and a ruined block and damaged crankshaft. When the rod can not swing feely on the crankshaft, side pressure increases on the rod until it snaps. This allows the lower half of the rod to flail the inside of the engine block, often creating a "viewing port" in the lower portion of the engine block.

This accelerated wear can progress over months or a matter of seconds.


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## Bentley (Jul 10, 2008)

Gianni said:


> Pressure is resistance to flow. Your pressure is low because there is not enough resistance in your system. Your oil flows are insufficient to build pressure because of gaps in the bearing surfaces or the pump is not pumping its designed amount. Changing to a thicker oil may result in the gauge sensing adequate pressure but the bearing surfaces still not getting enough lubrication due to the thicker oil. Thicker oil may cheat the gauge but it will also cheat the engine. Time for a rebuild.


Gianni provides a really good description of what is most likely occurring. The rattle you are hearing is the sound of bearing clearance being taken up at each reversal. 

With perfect maintenance and an easy life, your engine might have a few more miles in it. Most likely, you will be needing a new engine soon.

How much oil does it use between changes? 

If the rest of the vehicle is in good condition, drop a new short block in, and have the heads rebuilt at a local machine shop. Or, buy a long block, and trade in the old engine.

My 2 â¬

B


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