Low oil pressure once warm????

[Lil-Pony]

84 2.8 b2
Once I've driven for a few minutes my oil pressure drops to like 5-7 psi while Idling
The engine was rebuilt a less than 10,000 miles ago and has been like this since I got it...
Is this a problem, I don't think the rebuilder did a true rebuild.


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[enginepaul]

The pressure drops as the oil get warm, but 5 to 7 is low. The gauge may be off is my first guess because an oil pump that works would give an adequate amount of oil for this engine. Also note that the volume of oil is more important than the pressure.
You might ask the rebuilder about this.

 

[Lil-Pony]

Cant ask the rebuilder since it was done 4 years ago but ive only put 10000 miles on her. Also the rebuilder went out of business for apparent reasons. Shity work

It may be 7-10 psi its hard to tell. Some time it sits at almost 0 while in drive siting at a light.

 

[wildbill23c]

I think it must be normal. I have a manual gauge in my 84 B2, and first thing in the morning when its cold I'm at about 40psi, after I've driven it around for a while (about 5 miles) the gauge has dropped to around 25-30psi, kind of hard to tell without taking my eyes off the road but at idle I know I'm between 20-30psi according to the gauge. I think these 2.8L's have a mind of their own anyhow.

I know when I first got my B2 last year and all the leaks it had, I think it was running around 5psi at idle. Now that I'm slowly getting the oil leaks fixed my oil pressure is kind of higher, I rarely see anything below 10psi now, occasionally it drops slightly below but that's after a 30 mile trip though, which after that I'm about a half a quart low on oil due to the oil leaks.

 

[Lil-Pony]

Well see i dont leak a drop nor do i burn any. It either the passages have been painted which i highly doubt. My oil pump sucks, i highly doubt, or my gauge is f*****d. On cold start my oil is 40-45psi but after a 13 mile drive its down to what i said.

 

[kimcrwbr1]

How old is the oil filter? I couldnt tell you how many times I run mine down to 0 due to oil leaks and still ticking. How hot is it getting will determine the oil pressure also. Since I fixed the leaks and put the thermostat in the intake manifold it rus cooler and has better oil pressure. I didnt check what model I got the thermostat housing but I think it was a B-II with A/C. It is a two piece housing with a 1 inch bypass nipple on it. I just plugged the 3/4 inch nipple on the intake manifold and put the thermostat up top.

You can kinna see it on the far right

 

[Lil-Pony]

I am due for an oil change. And i already have the therm up top. My temps run between 190-210

 

[RonD]

5-7 psi at warm idle is OK, low but OK to prevent bearing/engine damage.

It is odd on a rebuild with new bearings through.

Oil pressure is the back pressure as oil is forced out the bearing gaps, so not pump pressure.
As long as there is any pressure oil is lubing and cooling the bearings.
Valve train noise at idle would be when a real concern would be warranted, that would happen at about 2-3psi

As to why the lower pressure, oil distribution is like a soaker hose with alot of small holes in it.
As long as the Water pressure in the hose is above the amount of water that can pass out through the small holes water flows at each hole, thats back pressure.
If you were to make only one hole larger, then the back pressure at all the holes will go down.

So if the rebuilders failed to install the correct size bearing for the journal wear on one bearing then back pressure in the whole system drops.
So you have a "larger hole", but just guessing.

You can run a "thicker" oil if the pressure is a concern, 10-40 would be fine.

 

[Lil-Pony]

So a 10-40 will be thicker when warm

 

[RonD]

Yes the higher the second number the "thicker" the oil is at normal operating temp, 200deg.

Lower number is how the oil "thickness" will act at lower temps, below freezing.
So a 10w/30 will "act" like a 10 when cold, not be 10, just "act" like a 10, lol.

 

[Lil-Pony]

Can a overfilled motor cause running issues?

 

[dangerranger83]

When I had mine I put an hv pump in it. I had 25psi of oil pressure one warmed up. Got it to 80 one time on a cold day without it warming up and drive off but on a cold idle right after start up, 60 psi. This was running high mileage 10w-30 Pennzoil. Other then the oil pump, the engine was all stock and not rebuilt.

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[wildbill23c]

An overfilled engine can cause problems if it is severely overfilled, usually it ends up blowing seals and gaskets, can't remember off the top of my head what other damage it can cause, actually a form of hydrolock comes to mind as well.

 

[kennyjames]

It is normal for oil pressure to drop a bit when warm, as the oil viscosity drops some when hot, and the 'system' friction will drop a bit. It is not normal to drop to zero, which says you may have excessive internal bypass leakage - oil may not be getting to all your bearings, it is worth checking your filter to see if there is bearing material in the filter. and checking the oil itself for particulates indicating a bearing is going. As long as you can see reasonable oil pressure, a month should be OK, but I wouldn't try any long trips until you get the main seal changed...

 

[Lil-Pony]

It drop like a rock once warm and idling but, get the rpms to 1.5 and ive got 12psi. In the mornings i get 40psi. This is with the 10w40. Could the pump be going?