Low Oil Pressure

[estone4009]

I have a 1999 5.3L silverado. The idiot light keeps coming on saying I have low oil pressure when you go to a stop in the truck. The gauge on the dash reads about 2psi. I know the mimimum is 5psi. This truck had both head gaskets replaced several months ago for a coolant leak internally and at the same time the oil pressure sending unit was replaced. Does anyone know the easiest way to put a mechanical gauge on the truck without having to remove the intake manifold? The oil sending unit is on the drivers side up next to the firewall. Here are possible causes I've been given:

dying oil pump
clogged oil pickup screen
loose oil pickup screen

This truck has 85000 miles on it. Would I be better off to do a junkyard engine swap or just trade the headache in?

Thanks,

Eric

[broughy84]

OR your bearings are shot from the antifreeze oil mixing. Is the truck knocking or anything. 2 psi IS LOW. DANGEROUSLY LOW. I would put some 20W50 in that baby and trade-er in, let the dealer figure it out.

[gtmud]

Depends how involved you want to get. If the truck has been good to you, and the body and drivetrain arestill in good shape, I would take the extra time and do one of 2 things, First put the mechanical guauge on it, if still reads low, good chance that your bearings and or pump are gone. Pull the engine, send the crank into a shop to be turned and replace your rod and main bearings along with the oil pump and pick-up tube. It sounds like a lot, but from experience this works, and you'll get MANY more miles out of your truck. Inspect your bearings, and crank BEFORE you pull the engine. You might be able to get away with just replacing the beaings and oil pump, and not have to pull the engine. Good luck.

[estone4009]

Is it possbile to put a mechanical oil sensor on without removing the intake manifiold? And is it possible to change the oil pump and pickup screen without pulling the engine? I was under the impression that you could not get to the oil pump any other way.

[gtmud]

It depends how things are set up under neath the truck. If it looks like you can remove the pan , then you might have to raise the engine to get the pan to clear the engine, ie. unbolt the mounts and jack the engine up enough to clear the pan.
Do you hear anything when the engine is running, rod knock? I would do everything possible to put the mechanical guage on to double check your oil pressure, BEFORE you tear into the lower-end. If you have to redo the lower -end, do EVERYTHING. Don't skimp, you want to do this once, not twice. Replace your bearings and if it needs it, turn the crank. then you won't be worrying about if it will work or not. I have a 91' 4.3 w/160K+ on the original oil pump, more than likely your bearings were washed out, so just changing your pump probably won't fix the problem.

[jeverett]

Mine just did this, EXACT same problem. I had the head gaskets replaced b/c of an internal coolant leak, and 20K miles later, the engine locked up completely, but I still had abotu 30 psi of oil pressure.

[estone4009]

Did you fix the engine or just put a new one in? Did you ever determine exactly what caused it?

[nineball481]

Originally Posted by jeverett

Mine just did this, EXACT same problem. I had the head gaskets replaced b/c of an internal coolant leak, and 20K miles later, the engine locked up completely, but I still had abotu 30 psi of oil pressure.

jeverett- I just bought my truck last March. Ive been looking through here to see at what mileages things are going out.... Do you know what mileage you had on the truck when you had the internal leak fixed?

[nineball481]

I currently have 52,000 on my '00. I understand that a lot of u-joints go out around this time....

[estone4009]

My leak started at about 75,000 miles.

[jeverett]

It was about..72K to be exact. It had leaked 3 coolant bottles into the oil, and I never could find it, until I changed the oil. I had new head gaskets put on, and all was well until 96K, when I spun a rod bearing racing someone, and a week later the engine locked in the middle of an intersection. I had the whole engine replaced with one from a salvage yard that had been rear-ended and totalled w/ 55K on it Got that engine in w labor and everything was $2500..waaay better than the 7000 the dealer wanted.

[estone4009]

I put a mechanical gauge on it and it idles at 5psi and NEVER goes about 25psi at full throtle. I know it is a matter of time before this engine goes. If it was your truck would you get the engine rebuilt or just trade it in to a unknowing dealer?

[broughy84]

5 is a little to low. I would get a thicker oil in it, it will make it last a little longer.

[gtmud]

5 PSI!! Don't drive it!! Open it up, and spend a weekend replacing the bearing s and oil pump/pick up tube. You can do this in your driveway IF your careful! Or pull the engine, remove and turn the crank then all the other stuff(bearings, oil pump).

[estone4009]

Does the engine have to be pulled to do that? Or can it stay patitaly installed?