Air in hydraulic pump at lines

So if all of the cylinders are fully extended, I would assume that the sump screen filter would still have to be completely submerged in oil to keep air from being sucked in through the top part of the cylinder-shaped screen filter? Which leads to another question, I'm wondering if I had a screen filter that was shorter then the one I have if that would give me more usable fluid in the tank? Also wondering how all of the metal filings in the screen filter before I cleaned it could have gotten in the screen filter when they are supposed to be heavier than oil and gather at the bottom of the tank?

Quite possibly could have been there since it was born. I agree, shorter filter would be better

Thank you so much for all this great advice.

So I have a possible solution to the filter sucking air. Instead of going with a shorter filter, I was thinking I might just put a 90-degree elbow where the filter attaches to the bottom of the inside of the tank which would put the filter horizontal about an inch off the bottom of the inside of the tank. And that would keep the same flow rate specs on the same filter . Your thoughts on that please? And if I do proceed with the elbow, I'm wondering what kind of material, plastic PVC would be the most economical, but I'm wondering if galvanized would be better and I'm wondering if it would not oxidize since it would be submerged by the oil and not exposed to air and water? if not PVC or galvanized, what other materials for an elbow would you suggest? I'm thinking brass, but that would be awfully expensive.

Plain old iron. No coating. NO PLASTIC!!!! It'll deform once it gets warm.
I would use a couple 45*s . Pressure, whether positive or negative doesn't like bends. Every 90 drops flow rate by a significant amount, I don't recall exactly but it's not good on the negative side.
Laying it over is not a bad idea. As long as overall height is diminished to achieve what you're after

Thanks so much! I will definitely take your advice. Seems like all I've seen at my local hardware stores is Galvanized, brass and PVC. Wondering where I would get just plain old iron, at a hydraulic shop?

You could try a hydraulic shop, farm supply, or home improvement stores. Hydro shop would be my last choice. They're gonna be the highest priced.
Maybe Google fastenal or motion industries.

Somehow this machine managed to run since 1980 without any troubles, but now you need to remount the filter/screen? Nothing has changed on the machine. I think you may be trying to reinvent the wheel here.

With the boom fully retracted, you should have the fluid almost to the top of the hydraulic tank, like 2-3" down in warm weather, a little more than that in cool weather 4-6" (warm weather makes the oil expand).

Don't go mixing around with the oil. If its ATF now, just leave it ATF.

With that screen pointing up on the bottom of the tank, it shouldn't matter if its completely submerged, as long as it can flow enough to feed the pump. If it was extremely clogged, it might not flow enough- get a new filter. But with the boom retracted- like it should be driving around- you should have all kinds of oil.

Ronray said:

. And it turns out that the tank has to be half full of oil to completely cover that sump screen filter.

Click to expand...

Your tank should be almost completely full of oil when driving around retracted. If you've only got a 1/2 to 1/4 of a tank of oil in it, as soon as you shoot out boom, the pump runs out of oil. Pumps starving for oil is really really hard on the pumps. Tank should be full with boom retracted. Don't trust the gauge, put a screwdriver in the tank to see how full it is.

Thanks for all that great advice! The 40 gallon tank only had 15 gallons in it so I went out and bought another 25 gallons. I don't know how old that 15 gallons was and if it was too thick to easily pass through the screen filter. So I'm going to drain out that 15 gallons, and add the new 25 gallons and see if that flows through the screen filter when the screen filter is not completely submerged and see if the pump still sucks air.

How did you get the screen out of the tank?

It unscrews. Since it is too hard to get a wrench on the bottom of the screen filter because of the curvature of the bottom of the tank, are used a rubber filter clamp tool like what you can get at Harbor Freight for a few dollars. The rubber strap will grip the screen without damaging it too much like a pipe wrench would do. You can also try to grip the very top portion of the screen filter so you're not damaging the screen pleats.

Bus, I also discovered that you have to have enough oil in the tank to keep the screen filter completely covered even when it draws down the oil level when various extension and lift cylinders are being filled with hydraulic oil. You can also experiment with the screen filter completely removed to see if that gets more flow to your hydraulic wheel Motors.