Loader bucket drifts down

I really couldn't decide what forum, to post this on, and tractor talk , seemed to be as appropriate as any listed. That said,, - my problem is that my lift cylinders, will very slowly drift down when they were supposed to be holding a load. A little history will now be given: This winter the loader would drop, seven to eight inches when I touched the control to go up. Not knowing diddley about hydraulics, I decided to have the giesen control valves rebuilt. I carried the valves into South Sound Hydraulics, and left them to be rebuilt, I then went home and drained all the milky oil, out of the resivour, hoses, and collapsed the two cylinders, to get any old oil from them. I refilled the system, with wally world Hy Tran oil. When I got my control valves back, I topped off the system, and raised the loader, to get all the air out, and the loader continued to have that big drop, when starting to raise it. I then decided it must be faulty lift cylinders. I removed the lift cylinders and carried them into Epic Industries, on the Tacoma tide flats, and left them to be rebuilt. When I got my rebuilt cylinders back, I installed them, and again topped off the oil, went thru the same raising and lowering act, to remove any air, and no longer had the dropping problem. I WAS HAPPY, I have been using it all winter, to feed big round bales with and felt good about it. Yesterday I used the loader to suspend, my ground driven manure spreader, so the wheels were about a foot off the ground. shut the engine off, and began working on the spreader, and within an hour, the spreader wheels were on the ground, a very slow down drift. Now I gave you guys all pertinate info, that I can think of, and hope someone, can tell me if the control valve rebuilder screwed up, or was it the lift cylinder rebuilder? Why is my loader bucket drifting down?

Keep going. You have a hydraulic leak somewhere. Eventually you will find the offending part. My guess is it's the hydraulic pump.

I had a similar situation with the boom cylinder on my Ford backhoe. Rebuilt the cylinder and it stopped drifting down for about a year. Now it's back to doing it again and I just let it drift. Not worth the PIA of taking that cylinder apart again.

Had a problem like your earlier one on a new New Holland skid loader. Boom would drop when you went to raise it. It was a bad cylinder.

I imagine your problem now is a cylinder. I think the only way you're going to isolate it, is to isolate it! It's a messy proposition- undoing lines/fittings, and capping, or whatever you have to do to isolate different parts of the system.

About the simplest test you can do is raise the loader up with a load on it, shut off the engine, disconect the pump and return lines from the valve.

If fluid is coming from either fitting, try very carefully moving the valve lever in both directions to see if you can stop the flow. If you can, there is a problem with the centering of the valve.

If no fluid is getting by the valve, and the lift is creeping down, there is a bad cylinder seal.

Since there are 2 cylinders, you will need to disconnect the hose that raises the cylinder from one side, cap the line, raise the lift and see if it creeps down. Repeat for the other side. Messy, but the only way to truly test the seals.

Your loader may be OK as-is, check your operator's manual. Most hydraulic loaders were never intended to hold a load indefinitely without very slowly drifting down. It would be safer and more reliable to use the loader to lift the speader onto blocks and then work on the speader while it is on blocks.

RalphWD45
If control valve has no external leaks then valve rebuilder is not at fault because that's all that can be accomplished by rebuilder short of replacing spool & valve body with a new complete hyd valve IE spool & valve body must be replaced as a set.

I think that's the best you can expect out of old, worn equipment. Even "rebuilt" they will not seal perfectly anymore because... they're old and worn!

Rebuilding entails taking the valves and cylinders apart, looking for excessive wear and/or scoring, then replacing o-rings, packings and gaskets. That's it. Anything else would be big-bucks machine work, and it would be more economically sound to simply buy new valves or cylinders.