loader bucket drops, before going up

RalphWD45

Well-known Member
I have a335 Minnie Moline, with a loader on it, The loader will pick up large round bales fine, and I can find no external oil leaks. when I hit the control lever, in the up direction, the loader will drop 5 to 6 inches, before it starts going up. I took the 2 spool control valve off, and took it to a hydraulic repair shop, and paid to have it rebuilt. After reinstalling the control valve, the thing is still the same. I changed the oil in the unit, and didn't find any water in the oil, and it wasn't foamy , like it had air in it. I refilled the loader with hydraulic fluid, ran it up and down, to remove air, and still have that small drop when I move the lever to up position. Is this a cylinder seal problem???
 
To see if it is the control valve reverse the hoses so up is down and down is up. if the problem goes away you know it is wear in the valve. Jim
 
Apparently, your valve does not have a reverse check valve in it. It takes a moment for the pump to build pressure equaling or exceeding the pressure that is holding the load up and thus the drop. Reversing the hoses is a good idea to try as it may just have a check valve in one direction. Note, a reverse check valve is not to hold the load , only reverse flow to the pump.
 
What brand is the valve? I had that problem with a Cross brand valve, contacted them and presto in the mail was a kit to replace a check valve. Fixed it! joe
 
Hard to tell if your valve has built in load check valves. Maybe ask the hyd. shop ? I think you can buy some from a place like northern tool or surplus center and install them in the hoses to the cylinders. Or just get a new valve with them built in.
 
You wouldn't want to put check valves in the hoses to the cylinders. Fluid needs to flow in both directions between the cylinders and the valve.

The check valve belongs on the IN side of the hydraulic valve, where the pressurized oil comes in from the hydraulic pump.

If you're using an aftermarket valve, no big deal. Just put a check valve in the hose leading to the IN port on your valve body.

Not sure when your Moline was made, but quite often on tractors built from the 60's on up, factory hydraulic valves are "hard plumbed" into the system, using hard steel lines or bolted directly to a ported casting. In those cases it's not simple or even possible to install an aftermarket check valve. There should be a factory check valve in the system somewhere.
 
I used the wrong terminology. I just went and looked at surplus center and they sell a pilot operated lock valve $ 104.95 sounds like it is designed to do what you need ?
 
lift cylinders are leaking ,,,my skid loader did the same thing rebuilt the lift cylinders and it fixed it
 

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