Weak Loader; won't stay lifted.

[Zete]

Hello all,
I own a 1996 50th Anniversary Zetor 4320. Runs like a sewing machine in a tub of warm butter. Anyway, the Bush Hog 2445 QT loader has been getting weaker with time, doesn't want to stay lifted unless I hold the stick down and rev the engine. There are no visible leaks on the cylinders. Reservoir is full of hydraulic fluid. . What should I check first? Thanks

 

[rScotty]

If the cylinders aren't leaking externally, it's not the cylinders. And if the reservoir is full of decent hydraulic fluid, and the fluid doesn't look to be full of water or air bubbles then it's not the fluid. AND if the loader has good power but just isn't staying up then it isn't the hydraulic pump.

So if given those things I'd check on a getting a replacement for the directional control valve assembly - that's the spool valve assembly with the levers. They are universal, not too expensive,and are not rebuildable. Most droopy loaders are simply from wear in the spool assembly. That doesn't mean that is the only cause, just the most likely. My guess is the Bushog uses a very standard size.

Otherwise, if you want to do some tests you are going to have to get creative. Figure out a way to block the hoses into and out of the directional control valve. That would be a good way to start.
Just so you know,

Hydraulics | www.surpluscenter.com

Hydraulics,Hydraulic Cylinders,Log Splitters and Components,Hydraulic Motors,Hydraulic Pumps,Hydraulic Valves,Hydraulic Power Units,Hydraulic

www.surpluscenter.com

That location will get you started. There are lots of brands, most of what they handle is overstock. Mountings on control valve assemblies are pretty universal. If you need Power Beyond, get it when you order. Otherwise all you need to match are GPM and thread type.
rScotty

 

[BeezFun]

Switch lines with the bucket curl hoses. If it lifts properly it's not the seals. That would point to a problem with the valve, you could do a few more tests to be sure.

 

[Tx Jim]

Ditto what rScotty stated boom cylinders aren't the problem if they're not leaking externally around rod seal but control is leaking internally.

 

[BravoXray]

Hello all,
I own a 1996 50th Anniversary Zetor 4320. Runs like a sewing machine in a tub of warm butter. Anyway, the Bush Hog 2445 QT loader has been getting weaker with time, doesn't want to stay lifted unless I hold the stick down and rev the engine. There are no visible leaks on the cylinders. Reservoir is full of hydraulic fluid. . What should I check first? Thanks

One or both the cylinders are leaking past the piston seals. Very rare to have a control valve leak internally.

 

[npalen]

The loader boom won't drift down even if the piston seals are bad unless the valve is leaking by internally.

 

[oldnslo]

One or both the cylinders are leaking past the piston seals. Very rare to have a control valve leak internally.

If the cylinders are leaking the oil still has to go through the valve to allow the loader to drift down. It is totally possible and likely that a cylinder is leaking but the flow still has to go through the valve. A couple simple tests are:

like others have recommended switch hoses to the curl circuit and see if the drifting slows or stops and does it lift normally with reving the engine?

another option is to Jack the loader up disconnect the quick disconnect on the cap end and then remove the Jack. If loader now drifts down the lift cylinders are leaking internally.

 

[BravoXray]

Depending on how the valve is ported, if the piston seals are leaking, oil is going to be forced out of the rod end as it drifts down. That is because as the ram forces the piston into the cylinder, the volume displaced from behind the piston is greater than the increase in the volume in the rod end of the cylinder. I believe most valves have the rod end port connected to the tank line as it would when lowering the FEL.
If you disconnect the rod end line(s) so they are essentially plugged, the FEL will only drift down a small amount until the pressure in the cylinder equalizes on both sides of the piston, and will be rather high.

 

[Tx Jim]

One or both the cylinders are leaking past the piston seals. Very rare to have a control valve leak internally.

Please explain if what you state is true about faulty boom piston seals which would be similar to the following example?

If you have a ""glass full of water or oil"' & you insert broom stick(cylinder rod) in the full glass of liquid. Broom stick(rod) will cause liquid to exit glass spilling on outside of glass! Concerning your statement where does this oil go if not by internal leaking control valve spool/valve body or visible leak???????
Jim

 

[oldnslo]

Depending on how the valve is ported, if the piston seals are leaking, oil is going to be forced out of the rod end as it drifts down. That is because as the ram forces the piston into the cylinder, the volume displaced from behind the piston is greater than the increase in the volume in the rod end of the cylinder. I believe most valves have the rod end port connected to the tank line as it would when lowering the FEL.
If you disconnect the rod end line(s) so they are essentially plugged, the FEL will only drift down a small amount until the pressure in the cylinder equalizes on both sides of the piston, and will be rather high.

If the statement in bold is true how could you lift the front of the tractor off the ground with the loader and have it stay that way with the valve in neutral position?

Yes they make valves with one or both work ports vented to tank in neutral condition but typically not loader valves for the reason stated above. You want the loader to stay in position.