bucket won't stay up, Gehl 4500 skid steer

[Gravdigr]

I just picked up an older GEHL 4500 skid steer at an auction. Everything seems to work fine. There are no hydraulic leaks but the bucket will not stay tilted up. With a load in it the bucket slowly tilts down. Now I am somewhat familiar with hydraulics. Am I right in thinking this is probably the valve body? Can't they be rebuilt with new rubber rings inside?

Any help would be greatly appreciated.

~Digr

 

[Renze]

Valve body ?

First start to look at the piston seals of the hydraulic cylinder: these are a much more probable cause.

I built an older loader onto my fathers 5245. i have no idea how old this loader is, but i think mid 80's.
Last year i had a badly leaking cylinder, outside as well as inside.
When i opened it, i found O-rings that looked like rats had bitten on them ! They just fell apart due to rubber aging.

It cost me about 25 euro per cylinder. Maybe i payd too much, but i brought the stuff to the hydraulic guys we deal with at work, and he traced the ordering numbers because i couldnt find them anymore on these seals. His time is also payd, but next time i can order from part number.

I'd look at the ram seals first.

 

[Gravdigr]

Thanks for the reply. I should have stated I am pretty sure the cylinder seals look ok. I've had problems with those on my dump trucks before. Usually it will leave a film of hydro fluid on the piston when the cylinder extends right? The cylinders on this loader are very clean. I was actually suprised given it's age. The other thing making me think it may be the valve body is that at full tilt up with an empty bucket, it takes 20-30 seconds and the bucket is at full dump. It goes down quite fast. I'm gonna double check those cylinders though just to make sure as you are right in that being a much easier fix.....I am just never that lucky heh.

 

[kennyd]

You have two choices, either the valve body which may or may not be rebuild-able...most SkidSteers use poppet style valves, so the seat/poppet may be replaceable.

Second is the cylinders, the piston seals can be bypassing fluid from one side of the ram to the other, That has nothing to do with the rod staying clean or not leaking externally, it's a different set of seals. An easy check for internal leakage is to remove one line from the cylinder, and operate the function that pressurizes the other side and see if any oil comes out of the open port on the cylinder.


Oh, and welcome to TNB

 

[Gravdigr]

Yeah you're right. I forgot about the internal seals on the double acting cylinders. Most of my hydraulics work had been on dump trucks with single acting cylinder. On those if you blew and internal seal you know it pretty quick. I'll try your method to check the inner seals on the cylinders.

 

[jinman]

Second is the cylinders, the piston seals can be bypassing fluid from one side of the ram to the other, That has nothing to do with the rod staying clean or not leaking externally, it's a different set of seals. An easy check for internal leakage is to remove one line from the cylinder, and operate the function that pressurizes the other side and see if any oil comes out of the open port on the cylinder.

Just to add to what kennyd said, you will want to do this test with the cylinders either fully extended or fully retracted before looking for leaks. If you are not at one extreme or the other, you will get fluid leaking out of the open fitting as the cylinder goes to its limit. If it is already at the limit, you will see a little fluid when you disconnect the fitting, but you will see much more in a continuous flow when you pressurize the cylinder which has an internal leak.

 

[kennyd]

Just to add to what kennyd said, you will want to do this test with the cylinders either fully extended or fully retracted before looking for leaks. If you are not at one extreme or the other, you will get fluid leaking out of the open fitting as the cylinder goes to its limit. If it is already at the limit, you will see a little fluid when you disconnect the fitting, but you will see much more in a continuous flow when you pressurize the cylinder which has an internal leak.

Thanks for the backup Jim, I should have mentioned that...

 

[Gravdigr]

Well I'm pretty sure it is the internal seals in the tilt cylinders. I ordered a kit for each cylinder, not too bad, only 30 beans each. Couple things...

It looks like there is a large steel bar the piston goes into that runs the length of the loader arm and actuates the bucket. I assume the piston is threaded into that metal bar? Is a rag and a pipe wrench the accepted method to unthread it if that's the case?

It looks like there is a threaded cap on the end of the cylinder where the piston comes out. Again I assume that you unscrew this cap to get the guts out. Can anyone give me a clue what I am going to be looking at in there? I have a mechanical mind and I'd like to think I can figure this out without having to have someone else do the repacking (and dent my wallet). So any pics or more advice would be much appreciated.

 

[kennyd]

I picture is worth a thousand words...

Can you post one? There are a lot of different ways to disassemble cylinders...

 

[Gravdigr]

If it's pics you want, then pics you shall have. If you need to see anything not in the pics let me know.