Stabilizer stuck down

[CMV]

Lurked here for a while but now have a specific problem that I couldn't answer by searching.

I have an 83 JD 500C backhoe. It does everything it's supposed to but has lots of minor issues as one would expect on a machine that age. One of the issues is the stabilizer cylinders leak down quickly. Overnight they'll be on the ground but while just operating the machine I'm frequently pulling them back up because they've dropped about 10" or so. Anyway, yesterday I was doing some digging & they worked just fine. Then I was moving some dirt piles and I turned around to put them back up all the way. The right one (left as you're spun around to use the backhoe controls) wouldn't move up. Pull the control & nothing. So naturally, I moved it down & that worked fine. Tinkering around & it kept moving down just fine but not up at all. So I ended up with it almost all the way down lifting the right rear tire off the ground.

I'm assuming the problem is in the valve under the control levers.

How difficult a task is it to remove & replace these? The swing valve is pretty sticky as well so would be a good time to do them all assuming they aren't crazy expensive each. But if there's something else I should check first I want to do that before randomly changing parts that I think *might* be the problem.

When I pull back on the lever to raise the stabilizer nothing happens. I don't hear the engine strain like it's trying to move & can't.

 

[whis]

cylinder could be bypassing on inside

 

[Stimw]

My wild GUESS, a piece of seal broke loose inside the cylinder and is acting like a check valve and won't let the pressure back out. ????
If it is the control valve you could loosen the hose to the cylinder letting pressure off and it will lower the tire.

 

[CMV]

My wild GUESS, a piece of seal broke loose inside the cylinder and is acting like a check valve and won't let the pressure back out. ????
If it is the control valve you could loosen the hose to the cylinder letting pressure off and it will lower the tire.

I know very little about working on hydraulics so here come some dumb questions.

If I loosen up the line coming from the bottom of the valve, is there still a lot of pressure in there? Or with the motor off & it sitting overnight (or longer) is there no pressure in the hyd lines? I expect it to loose hyd oil but will it pour out or shoot out at high pressure?

After opening a line, does anything need bled like car brakes do if you open those lines? Or will it just purge whatever air I let in on its own?

 

[Stimw]

You just want to loosen a fitting, not remove it. If there is pressure it will come out with the fitting just loose.
If the outrigger is stuck down there might be pressure on the hose if the problem is in the valve.
Always be careful with hydraulics, they will squirt fluid everywhere and things will drop if the wrong line is taken apart. Normal working pressure is about 2000 psi.
It helps to have clean buckets and rags handy, you can reuse fluid if it doesn't get dirt in it.

 

[CMV]

I'm going to keep putting the opposite outrigger all the way down daily. That should push the stuck one up a little after a few days. I don't know if putting a cinder block under it will help speed that along or if the weight would just crush the block, but will find out. I want to move it enough to move the machine to a better spot to work on it. As it sits, it's all the way at the back & bottom of my property in tall weeds. Stuff tends to break in the most inconvenient places.

When I went out today on my lunch break, it settled enough to where the rear tire was back on the ground. I don't know of that's an indication of anything that might be the problem, but it seemed to leak down on its own like it normally would. I also grounded everything else - all cylinders closed except stabilizers fully open. The hoe arm & bucket are fully extended & on the ground, front bucket flat on the ground. So if I disconnect something I shouldn't, nothing should move.

I use the machine 90% of the time as a front end loader. Would there be any harm in chaining the stabilizers in the fully 'up' position? Would keep the chrome part of the cylinders out of the weather & I wouldn't have to worry about them letting themselves down as I'm doing other work. I could see forgetting and trying to let them down while chained & maybe that would break something. How do they work on newer machines? I think any backhoe will let its buckets down if left to sit long enough. Do they all drop their stabilizers too? I know they don't drop as fast as mine, but after a few days are they still fully 'up'?

 

[whis]

won't hurt to chain them up

 

[SPYDERLK]

Lurked here for a while but now have a specific problem that I couldn't answer by searching.

I have an 83 JD 500C backhoe. It does everything it's supposed to but has lots of minor issues as one would expect on a machine that age. One of the issues is the stabilizer cylinders leak down quickly. Overnight they'll be on the ground but while just operating the machine I'm frequently pulling them back up because they've dropped about 10" or so. Anyway, yesterday I was doing some digging & they worked just fine. Then I was moving some dirt piles and I turned around to put them back up all the way. The right one (left as you're spun around to use the backhoe controls) wouldn't move up. Pull the control & nothing. So naturally, I moved it down & that worked fine. Tinkering around & it kept moving down just fine but not up at all. So I ended up with it almost all the way down lifting the right rear tire off the ground.

I'm assuming the problem is in the valve under the control levers.

How difficult a task is it to remove & replace these? The swing valve is pretty sticky as well so would be a good time to do them all assuming they aren't crazy expensive each. But if there's something else I should check first I want to do that before randomly changing parts that I think *might* be the problem.

When I pull back on the lever to raise the stabilizer nothing happens. I don't hear the engine strain like it's trying to move & can't.

Check hoses, particularly the retract hose, on that cyl. One of them may have a failing/collapsing inner liner and acting like a check valve. ... Im puzzled at "no engine strain" tho. :confused3:

 

[CMV]

I've filled out several online forms for part quotes but so far only FP Smith has responded. $400+ for a new valve. You wouldn't think something that small would cost so much....

Any ideas of where else to look for parts? When I google the part number for that valve and the swing valve all I get are places to request a quote - nothing that shows inventory in stock and a price. Tried ebay & CL with no luck also. There's got to be some places with used inventory for this sort of stuff.

 

[whis]

before I thru parts at it I would check pressure on all the valves

 

[CMV]

I loosened the hydraulic line at the cylinder and used a cherry picker and the stabilizer lifted right up. Every pump on the jack handle on the cherry picker gave a squirt of hyd fluid out of the connection as it was moving up. Red star on pic shows which connection I loosened. Does that indicate that the valve is definitely the problem or at least rule out some things that could have been the cause for the stabilizer moving down but not up? Once I got it about as high as I could with the cherry picker I took it the rest of the way up with just an 800 lb rated ratchet strap - the kind you'd tied down an ATV or riding mower with. Moved easily enough with just that, so I'd guess that means nothing internally broken in the cylinder bound up preventing it from moving.

I should probably do something with that light just hanging there by its wires too.....

 

[SPYDERLK]

If you had loosened the line at the valve it would have put the blame on the valve. As it is the culprit could still be the extend hose acting as a check valve.

 

[CMV]

So I need to repeat the process. I love wasting time

The hose is newer and looks to be in very good condition. Previous owner had recently replaced most/all the lines from the valves to the cylinders. They probably don't have 50 hrs on them. Doesn't mean it's not faulty though...

Dumb question time: YOu can see the puddle of hyd fluid from what it lost. When I checked the dipstick after I was all done, it was still full and should have been at the lower hash mark after losing a gallon or so. I'm assuming that's because I haven't put that stabilizer back down and once I do it will then read low on the dipstick? Do I have to bleed anything since I let a gallon or so of fluid out of the system at a fitting or will hyd fluid just cycle thru and purge any air on its own?

 

[SPYDERLK]

Yes, I think you will not register the loss until you pump new oil to the cyl to extend. Lets assume the problem will repeat. Now, remove the extend hose at the valve and put the end in a jug. Try to retract the cyl. If it goes up normally it must be some issue within the valve. :confused3:

 

[the old grind]

Check hoses, particularly the retract hose, on that cyl. One of them may have a failing/collapsing inner liner and acting like a check valve. ... Im puzzled at "no engine strain" tho. :confused3:

If you could switch the hoses at the valve, it would point to the cyl/hose ('new' or not) or to the valve itself. Not sure, but the 500C may have closed center hydraulics and if so there should be no noticeable engine strain when a cyl/valve is stuck. tog

 

[CMV]

Let it down today, loosened fitting at the valve, and raised it back up with the engine hoist. Same as yesterday - went back up just fine squirting hyd fluid with each pump of the jack. So does that mean I can reasonably assume the valve is the culprit?

Have them both fully 'up' and chained to each other. Never really noticed before but there is hardly any clearance between the stabilizers and rear tires - maybe 3/4". You can see in pic above when the stabilizers leak down & drop a little the pads rub on the tire. Rear tires are newer - maybe they're slightly oversized? I'm sure that will correct itself over time as the tread wears.

 

[SPYDERLK]

Let it down today, loosened fitting at the valve, and raised it back up with the engine hoist. Same as yesterday - went back up just fine squirting hyd fluid with each pump of the jack. So does that mean I can reasonably assume the valve is the culprit?

Have them both fully 'up' and chained to each other. Never really noticed before but there is hardly any clearance between the stabilizers and rear tires - maybe 3/4". You can see in pic above when the stabilizers leak down & drop a little the pads rub on the tire. Rear tires are newer - maybe they're slightly oversized? I'm sure that will correct itself over time as the tread wears.

Sorry for the misunderstanding. ... I had meant to retract the cyl in the normal way using the hydraulics. -- A slow, therefore near pressureless, compression of the cyl may not cause a faulty hose to act up.
,,, Its possible it will turn out to be the valve, but yould hate to go there before the easy stuf is eliminated as best you can.

 

[whis]

the only thing you are proving is you have oil in the cylinder, put a pressure gauge on the hose or at the valve, or as one guy mentioned swap hoses at the valve and try it