Hydraulics Newbie - repair or replace cylinders

[sporteus]

So, I may have to start thinking about hydraulics sooner than later on my auction purchased JD650. Moved some wood for my neighbor last night and when I parked it with the loader bucket in the up position, I noticed that the bucket fell in about 10-15 minutes time (just the bucket, not the loader frame itself). So, guessing the bucket cylinders are leaky since the other hydraulics don't fail in this manner (backhoe boom will drop a few inches over time, but nothing dramatic)

So, first question is how concerned should I be about this? It seemed to hold the loads I was hauling without major incident or slippage, so is this something I just deal with or am I at risk for a major failure when under load? Since I'm just using this around the house, its not like my livelihood depends on it, but I don't want a major safety issue looming either. (Also don't want to invest more in the tractor than I paid for it, that would defeat the purpose)

And assuming I have to address this at some point, do I repair the cylinders or just look to replace them outright? If the cost is about the same, then replacing makes sense to me and is something I can likely do myself. I have no experience having hydraulics worked on, so I don't really know what it costs. I'm also concerned that these maybe oddball sized cylinders that you can't get parts for anymore since the tractor is 30+ years old and from what I can tell those are likely the originals.

Advice is appreciated.

Thank you.
Steve

 

[bumperm]

Steve,

Was the bucket loaded or empty? If it's slowly leaking down with a load I wouldn't worry about it - just put the bucked down when you park if dumping the load is an issue.

Could be the cylinder piston seal, but perhaps more likely the joy stick spool valve. If there are quick connects on the loader, you could undo them and see if it still leaks down - that would tell you.

 

[davesl708]

As bumperm states.

Definitely look at a rebuild before replacing. $ difference is pretty high. DIY is not difficult.

 

[seth350]

I would check for any leaks first and then check your valves. Even if the piston seal is gone from the cylinder, it would not drift all the way down as long as there is not an external leak somewhere else to tank or atmosphere. There is some leakage with the spool type valves, but normally not enough to cause a cylinder to quickly leak down.

 

[bumperm]

Agree.

Last time I bought a cylinder seal kit it was something like $20 or so.

Consider that a cylinder has more volume (hydraulic fluid) on the cylinder side of it's piston than on the rod side (due to the volume taken up by the rod itself), unless there is a path for either the excess fluid to exit the cylinder, or for fluid or air to enter the cylinder, the piston cannot move even if it's actual seal is leaky - in other words, for it to move there has to be fluid movement to or from the cylinder. Usually there is enough leakage in the spool valve to allow leak down to happen, as most spool valves rely on a tightly fitting "rod" type valve that slides up and down in the valve housing to open and close the ports - but with no rubber seals between the ports, just the tight fit of the rod. So some leakage would be expected and is considered acceptable in most applications. Does this make sense? :c)

Th

 

[seth350]

And a piston seal/ring would only show signs of failure by slow movement or no ability to move a load. The cylinder itself would be hot or considerably hotter than the rest of the components. :thumbsup:

 

[sporteus]

Y’all are going to make an expert out of me yet! Thank you

So, I just went out and double checked. There are no obvious signs of fluid leaking from the controls forward (or anywhere else except for a weepy cylinder on the backhoe boom that is irritating me). I snugged up a couple fittings a bit, but otherwise they were all snug. I put the bucket back up and watched it drift south. Noticed that it’s the right hand side cylinder (2nd on the circuit) that is drifting and eventually dragging the left side with it. I checked all the other cylinders for any signs of movement and there wasn’t any observable movement.

So, given this observation I’m guessing I need to focus on the right hand cylinder on the bucket and connections to it because it’s not likely something at the control valve or I would expect to see both of them drifting more or less evenly.

Am I on the right track?

And I’m probably not going to worry about it until next year based on what I’m learning. It holds a load and as long as I’m aware of it and don’t try to hold something in the bucket for extended periods of time, it sounds like I should be OK.

 

[seth350]

If its dragging the left side with it and the left side is not holding the bucket up, then yes it could still be in the control valve.
If its moving, the oil must be going somewhere. Ask yourself, "Where could the oil be going?"

There are two cylinders in parallel, a control valve, and hydraulic hoses all that leads to the tank or the pump.

One sure fire way, if you can, is to swap the control valves for the bucket and loader arms. Should be the same valve for both.

 

[PHPaul]

The bucket curl cylinders on the JD loader for that tractor are cross-connected. In other words, with the bucket off and the SCV in "neutral", you can push in on one cylinder and the other will extend. I did just that to line the pins up every time I took the bucket off or put it back on.

So what I'm saying is, the fact that one cylinder won't hold the bucket in place doesn't necessarily point to the SCV.

I'd kit the right cylinder first to see what happens.

And last time I bought a kit for the 67 loader on my ol' 750 they were a whole lot closer to $50 than $20. That was a couple of years ago, not too long before I traded tractors.

 

[newbury]

+1 for rebuild.
My hydraulics level may be below yours.

My M4700 developed a slow leak http://www.tractorbynet.com/forums/hydraulics/340994-advice-removing-fel-cylinder-please.html?highlight=.

Removing the cylinder was simple.

BUT

My M4700 had a leaking FEL cylinder so I took it off. http://www.tractorbynet.com/forums/hydraulics/340994-advice-removing-fel-cylinder-please.html?highlight=#post4188377

I was advised to get plugs and caps for the hose ends but I have not got them yet. I capped them with plastic wrap and tape, then got a male-male JIC because I had to move the tractor. I removed the plastic wrap and tape and screwed the hoses to each other, strapped the FEL, raised it and moved the tractor about 40 yards.

Then later my BIL told me he had "blown" a hydraulic pump on a skid steer when he did similar. Is there any cause for worry? Would caps act much differently?

I explained to the guy at the hydraulics shop where I got the fitting what I was going to do and he thought it was ok, but I don't know the level of his knowledge.

So be careful, I could have blown the pump if I had used caps.