Bucket Un-Curls by Itself

[jdb4whlr28]

I've got a Massey 1528 with a 1520 loader. When the tractor is running (or off for that matter) the bucket un-curls (dropping the load). I realize that it's one of two things: the pistons controlling the curl or the control valve. I was leaning towards the control valve because I would imagine that both pistons would have to be internally leaking in order to see unwanted curling... I don't want to spend money on a new control valve if that's not the issue though. Any thoughts??

 

[CCWKen]

You're right. It could be either or both. The control valves don't have seals. They have a machined clearance with sliding fit. They are designed to lubricate themselves by fluid leaking along the shaft. Wear just increases the clearance to the point of excess leakage. The cylinders operate at the same time. It's not uncommon for both cylinders to have leaking seals. The seals get hard and wear allowing the fluid to bypass.

You could test the cylinders by capping/plugging both ports and see if they drift. They should not. If they do, the seals are bad. The valve can be tested similarly. Place the ends of the open lines into a bucket. Start the tractor. Leave the valve in center. You shouldn't see more than a few drops per second coming from the hoses. If you get any flow or stream, shut down the tractor. The valve is bad.


Added You could have the valve spool plated but you need to know the amount of wear so the plater knows how long to leave it in the plating tank. (So many thousandths per hour.) And, there's no guarantee since the spool and valve can wear unevenly..

 

[Egon]

Might be able to test by uncoupling the quick disconnects on the curl???

 

[CCWKen]

Good point Egon. If it has any.

 

[muddstopper]

Cant cap cyl and check for bad seals, wont work. I used to argue that it would work too, but now I know it wont. What you can do is uncurl the bucket completely, without a load. Remove hose on rod end of cyl and work the control valve as to extend cyl , If oil squirts out the rod end of the cyl. the piston seals are bad. If oil doesnt squirt out the cyl, then valve is bad. You might find a machine shop or plating shop that can repair your valve, but it would probably be cheaper to just buy a new valve.

 

[CCWKen]

It works. The cylinder needs to be under a load though. Your method will always produce a "squirt" since there's oil in the rod side that will get displaced as the piston moves. Each to his own I guess.

 

[jdb4whlr28]

Thanks for all the good info guys! I have the piston rebuild kits somewhere in the garage, if I can find them :duh: I was going to start by rebuilding them to see if that fixes it. Massey wants a ridiculous amount of money for the valve. The tractor is only 6 years old with 350 hours on it. This problem started around the 250 hr mark. So I have a hard time believing its the wear on the valve. I took it apart a few months ago and didn't see any noticeable scoring or wear on the spool.

 

[CCWKen]

I'm on the hunt for cylinders all the time for various projects. I've gotten many out of the salvage yard from scrapped equipment or just throw aways. The first thing I do is move the piston to center, fill both ends with oil then plug the ports. I use the shop press to do a push-pull test. (I have a pull-back ram also.) You can tell right away if a piston seal is bad. Just watch the pressure gauge so the press doesn't go over 2K psi.

You can accomplishing the same test with the cylinder mounted on the tractor with a load in/on the bucket.

 

[muddstopper]

It works. The cylinder needs to be under a load though. Your method will always produce a "squirt" since there's oil in the rod side that will get displaced as the piston moves. Each to his own I guess.

What works? You can take the piston off the rod, re-assemble the cyl, without the piston, fill with bore with oil, cap the ports and the rod wont go in and out. The rod itself takes up volume inside the cyl. If you extend the cyl, oil would have to enter the bore to take up the space the rod occupies. If you retract the cyl, the oil that the rod displaces as it enters the bore would have to leave the bore. Oil dosnt compress and if you cap the cyl ports, you have blocked any oil flow into or out of the bore and the cyl rod will be locked in place. You can not cap the ports on a cyl and check for bad piston seals. You could block the ports to check the rod gland seals, but if the rod gland seals are bad, oil could exit the cyl by leaking around the rod gland, but if the gland is bad,you should already be able to see oil running down the outside of the cyl.

If you use the control valve to extend the cyl to full extention and then remove the rod end hose from cyl, you would probably see a little bit of oil just run out of the cyl, but it wouldnt be under pressure. If you activate the control valve to try and extend the cyl further than full extention, and oil gushes out of the rod end port, that means the piston seals have probably failed and oil (under pressure) is bypassing inside the cyl . Piston seals can fail in one direction and not the other, If oil doesnt gush out the rod end port, reassemble hoses, full retract cyl and test cyl base ports in same manner as you tested rod end ports. If you dont have oil gushing out either port while testing, most likely the valve is bad. If while testing, oil gushes out either port then cyl is bad.

I'm on the hunt for cylinders all the time for various projects. I've gotten many out of the salvage yard from scrapped equipment or just throw aways. The first thing I do is move the piston to center, fill both ends with oil then plug the ports. I use the shop press to do a push-pull test. (I have a pull-back ram also.) You can tell right away if a piston seal is bad. Just watch the pressure gauge so the press doesn't go over 2K psi.

You can accomplishing the same test with the cylinder mounted on the tractor with a load in/on the bucket.

You are going to have to explain this, as i cant see your method working

 

[LD1]

It actually will work on the curl cylinders if drift is the problem.

If it has quick couplers, put the loader on the ground to take pressure off and unhook the curl cylinders. Raise the loader BUT NOT THE CURL. wait and watch for drift. Put the loader back on the ground to relieve pressure to hook hoses back up.

With a capped cylinder, you absolutly cannot compress the cylinder, regardless of the seals. Because the rod tries to displace fluid.

But it dont work that way trying to extend the cylinder. Extending the cylinder if the seals are bad can draw a vacuum. Vacuum acts more like air, IE: compressable or uncompressable. IF the seals are good, you are trying to compress the fluid in the rod side, and it wont compress so it wont move. IF the seals are shot, fluid can bypass to the base end. But since you are creating more space than the oil needs, you create a vacuum

 

[LD1]

I'm on the hunt for cylinders all the time for various projects. I've gotten many out of the salvage yard from scrapped equipment or just throw aways. The first thing I do is move the piston to center, fill both ends with oil then plug the ports. I use the shop press to do a push-pull test. (I have a pull-back ram also.) You can tell right away if a piston seal is bad. Just watch the pressure gauge so the press doesn't go over 2K psi.

You can accomplishing the same test with the cylinder mounted on the tractor with a load in/on the bucket.

IF the cylinder is 100% full, trying to compress it would do nothing at all. Only doing the extension test will tell you if the piston seals are bad.

 

[wdchyd]

Thanks for all the good info guys! I have the piston rebuild kits somewhere in the garage, if I can find them :duh: .

Look and see if the piston seals are just oring and backups, they can be upgraded to a better urethane seal

 

[wdchyd]

I was leaning towards the control valve because I would imagine that both pistons would have to be internally leaking in order to see unwanted curling...

If either cylinder is bypassing internally they will both not hold a load

 

[arlen4720]

It actually will work on the curl cylinders if drift is the problem.

If it has quick couplers, put the loader on the ground to take pressure off and unhook the curl cylinders. Raise the loader BUT NOT THE CURL. wait and watch for drift. Put the loader back on the ground to relieve pressure to hook hoses back up.

With a capped cylinder, you absolutly cannot compress the cylinder, regardless of the seals. Because the rod tries to displace fluid.

But it dont work that way trying to extend the cylinder. Extending the cylinder if the seals are bad can draw a vacuum. Vacuum acts more like air, IE: compressable or uncompressable. IF the seals are good, you are trying to compress the fluid in the rod side, and it wont compress so it wont move. IF the seals are shot, fluid can bypass to the base end. But since you are creating more space than the oil needs, you create a vacuum

I have found that even with healthy rod seals, that they cannot hold a vacuum and easily pull air in to fill the space from the extending rod. That is of course when you have bad piston seals.

 

[muddstopper]

Here is a pretty good utube vid I found that actually talks about trouble shooting valves and cyl. The part about capping cyl and testing seals starts at about the 35min mark, section 7, https://www.youtube.com/watch?v=WEHD-1Hac5E, but there is plenty of good info before that part that I found really helpful.