Cylinder weak and slow

[chartersj]

The hydraulic cylinder for the arm on my backhoe is weak and slow when extending it and normal when retracting it. The rest of the cylinders work as they should,,, can anyone point me in the right direction in where to look to correct the problem?

 

[BeezFun]

Check the quick disconnects first, that's cheap and easy. If that doesn't help, try switching the hoses for retract and extend and see if the problem follows the hose or the cylinder.

 

[deereman75]

What make and model of backhoe is this? Different companies have different cylinders.

 

[chartersj]

Check the quick disconnects first, that's cheap and easy. If that doesn't help, try switching the hoses for retract and extend and see if the problem follows the hose or the cylinder.

Ok good idea

 

[chartersj]

What make and model of backhoe is this? Different companies have different cylinders.

It’s a MF50A with factory massey backhoe

 

[BeezFun]

I was thinking about your symptom, it could be that there is rust or crud in the bottom cup of the valve body so the spool can't move all the way in one direction but moves freely in the other. You might be able to tell by comparing the valve lever movement in one direction with the other.

 

[chartersj]

I was thinking about your symptom, it could be that there is rust or crud in the bottom cup of the valve body so the spool can't move all the way in one direction but moves freely in the other. You might be able to tell by comparing the valve lever movement in one direction with the other.

I can confirm the problem follows the hoses. So that would rule out the cylinder. The spool has the same travel as the others. This is the older style with a row of handles so it’s easy to tell. It is more useful this way other then the fact now you have to move it in the opposite direction which is in turn makes it opposite to the bucket curl and makes it even more awkward to use. I did notice on that handle when I pull it all the way toward me it will stick,,, none of the other handles will do that. Not looking for a new machine,, it is a ‘75 but was wondering if that may be a symptom of something internally wrong with that valve

 

[BeezFun]

Ok I'd suspect the valve. I'd drop the bottom cup, it's usually held on with 4 cap screws, you can probably get at it without dismounting the valve. If that's a detente valve all kinds of little bearings and springs may fall out, be ready. If it's full of crap that's probably the problem, but even if it isn't try using the valve with that cup off. If it still doesn't work you may need to take it to hydraulic shop depending on your ambition.

 

[chartersj]

Ok I'd suspect the valve. I'd drop the bottom cup, it's usually held on with 4 cap screws, you can probably get at it without dismounting the valve. If that's a detente valve all kinds of little bearings and springs may fall out, be ready. If it's full of crap that's probably the problem, but even if it isn't try using the valve with that cup off. If it still doesn't work you may need to take it to hydraulic shop depending on your ambition.

Ok perfect I will try that first and see how it goes. Thanks for the help!

 

[BeezFun]

The other thing, since it's so old, if you remove the valve lever and take the top boot off, inspect the condition of the spool where it enters the valve body. If it's built up rust over the years that might be preventing the spool from moving all the way into the body.

 

[chartersj]

Ok I'd suspect the valve. I'd drop the bottom cup, it's usually held on with 4 cap screws, you can probably get at it without dismounting the valve. If that's a detente valve all kinds of little bearings and springs may fall out, be ready. If it's full of crap that's probably the problem, but even if it isn't try using the valve with that cup off. If it still doesn't work you may need to take it to hydraulic shop depending on your ambition.

The other thing, since it's so old, if you remove the valve lever and take the top boot off, inspect the condition of the spool where it enters the valve body. If it's built up rust over the years that might be preventing the spool from moving all the way into the body.

I removed the cup and everything looked new inside. Lever side looks good too. The cab covers the controls so I’m sure that helps. Looks like the spool assembly will have to be taken apart. Not sure I’m up for that task though I will most likely take it to a shop.

 

[BeezFun]

OK, didn't realize valves were in a cab, I thought they'd been outdoors since 1975. Just to be sure what you did to diagnose this, did you switch a different valve to this same cylinder, or did you just reverse the hoses? If you didn't do it, just as a double dog check I would connect this valve to a different cylinder and verify the cylinder has a problem. Also connect a different valve and make sure this cylinder works OK. If you already did that, then yes it probably needs some work internally, or at least I'm out of ideas. It's not hard to pull the spool out, just be gentle and make sure you keep everything really clean. Ask your wife for a clean sheet, they love it when you get hydraulic fluid on them. Once you pull the spool look for any burs or flat spots on the spool that might be causing it to not move all the way in one direction. You can clean the small passages in the valve body and the spool with solvent and compressed air. You can't hurt anything as long as you handle it carefully, it has very tight tolerances so you have to rotate and wiggle it around as you remove or insert it. The orings are probably hard, you can replace them but they only seal low pressure. Or you can just take it to a shop, they can test it on the bench and confirm there's a problem internally before they take it apart.

 

[BeezFun]

I did notice on that handle when I pull it all the way toward me it will stick,,, none of the other handles will do that.

I just noticed this sticking you mentioned. That could be a bur on the spool that's preventing it from moving all the way.