Arms Fade

[qtband]

I'm looking at a 742 for $5000. The owner says everything works good, except the arms fade. He said it lifts fine but fades off. What could be the issue and how hard is the repair? Would the spool valve be the issue?

 

[Tazza]

I'd suspect the lift arms are leaking internally first, if that's not it, i'd move on to the load checks on the control valve.

 

[qtband]

I'd suspect the lift arms are leaking internally first, if that's not it, i'd move on to the load checks on the control valve.

So you are saying that I should replace the lift arm cylinders first to see if that works?

 

[flyerdan]

So you are saying that I should replace the lift arm cylinders first to see if that works?

A certain amount of leakdown over time is normal, but if it is noticeable or you have to keep correcting to maintain a certain position that is an issue.
Before randomly tearing into things, I'd listen with a mechanics stethoscope at the valve body and on each cylinder body. Since they are plumbed together at each end, one leaking cylinder should only cause one side to droop. The good cylinder should hold pressure, and if the valve body is good it won't allow any fluid flow to match it.
Based on that, I'd suspect the valve body for that circuit is bad. There are component books in the manual thread for both cylinders and the valve body, as well as specific machine books which should be helpful.

 

[Tazza]

A certain amount of leakdown over time is normal, but if it is noticeable or you have to keep correcting to maintain a certain position that is an issue.
Before randomly tearing into things, I'd listen with a mechanics stethoscope at the valve body and on each cylinder body. Since they are plumbed together at each end, one leaking cylinder should only cause one side to droop. The good cylinder should hold pressure, and if the valve body is good it won't allow any fluid flow to match it.
Based on that, I'd suspect the valve body for that circuit is bad. There are component books in the manual thread for both cylinders and the valve body, as well as specific machine books which should be helpful.

Good suggestion to work out if one is indeed leaking.
Cylinders don't need replacing though, they have seals inside that you can change. Almost like installing new piston rings in an engine to make it give a better seal, just not as hard to do Seal kits should be around about $50, depending on where you get them.