Sluggish Cylinder

[Don in LA]

My son and I have a Harbor Freight towable backhoe which we mounted on a homemade barge which we use as a dredge. We use it to clean out boat slips. The system works pretty well.

The last time we used the dredge, when my son was operating, when the arm was fully extended, the bucket would barely move. When the arm was retracted a little the bucket would seem to move normally. The other cylinders worked normally. We looked at the arm assembly and there appeared to be no binding or hydraulic leaks. The hydraulic resevoir was at normal level. I'm guessing, but I think we probably have about 150-200 hours on the backhoe/dredge. There is a screw-on hydraulic filter for the hydraulic system which has never been changed. Could it be moisture building up in the system? Any ideas on where we should start troubleshooting?

Thanks,

Don

 

[Transit]

First I would switch the lines from the suspected cylinder to another cylinder to see where the problem goes.
Is the oil clear or milky? If the oil needs changing also replace the filter.

 

[J_J]

Install a hyd gage so you can monitor pressures, and do some trouble shooting. The pressure available, and how much can tell you a lot.

Check fluid as to level quality, and for air. You could swap cyl as Transit said, Disconnect the problem cyl connection at the rod end and extend and retract the cyl to check for any problems.

The bucket cyl could have sucked in some water past the seals. If the fluid is milky, that means there is water in the system, and it has been emulsified, and is no good. If left for extended periods of time, new compounds will develop and degrade your parts and functional capability.

 

[Don in LA]

Thanks Transit and JJ. We will troubleshoot with your recommendations.

If we disconnect the hydro lines and/or change the filter do we need to bleed the system of air? If so, how do we do that?

 

[Transit]

Thanks Transit and JJ. We will troubleshoot with your recommendations.

If we disconnect the hydro lines and/or change the filter do we need to bleed the system of air? If so, how do we do that?

Yes, easily done. Cycle all the cylinders a few times and the air will work itself out.

 

[wdchyd]

Don,

I don't know what control valve you have, but something to check is make sure each valve spool is centered when not inuse....look closely at the spools when centered cuz if a spool is partially off center it may effect a valve section downstream in the flow department......

If a spool doesn't seem to be centered you could have a problem with either a joystick linkage or the centering spring/spacers/bolt in the back cover inline with the corresponding spool could be loose.....

Just something to check.......

 

[wdchyd]

Also Don, these tow-able BH's can be prone to bending the dipper arm cyl hyd rod.....

You may want to disconnect the hoses on that circuit to rule-out a bent hyd rod (straight edge along side would do it also)

 

[Don in LA]

WDCHYD: Thanks for your reply. I'm new to the hydraulic cylinder realm. What do you mean by spool/centered spool?

Thanks,

Don

 

[J_J]

If the spool is not centered, you will have cylinder creep. Most hyd spool valves are spring centered to neutral. No movement.

 

[wdchyd]

Don,

The control levers are connected to the spools (the part that moves in and out) on the control valve......

JJ,

what I'm talking about is when a screw or stud on the backside of the spool comes loose and it looses its ability to self center......maybe I'm describing this condition wrong but when a spool doesn't self center (partially off center) it can slightly block the port so that the next spool inline may be starved for oil (slow movement on cyl)......which is what Don has mentioned is his initial problem on one circuit......

This may be completely off base but I've seen this before on other equipment and it's not too hard to spot without taking the doggone thing apart....

The original complaint was slow movement, and there appeared to be no binding or hyd leaks.......moving the arm a little helped the bucket cyl..??.....without physically seeing this unit it would seem to be either a control valve problem, pinched hyd hose or structural binding (bent mechanically)....Yes/No..??