Loader Drifting Down

[ids]

Hello,

I was wondering if anyone has ever experienced loader arms drifting down at a fast clip?

This just starting happening Sat, on a running tractor, I lift the arms up (bucket attacked), the loader arms just start moving down, probably about the rate of an 1 inch ever few seconds, I can lift them back up with the stick, but when I let the stick go, the arms go back down again...all fluids are fine, and the 3pt hitch is fine as well.

I am thinking I damaged something, on Friday I got stuck in the mud and had to have a tow truck pull me back out, but I can't think of what is damaged

thanks..

 

[wvpolekat]

You have a seal in your cylinder(s) or valve leaking.

Did the tow truck pull you out by the loader?

 

[ids]

Thanks, but no,

It was actually pulled out by the box blade that was attached to the 3pt

 

[leonz]

Your valve spools and spool seals are shot it happens with both the gimballed valves and the two spool blocks.


Its a no win situation as the culprit is the valve body 99 percent of the time

as the valve bodies are not required to be high tolerance valves in this case.



leonz

 

[wdchyd]

Your valve spools and spool seals are shot it happens with both the gimballed valves and the two spool blocks.


Its a no win situation as the culprit is the valve body 99 percent of the time

as the valve bodies are not required to be high tolerance valves in this case.



leonz

Not to be a Killjoy but that is not true.....90+ percent of the time its the seals internally in the cylinder.....yes the valve can be creeping down but this happens over a period of time due to fluid contamination wearing it out....and technically the seals in the spool valve only keep the oil from running out onto the ground (even without seals the load will still hold the load due to the precision surfaces between the spool and the housing)

besides repacking your cylinders the right way is a cheaper than replacing control valves just to find out you were wrong.....better to troubleshoot before repair.....:2cents:

 

[leonz]

I can tell you from 22 year plus of trouble shooting , repairing and rebuilding hydraulics that if the internal oil spool clearances and seals are shot or there is debris in the spool valve blocking it from centering it will bypass.


before you pull the pins and cylinders if you are capable of doing this and have the plugs and caps for the hoses and cylinders-
release any remaining hydraulic pressue to avoid injury from an oil pressure puncture.

Do this- remove the A port hose and examine the end of the hose for any debris or rubber pieces, also look in the valve where the fitting enters the valve and look in the bore to see if any debris is in that side of the spool.

Do the same thing with the B port hose and if there is any debris that will be the issue and it may require cleaning several times if it continues as the spool seals and piston seals will tear as well.

If the valve body has relief cartrige on the pressure side of the valve body it may have debris in the cartridge or the cartridge may be stuck open a little with dirt or a piece of piston packing or ruber from the hose.


The only way you can guarantee it is a cylinder it to take both of them to be test benched or add two two way needle valves to the a and b ports of the valve and if one or both hoist cylinders is bad the boom will sink to equilibrium and then each cylinder and set of hoses has to be checked by simply raising the boom, blocking the boom, disconnecting one cylinder completely from the boom and plugging the fittings and capping the cylinder ports prior to raising the boom with the remaining cylinder to see if it leaks using the process of elimination.







Unfortunately for the owners of loader attachments they are victims of decisions related to dollars and how much will the parts cost and can we sell it at a profit with these parts and the fact that the builders do not wish to install better quaility spool valves, 2 way check valves/position control valves simply from the higher cost standpoint.





Blocking the boom up and removing both cylinders and having them tested on a test bench is faster than blocking the boom up removing and capping and plugging the right hoist cylinder hoses and capping the right cylinder hen removing it and then reaising the boom to see if the left cylinder is bad first and then repeating the procedure on the right cylinder with the process of elimination
checking one cylinder at a time the boom.


I have seen and had to deal with valve bodies that were rebored, new spool, relief cartridges and seals installed and some times thyey would reuse the old spools and they would not hold a pair of hoist cylinders in the elevated position for the simple reason the valves were NEVER EVER designed to be be rebored and respooled as the clearance tolerances are too wide after the passage is bored and no new spool or reground spool will fix that issue.

My former employer was unwilling to reinstall needle valves in the hose circuits to eliminate the problem for the hoist function on this machine( the boom had to be raised and hold its position to change old bits for new ones and it was always drifting downward with because of the tilt cylinder or the hoist cylinder-the tilt cylinder dropped because the oil bypassed in the cylinder due to its single sided packing and the needle valves were removed by someone in a stroke of brilliance( the needle valves were installed by the machine builder to maintain level with the tilt cylinder to do two things- change the carbide bits and create asmooth level floor while undercutting- the weight of the undercutter bar and the cutting action created a situation where the cutter bar would always sink due to the chains rotating and pulling the bar forward and down from the weight of the under cutter bar, bar hanger casting, slip clutch housing, clutch pack, the boom of the undercutter, and the cutter motor which weighed more than a ton.



which was an undercutter used to create a relief slot in the mine face to relief explosive pressure when blasting the mine face

 

[ids]

Thanks for the advice,

It's interesting, I went outside and took off the hoses (2 on bucket and 4 connected to the loader) one at a time, blew some air into them and clean them out, and put them back on, and wow, what an effort, its seems like some of them really need persuasion to go back on.

I am not sure if this was happening before,. but the loader isn't actually drifting down, what seems to be happening is the bucket drift down. I lift the loader up high and bucket curled up, then in about 2 to 3 minutes, the bucket is completely pointed down - almost as if the weight of the bucket it pulling to hard on the two hydraulic bucket cylinders, but the boom cylinders are not moving and seem to function correctly.


Maybe one of the bucket cylinders went bad,

 

[Thomas]

For some strange reason sounds like air involed..hmmm..did you tighten all conections/disconnect..reconnect all lines.

 

[wdchyd]

I can tell you from 22 year plus of trouble shooting , repairing and rebuilding hydraulics that if the internal oil spool clearances and seals are shot or there is debris in the spool valve blocking it from centering it will bypass

Do you still say 99Percent of the time its the valve spool when this happened SAT on a working tractor all of a sudden....Oh how does this effect curl but not lift circuit if they just "Wore Out"....

I still say troubleshooting is cheaper than just "Replacing the control valve"....maybe your 22 yrs of troubleshooting can explain how you are 99% sure of this....:confused2:

 

[brain55]

Do you still say 99Percent of the time its the valve spool when this happened SAT on a working tractor all of a sudden....Oh how does this effect curl but not lift circuit if they just "Wore Out"....

I still say troubleshooting is cheaper than just "Replacing the control valve"....maybe your 22 yrs of troubleshooting can explain how you are 99% sure of this....:confused2:

I'd like to hear this too. In my 23 years as a tractor mechanic I can count on one hand the number of spool or valve issues I've seen. And have long ago lost count of the number of failed packings I have replaced with this type of symptom. I would never start with the valve being the problem.

Brian