2004 link belt 160lx excavator S/N K2J16053 4,300hrs Two days ago, machine ran great, good power, all functions worked as they should. By the end of the day I noticed the stick (dipper) function slowed down considerably. I shut the machine down for the evening and returned to job the next morning. Upon start up to warm the machine up, without the hydraulic control lever engaged the stick automatically went out all the way and I could not get it to come back in with the controls. I also noticed bucket function was very slow. I shut the machine down with the boom raised and the stick drifted in to the 90 degree position (straight up and down). Had dealer come out and they were pretty much dumb founded. The road tech snapped an allen wrench off trying to get the pilot pump off. After this he left assuming the pilot pump was bad. Next morning I successfully removed the pilot pump to look at the gears inside and everything looked great. Has anyone ever experienced anything like this? Where should I be looking? I took the valves out of the main valve block for the stick function and everything looked good, no springs or seats broken. All filters and fluid look fine to me.
Did you take the pilot section apart on the stick valve? This is where tiny debris can really cause trouble. It takes some really bad stuff to hang up a hydraulic spool. Just a bit of o ring or the inside of a hose deteriorating can plug up the small openings in the pilot section.
Good day Cylinder seal allowing by-pass will always extend the arm may well be worth checking this out first. Kind regards Uffex
Thank you for the quick response…I did not take the pilot valves out, I took the valves for stick function out of the main valve….they were clean and nothing unusual, I would imagine the pilot valves would be right behind the cab?
Uffex, Thank you for the timely reply. Even with the hydraulic control lever not engaged in the cab? And when the stick goes all the way out I can shut the machine down and it will come down to 90 degrees slowly by itself. I did just have the stick cylinder repacked about 35 hrs ago…I will definitely be looking into having it taken apart. I figured the cylinder bypassing would make it go out like that but what’s confusing is that it will do it as soon as I start the machine and do not even engage the controls.
I would add to uffex's post that it is likely that the packing was damaged when the cylinder and rod were mated back up. I would suggest removing the hydraulic return filter and looking for packing material.
What made them suspect the pilot pump? Seems like a case of lets throw parts at this machine. Symptoms don't even really point to a pilot pressure problem.
This will be the next step after I take a look at the pilot valves for stick in/stick out function. thank you for the response and insight!
Quite honestly I have no idea…it didn’t make sense to me what the tech was saying and doing…I will check filters again, check pilot valve for stick in and out and of nothing else I guess I’ll be taking the stick cylinder back off to have it inspected. Thank you for your response and insight!
Good day Attached may help out. Kind regards Uffex
Good morning UFFEX, would you start looking into the pilot controls with the symptoms I have stated or would you inspect the internals of the stick cylinder first? Any input would be appreciated. Thank You
Good day Mike If you can drag the arm in the out (Cylinder in) position, raise the boom as the arm drift's inwards raise the control lock out barrier (Safety) if the arm stops it means your issue is with the pilot system, if it continues to drift inwards I would be more inclined to suspect the cylinder or debris from the original failure. Come back with the results I will try to help some more. Kind regards Uffex
Uffex, The arm automatically goes out without the safety engaged to unlock the controls and I cannot bring the arm back in with the controls unlocked. The safety lever does not affect the arm cylinder from stopping automatically going out. If I shut the machine down with the boom raised, the arm will drift back into a 90 degree position (straight up and down). That being said, should the valves allow flow to the arm cylinder to make it go out automatically? Thank You
Good day Mike I need to be sure that I am understanding your post exactly please look at the attchment and confirm if I have the correcct pitcure. Kind regards Uffex
UFFEX, this is EXACTLY my issues
Ok Mike first I would suggest a pilot pressure issue would affect more than just the arm, I would suggest a likely cause of the issue is that of debris from the original cylinder failure has lodged the spool in the open position. Fortunately, checking this out is not so difficult while my Link belt information is not as good as I would like I will assemble some information for you. Kind regards Uffex
Thank you sir, I will wait to hear from you!
Hi Mike Please see attached. Kind regards Uffex
Uffex, Will do this tomorrow and report back, thank you as always.
UFFEX, I checked the difference between the Arm spool 1 and Arm spool 2, there is roughly a 5mm difference between the two…I am thinking this is where my issue lies. I would imagine the distances from the edge of the valve blocks should be identical and one is stuck in place allowing free flow to extend the arm automatically. Please let me know what you think. Thank you as always
Hi Mike The spools will only have between 10-12 mm of travel so to me that means the spool is half open. Remove the main lines and see if you can fish the debris out. Kind regards uffex
Uffex, I removed the two lines that come off the boom for the arm cylinder that go to the main valve body. There was nothing in there that I could see or feel with a blunt pick, would next step be to remove the spools and see what is in there?
Hi Mike Be sure the equipment is on the deck preferably over night reduce the risk of residue pressure, vent the tank that small valve on the top, this should reduce some fluid loss. Remove the spool cap & pilot line. If I am correct you will not be able to pull the spring & spool from the housing. If you can ease it up or down use the mini-um of force to prevent damage to the spool block (Expensive). Use a magnet as you ease the spool in the two ports going to the arm cylinder as any lodged material will be in these ports. Use needle nose pliers to grasp and parts to pull the debris out. Note spool block will cost money so be careful. See attached Kind regards Uffex
Uffex, pulled the spools for the arm retract and extend, sure enough there were chips of metal in the retraction spool, cleaned all out. Digging deeper, I pulled the arm cylinder, inside the hydraulic port on the rear of the barrel I could see a large chunk of steel that is large enough that it cannot escape the barrel. I am hoping the inside of the barrel is not damaged (which probably is not the case). After the cylinder is “fixed” again, I plan on doing multiple filter and fluid changes. Thank you for leading me in the right direction.
Good day Wish you luck, damage is only light. Kind regards Uffex
I see you are in CT also where are you taking the cylinder to be rebuilt? A friend of mine had a cylinder rebuilt and shortly after he hound metal in the filter and something defective in the rebuilt cylinder.
Good afternoon, Sorry for the late reply, I took it to Hydra-power in Waterbury…the Cushion bushing in the cylinder actually blew apart and I purchased a used cylinder. I just mounted it today and everything functions as normal, but the stick cylinder (the used replacement) and swing function take forever to activate….I took the spool valve apart again for the stick function and found zero metal in it this time. I am at a loss with this machine, anyone have any ideas?
Good day As I interpret your post, the speed is OK but the two circuits (Arm/swing) are slow (delay) to react to the lever movement ? Kind regards Uffex
Hi Uffex, speed is incredibly slow and function is delayed….machine will not swing left or right but looking at the pump pressure, it is getting signal from the pilot control to swing. Arm in and out raises the pressure in the pump as well, but the arm does not really Move unless I hold the function for a minute or two. I just noticed the machine will swing if I track back and forth. I also noticed, when I took the spools valves out to check them after I installed the new (used) cylinder, there was a massive amount of air bubbles. Tomorrow morning I guess I’ll top off the hydraulic fluid and see what happens. I am at a loss with this machine and don't know which direction to go next with it. I’m sure any advice will help at this point. thank you as always
Good day Mike According to my information you have two main pumps and two main sections of the main valve block. Each pump serves its own section. The side that has an issue is primarily the Arm - Slew - Right track, it also hosts a secondary valve for the boom & option. If this is a pump problem I would expect the right track and option to be problematic, the track would show up by crab crawling, speed is down to flow from the pump. As the machine has suffered a pretty bad injury has the filters been checked / changed as this appears to be an ongoing repetition of problems any debris floating in the hydraulics are likely to be problematic. Kind regards Uffex
Uffex, The filters have been changed and the fluid has been filtered to 5 micron. The right track does not seem to function slowly, it will move in high range as well. I did notice (after installing used arm cylinder) when I took the two arm lines off the side of the control valve block tons of air bubbles came out with the fluid that escaped the valve body. When I removed the arm spools there was no metal in them at all and they came out freely from the valve body. What would be my next steps? Thank you
Could there be stuff plugging up in the rotary valve, I don't know the specifics of your machine but might be worth checking.
Good day Mike The fact the track performs Ok takes the pump from being suspect, still maybe the regulation let me take a closer look at the schematic and come up with some suggestions, I am assuming that the boom is good. The common component to both slew & arm is that of the RCV (lever in the cabin) please check the pilot pressure to the main valve. Kind regards Uffex
Good day Please see attached. Kind regards Uffex
Good day sir, So all was working well on my 160lx, pilot pressure was a little low, so I went to adjust to 565 +/- 15psi as my manual states (it was at 350+/-. Turned the pilot valve in all the way incrementally with no change in pilot pressure whatsoever. Machine functioned at the same speed, which was a little slow but bearable. Changed pilot filter for a new one and now the machine will barely move. The old filter was barely letting fluid by. After I removed it, I poured clean hydraulic fluid in the center of it and it barely came out. I then ran the machine for about 45 minutes to an hour after the pilot filter change with extremely slow function, and now it won’t swing again. Should I check all the screens at the pilot controls again? Any ideas?
Good day If the pilot pressure remains low when adjusted is either the pump or the relief valve. Most probable the small gear wheel pump 350 is too low and may well be the root cause. Kind regards Uffex
Uffex, I also noticed this morning that now the 2 main pumps aren’t making pressure. They max out around 2,200psi now. Would the pilot pump affect the main pumps pressures as well? I don’t understand how changing the pilot filter and trying to adjust the relief valve which is still reading the same as before attempted adjustment (turned all the way out and all the way in) would cause the machine to function like this now with no swing.
Good day Mike The small pump provides the movement of the main spool, low pressure prevents the spool full shifting. You cannot measure main pump pressure unless the small pump is working correctly. Think of it as the lever of old style. Kind regards Uffex
Just on a pure whim here, take a look at your safety lever valve. When you flip the lever in the cab, you activate (close) the pilot system. It is designed to drop (return) all pressure when open. If that is leaking over, your pump cannot provide enough volume to get the higher pressure. A quick check to possibly find a weak pump or bypass is test pilot pressure at idle compared to high idle. That pump is pos displacement so it should perk up. If it does not, I might suspect something in the regulator section, or some other relief. But very odd combo. And I would want that damn hydro cylinder back for analysis. Buffers don't just "blow up" without severe abuse OR was assembled wrong, which is probably more likely.