Link belt 240lx hydraulic head scratcher

Thought I would run it past some of the sharp fellas that look on this forum. I'll start from the beginning,machine is a 2006 240lx with a Waratah 622b processing head. When machine gets warm that is when it starts acting up. after about an hour of running the stick will start to slow and pull the engine down,especially when pulling in towards you. After pulling the stick in it will continue to drift in slowly until pushing the the stick out again.The mechanic pulled the load hold check valve for the circuit and rebuilt it and swapped it with the load hold valve from the boom circuit, figuring that the problem would move to the boom if the check valve was faulty. Didn't solve or move the problem. Checked the pilot pressure and it was low. Manual calls for 585psi and machine had 280psi. I have ordered a new pilot pump hoping that it will solve the problem. If that doesn't fix it I don't know where to look next. Any ideas appreciated. Thanks in advance.

Ps. I think this machine is similar to the case cx240 and the sumitomo dash 3 series. But I'm not 100% sure.

Stick drifting in, bad joystick, worn spools and cylinder leaking, etc. What is the pilot pressure on the spool end cap?

mikebramel said:

Stick drifting in, bad joystick, worn spools and cylinder leaking, etc. What is the pilot pressure on the spool end cap?

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That's a really good idea to put a gauge at the end of the spool to watch pilot pressure. New pilot pump just came in. I'll see if it makes a difference.

Also check that the the allen cap bolt spring and caps that hold spool center have not come loose.Need to do a negetive control pressure test as this can tell you a lot what is going on.Did your guy pull the check valves on the ram or the valve block and does the dipper creep if left out

jcb jeff said:

Also check that the the allen cap bolt spring and caps that hold spool center have not come loose.Need to do a negetive control pressure test as this can tell you a lot what is going on.Did your guy pull the check valves on the ram or the valve block and does the dipper creep if left out

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Pulled end cap off,everything looks fine. What exactly is a negative control pressure test? Cylinder does not creep if boom and stick are left in the air. It only acts up when you work it hard and temps get warm. Put the new pilot pump on yesterday. Haven't worked it real hard yet ,but will see what happens.

Neg control is the pressure running through the valve across all the spools in the neutral position as soon as you select a service the spool will move and restrict or block of neg control which in turn takes the pressure away from the spool in the hyd pump regulator and allows the spring on the piston to move the swash plate in the hyd pump giving you flow/pressure increase .Not sure on yours but if you can identify these pipes as you will two and connect a t piece in with two gauges and run the machine you will see if you have a spool moving out of turn when hot . I will see if I can find the jcb info which will be a guide of what you are looking for

Does it drift in under hydraulic pressure or is the cylinder moving from a bypass ? Big difference !!! If there is no pilot pressure at the spool cap, and the spool isn`t sticking in the valve body, no broken springs, it would narrow it down to the cylinder.
What does it do when you extend the arm out ? Does it drift down ? If it only drifts in one direction, I doubt your problem is the load hold check valve as it effects both directions if it is leaking. Have you done a by pass test on the cylinder itself ?
JCB Jeff should have the best info as the JCB, Case and Link Belt are all the same basic machine. Have fun !!!!!

jcb jeff said:

Neg control is the pressure running through the valve across all the spools in the neutral position as soon as you select a service the spool will move and restrict or block of neg control which in turn takes the pressure away from the spool in the hyd pump regulator and allows the spring on the piston to move the swash plate in the hyd pump giving you flow/pressure increase .Not sure on yours but if you can identify these pipes as you will two and connect a t piece in with two gauges and run the machine you will see if you have a spool moving out of turn when hot . I will see if I can find the jcb info which will be a guide of what you are looking for

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Is this the same as the negative pressure that comes up on the diagnostic screen with the P1 and P2 pressures? Here is a picture of the valve itself like I said we swapped the load hold check valves on the outside from the boom of the stick and the problem stayed with the stick. I'm positive it's not a cylinder as it polls the motor down when hot when pulling in the stick. It's something to do with the valve. Going to work Monday ,I'll heat it up real good and see if the new pilot pump fixed it. Here is a picture of the valve itself. All writing on it is Japanese

P1 and P2 should be the pressure of booth hydraulic pumps,

Do you have check valves on the ram cylinder ?

not sure with link belt but usually able to go into dash and operate pressure switch's upper and lower structure not sure if you have p1 and p2 pressure switch but normally have boost function pressure switch which you should see mrv and boost pressure.Been thinking we did have a few which had a problem with the seat on the arv on the valve block which JCB supplied a tool for us as a dealer to line up and hit it square with a hammer to re seat it i did not do any myself but remember it and thought of it as a bodge so could be worth a look in the port .The check valves on the ram have given troubles but you say it does not creep so i guess that rules that out.Other thing to do is to put a t piece into the pilot circuit on either side of the dipper spools end caps 3/8 bsp i think at least you will see if when it gets hot you may see a fault which could be hand controller .Check that the hand controller has free play on the top between the poppets and the large washer also have a look under the cab at the protection plates under the cab for damage as the servo hoses run there and possible to have squashed one on the dipper circuit just a thought.

Thank you so much for your help Jeff. Your knowledge of the sumitomo brand is impressive. I've ran a day and a half with the new pilot pump. So far so good. I'm thinking that maybe the stick spool (or dipper as you call it on your side of the pond is lazy or sticky and was the first symtom of low pilot pressure.it has been cold here.hres a picture of the machine out in the woods.

Also,what is the arv on the valve that jcb gave you the tool to reseat. Sound interesting. Could that cause a spool to drag?would you have to pull the spool to look in the port? Sound interesting.

The tool looked like a metal cork you just put in the arv hole and tapped it to reseat the tapper face. The arv is the aux relief valve mounted in the spool block which protects the circuit from over pressure like if the weight of machine is acting on the ram so as you don't bend the ram /blow hoses ect (you will have one rod side and cylinder side of the valve block and they are adjustable )
Also check that the pilot pressure is not to high as this will cause erratic operation and juddering on the hand controllers .
Also that does look a little chilly its just wet here no sign of cold yet.

Well got the machine warm today and the problem is back. Stick in is very slow and laboring the motor. On the schematic there is a hose burst check valve would that be on the cylinder. I think this is the next place to start looking as the stick out function works perfect. Have you ever seen anything go wrong in these Jeff?

Hi
Just when you thought it was all over .
I would say the check valve on the ram is a good starting point as these tend to fail causing a things to heat up or not work as they should ,you also have a pilot line and tank line from memory check these have not got damaged on the boom.

Is that a Waratah head on your machine? Was it plumbed and installed by the dealer or a private mechanic?

You should probably trace some lines down to see where they plumbed into to get oil for the head. There are all kinds of ways it was done for awhile. Some people took both the arm cylinder spools for the head and used the bucket cylinder port for the arm. You don't need two pump flow for the arm when running a processor but some of the functions for head do require two pump flow. The auxiliary spool was many times used to run rotation and then diverted to run the heel rack if you have one.

So maybe your arm problem is on a different spool now.

Thats a good call John C.

If you have a valve mounted on the dipper ram (stick in your case) you will have a flow valve the larger one and the small one is the releif valve .
Be carefull but you can put stick out so its off the ground and weight is acting on the rod side trace the small bore hose tank line or return line should be marked with a T and should from memory go back to a manifold or the return line across the back of the engine panel/spool block area and pull hose off the valve the tank line if oil come from the check valve port this would be a suspect releif valve (remember to bleed air from tank or you could get wet.
to test flow valve you will need to remove main service pipe best way dipper out and on floor blank hose from valve block and leave the pipe from ram open and then lift boom and see if you get oil flow if so suspect flow valve in block on ram .I have taken pic from manual for you on dipper in action.

Also ARV picture

Thanks Jeff. I was wondering about that regeneration system. I think that could suspect as when it acts up the track speed is slow for 2-6 seconds.its really hard to read that manual from the picture. What manual is it? And where can I buy one?