Hi all, just set up an account but have been reading threads for a while now. I have an ex60-3 that operates perfectly cold but when it warms up the pressure to the boom down function drops down to about 20 bar All other cylinders still build 260 bar when warm including the boom up function so it's not the pump. I have dead headed the pressure gauge on the boom cylinder and get the 20 bar there also so it's not the seals in the ram. I am getting full pilot pressure to the pilot spool for boom down in the valve chest so there's no issue with the pilot piping. I have also tried changing the overload relief valve for the boom function but made no difference. So I have come to the conclusion that something must be a miss inside the valve chest. Has anyone any experience with the workings of these valve chests or have any drawings for the inner workings? The auto idle doesn't work on the machine as the port that is suppose to sense pilot pressure when the joysticks are operated seams to always get a small amount of pressure at all times when the machine is running. Don't know if this could be linked to the issue with boom down? The auto idle switch works on the travel side. I tried swapping the main relief for travel with the main relief for other functions but this made no difference to the small pressure reading at the auto idle port for the joysticks. Thanks in Advance for help
Good day Compliments on your checks, from your test's the pressure holds up when you check in the opposite direction then I would suspect some port leakage at the main valve, from your text is seems that the boom raise pressure holds up, it may be worth while checking the spring and guide on the main spool. Some machines have two boom spools not sure about yours as our server is out of action. Attached information may be of help Kind regards Uffex
Some issue with attachments try again
Hi, yep system pressure holds up when lifting the boom up. Thanks for those attachments I will be able to use the verniers to measure the spool stroke as this is easily accessible when operating the boom down function. Since the machine operates fine when cold I will take a measurement of spool stroke when cold and when warm to see if the spool is not fully opening when the machine warms. I have had the spool out and it looked but as your attachment states it could be worn in the valve block/Housing. The pilot piping for the boom only seams to go to one spool. So I think that it's one spool operating this function. I can see that the dipper/stick cylinder seams to work off 2 spools. If it's a case that the complete valve chest on the machine needs replacing I may try using a 4 port directional control valve so the I can use the lift line to lift and lower the boom. This would be much cheaper than buying a complete valve chest
Good day Im not sure how you may handle that proposal, temperature effects a number of aspects the fluid will become thinner and components expand and contract at differing rates. No doubt it is internal leakage that is at the root of the issue following the tube back from the trouble side the spool has two sealing surfaces that nearest the opposing port is that of pressure whilst that farthest is that which I suggest you take a close look, it is most probable that this is where the fluid is passing to the tank. (These sealing surfaces are in most circles referred to as lands) We can only suggest replacement of the valve unit I believe you can get competitive replacements from Korea and China if we can help you more just drop us a line. Kind regards & keep smiling Uffex