working on a Dresser 515C. Steers reasonably well to right, hard and slow to left. Need to be moving to steer to left with load. Have 3000+ psi to steer cylinder for the right turn and 1000 psi for the left steer. Any suggestions would be great Thanks
Just thinking here, ram seals or have you ruled that out? CPS
I believe that machine has the rotary valve pilot feeding a steering valve block. There are spools in that block that have to shift and it sounds like you got a sticky one. You can follow the hoses from the bottom of the steering column to the control valve to see where it is mounted. Good Luck!
This has a spool valve with 2 circuit reliefs. The book says that the problem should be with the circuit reliefs. Swapped them and no different. Have eliminated the steering cylinders. They are just a one way cylinder more or less and shows no excessive leakage past packings
That sounds like the old system then that has what looks a truck steering box at the bottom of the steering column and then a rod going back to the steering box on the back half of the machine. If this is the case then have someone inside the machine turn the wheel and see if the rod is moving the spool all the way. Stay out of the middle of the machine though when doing this. I wouldn't want to hear that someone got crushed. Good Luck!
sounds like the orbital valve is binding....
Your left hand steering relief pressure is too low, either you have some contamination blocking the jet bore eliminating the balance pressure on the main poppet, the main o-rings are leaking, the relief is loose in the housing and not seated properly, causing incorret sealing, could be that its just set too low or you have some sort of internal or external leakage (bypassing cylinder, check both with a temp gun after machine is up to operating temp and steering both ways a good few times) which is not common to both directions which isnt allowing the maximum steering pressure on the left side to be built up. Adjust the left hand steering relief valve to spec first, if possible.
Thanks for the help I eliminated the cylinders by checking pressure at the cylinder. Swaped right and left relief valves with no change. Checked the relief pressure with portapower and relief is above spec. Thinkn its something in the valve, possible poppets in the spool?
Don't take this the wrong way, I'm just trying to clear a few things up, to try and help you I'm a little confused as to how you "eliminated the cylinders by checking the pressure at the cylinder" when previously you said you "Have 3000+ psi to steer cylinder for the right turn and 1000 psi for the left steer" Can you please explain the method of which you used? As I previously said, to check for a bypassing cylinder you can either use an infrared thermometer to take a temperature comparison between the two steer cylinders (once the hydraulic oil has reached operating temperature, and you have worked the steering functions, both left and right equally for a generous amount of time) the bypassing cylinder will stick out like a sore thumb. A more accurate way would be to do a cylinder bypass test, to do this, dead end the cylinder, disconnect the return side hose and stall the cylinder, if it's bypassing you would expect to see a flow of oil (depending on how bad its bypassing will determine how much oil will flow). The fact you swapped the left and right steering relief valves with no change (assuming you re-checked the pressures at stall and were the same as previously) leads me to believe there is some sort of internal leakage, whether it be a bypassing cylinder, ACV (anti-cavitation/safety suction valve) stuck open, defective actuation of spool, defective pilot valve (PPC valve, orbital valve etc) It should be noted (not sure of your method, but regardless) that it is not a recommended practice to test a relief opening pressure (or bench setting of a relief) using a portapower due to the inaccurate pressure reading you will get. This is all down to the flow characteristics, and I have seen it proven with my own eyes, when you go to put it in the machine, you will need to adjust it to the required spec as it will be considerably different. So on that note, only check the relief pressures by stalling it out preferably by installing the lock bar if your loader has one. I dont have any experience with your particular type of loader, so I can't be machine specific, only a general understanding of how most loaders work, if you had a WA1200, I could be alot more helpfull
Chris, The steering cylinders on this are just one way cylinders the pressure line from the valve goes to the head end of each cylinder and the rod ends are hooked together running to return. When I eliminated them I stuck a pressure gauge in the line to the cylinders deadheading the line. That is where I came up with those pressure readings. Also as per the book, with the lock bar in place, took the return hose off of the steering cylinders and operated. There was very little oil out the end of the cylinders. The checking of the circuit relief valves with a portapower was how the book said to check them. My thinkn was if it was one of them, it should have been hard to steer in the other direction when I switched them. Also one of them should not have held more than the 1000 psi when tested. When I first looked at this, they had been using it for a few hours loading the feed truck. there was no noticeable hot spots , but I think I only felt the cylinders. The only thing that I can sort out is that if the circuit reliefs are good, and the cylinders are good, I am losing pressure at the spool or the poppets in the spool(which the plugs are all rusted in, so will probably ruin if I did get them out.) To me if I have 1000 psi one direction and 3000 psi in the other it has to be in the valve, but would sure like to see the problem before I order the $2500 valve and have to explain why that didn't fix it. There are just not that many parts in the system. pulled the steering valve out and pressured the reliefs, if they were my problem I shouldn't get over 1000 psi on one of them. Trying to decide if I should put the valve back in and check some more stuff or order the valve and hope for the best. Thanks a lot for all the help, feel like I'm overlooking something.
I dont suppose you (or anyone viewing this thread) have access to an electronic copy of the hydraulic schematics?
By your description you do have the power amplifier steering and not the old manual rod system. I have run into this in the past on a larger machine. The problem then was in the steering valve itself. There was the main spool and a couple fo poppets or other spools. I only diagnosed the valve problem and the customer pulled the valve and brought it to our shop where is was gone through. I know the steering worked fine after that but I'm not sure of what they found when they got the valve apart.
I'll see if I can get it copied from the book - fold out page dont know if I can scan it