It’s like the devil takes over when engaging the lift. I begin to raise the boom and then it just keeps lifting no matter what wiggling of the joystick I do. I thought trash got in the lift valve spool so I cleaned and polished some minor scratches but this seems to be electrical…. I took the small pressure lines off at the lift valve that goes from the joystick to the valve to make sure oil was not going to the lift side of the spool when it malfunctioned and that seems right…. No oil to the valve to actuate it from the joystick when it malfunctions. It’s Like the ride control takes over and hangs wide open. Tried turning off the auto for ride control and maybe that worked a few times it malfunctioned, but now it’s constantly going straight up…. Sad to say it hasn’t had the filters changed in 3 years according to the date on the filter. I’m starting there then refilling with new hydraulic fluid
Post a Serial Number and a follow-up once you have changed the oil & filters. Do you know how to access Diagnostic Codes using the Monitor panel.?
Hello Nige. I do not know how to access the diagnostic codes, so Pls help me do that.. I will definitely post on my results of the service of the filters and hydraulic oil change. Serial number is 093OHJDHC02233
See attached. It might show up something, it might not.
A8 trouble code shows up
Can you post a photo of the panel.?
These are the only A codes I have…. But There are several others though. I suspect these are circuit codes that came up when I unplugged some solenoids…
If those are the only ones prefixed with an "A" then they are all that is active at this time. 81-740-5. Differential lock solenoid, open circuit. 81-491-5. 3rd function extend solenoid, open circuit. 91-492-5. 3rd function retract solenoid, open circuit. I suggest that you should at least check into the last two Codes because that could potentially affect the electro-hydraulic hoist control. I see your machine is equipped with a 3rd valve attachment. I hope you have a multimeter because you'll need one. I'll send you a copy of the electrical schematic.
The third valve open circuit I can scratch of the list as I cut this wire to replace the pig tail then actuated it, so naturally this code would set. These solenoids are pretty fried at the wire receptacle and I could not get the pigtail to come out. I initially thought this was my lift solenoid. Can you point me in the direction of a lift solenoid on this schematic. My eyes are not to strong. I see section 42 but that looks more like the joystick location. The machine now is consistently lifting as soon as the motor starts. It’s strange because it raises normally them hits it’s stride then goes all the way up. When you turn off the key then sometimes it will come straight down at a medium rate. If I actuate the joystick in the down position I can ever so slightly get the lift cylinders to momentarily bump but not take over the downward drop in any way. So when it starts, the lift will go all the way up and never let up. It just keeps applying upward pressure and yiu can hear the pump straining. It’s like it has another circuit taking over. That’s why I was wondering if there was a solenoid somewhere for the lift circuit that could be afoul
You will need to determine if this is an electrical or mechanical problem. I am not familiar with this particular machine but I have dealt with electro-hydraulic controls on others. This sounds like a mechanical problem at the moment. My guess would be that either the boom up operational solenoid has seized in the up position for some reason (possibly electrical).......or the main boom spool has locked to the upside of its stroke. Nige is the Cat expert. Definitely follow his lead!
That's exactly where I was headed. I just wanted to eliminate the possibility that an electronic fault was causing the solenoid to be engaged. Now after reading the SysOp I discovered that the pilot system is 100% hydraulic. My bad, I thought it was more modern. So the first thing to do would be to disconnect and plug the lift pilot line as it comes out of the pilot valve. Can you confirm that the pilot control on your machine looks like the illustration below.
I was thinking about this last night and determined to try and rule out of this system was hydraulic only for the lift and a few practical tests this morning led me to believe with some certainty it was mainly hydraulic. Previously I had removed the lift valve out of the valve body (it’s about 8 inches long) and noticed right away it was difficulty to get it to slide in and out. I noticed some visible wear on the valve and tried to polish it so it would slide better. I used fine Emory cloth and spun the valve on a drill and got the valve looking pretty good. I tried this three times and I could get it to work then the lift would stick. Right now it worked for ten minutes by removing one spring. The goal trying to get that valve in a different spot. After that failed I put the spring back in I took out and put a shim ( a quarter) in one of the cups on the opposite side of the where I took the spring out and it works. Thinking of trying to get that valve in a different spot. I’ve got this valve body assembly on order but ot is $3000. Good heavens Machine has 14000 hours
Based on what you say above it's quite probable that the valve body is scored as well as the spool. The spool should slide in and out with no more than finger pressure. Do you have any way of looking into the bore to check the condition of the tunnel.?
Ordered and installed the new valve and drained the hydraulic system. When separating the valve body from the valve body pack a huge amount of metal shaving came out. Pls see the pictures for details. After assembly the lift boom will stop about halfway up in the raised position and will only go up if you accelerate the motor. Wondering what the next best step is? The shavings and debris came from somewhere. Wondering if the lift cylinders internally are scored and beginning to lock down from a seal leaking, pump failure, etc.
Something’s fcuked big-style that’s for sure. Lift cylinders off next I would’ve thought, but it’s not my money you’re spending with all the repair work.
Thinking a bit more about it you are probably in for some major disassembly work (the tilt & steering circuits in addition to the lift) because all the hoses and valves will have contamination in them. The tank will also be full of particles. Each hose on the machine will probably need the sponge gun and every valve disassembled & cleaned.
Nige, does this machine have a screen that can be cleaned for the hydraulic system and where would it be?
With the quantity of debris in the photos above even a screen or filter will not remove everything or anywhere close to it. There is a suction screen in the hydraulic tank and also screens in the pilot and main control valves. To remove the screen from the tank will need the oil to be drained (see your O&M for procedure) first, but you're going to be draining it anyway so no problem there. The inspection cover on top of the tank will also need to come off so that the tank can be cleaned internally. Please be under no illusions, you have major contamination in that system. Unless it is properly cleaned out you are simply setting yourself up for more failure(s), and hydraulic parts tend to be expensive. The finer debris will now be everywhere that is fed with hydraulic oil. The implement system, steering, brakes, and the hydraulic fan circuit will all be contaminated because the same tank is common to all of them