Hi all, Round one (near total loss of hydraulic power) turned out to be an easy fix of just a clogged strainer thanks to y'alls help, so really hoping I get lucky a second time while I continue trying to sort out this old beast. 1) When I move the stick to swing the cab around, I can hear the motor/pump start working harder (like it does when the boom is moving) but there's not so much as a twitch of movement in either direction. The big swing lock peg is in the unlocked position, but beyond that I'm not sure where to start digging. I'm fairly sure it had swung around ok earlier this previous year at the yard, but I can't quite swear to that. I'm not sure if it has a swing brake or not, sounds like that was optional on this model and I'm not sure what it'd look like if it had it, and the wiring on here is a kludged mess so I can't tell if there was previously a swing brake light/switch on the console or not. Any tips on likely causes to investigate? Also a couple things I've failed to identify while trying to figure out why it wont swing. 2) The first two pictures are from inside the battery bay, metal box with a red light blinking about 2hz, with a toggle switch below it. Flipping the switch doesn't seem to do anything I've been able to identify, but the control board inside that box is surprisingly complex (and shiny clean) for this old machine so seems like it ought to be something important. Anyone know what that is/does? 3) I also just noticed that the bottom of the pump coupling area has a threaded hole with nothing attached, and seemingly nothing in the area designed to attach to it. It's slowly dripping what looks like hydraulic fluid though, so I imagine there's supposed to be "something" here - what am I missing? Big thanks for the help as always.
It’s got a swing brake in the swing motor. Spring apply, hydraulic release. I’d say you have a solenoid or something that’s not telling it to release when you try to swing. If you can locate the solenoid you can run juice straight to it to verify it’s good then work your way back. You can also release it with a porta-power in a pinch. It’s rare they lock up mechanically. Follow the brake hose from the motor, usually smallest hose maybe -6, to the solenoid and work your way through the wiring from that point. It may have a fine swing switch in it, may even have a switch to set the brake. I’m not super sharp on Komatsu. As far as the light and switch I’m not sure. The hole with fluid dribbling out is the cavity between the pumps and the motor. As far as I know it should be dry although a little fluid out of it isn’t uncommon with seals drooling. Hope that helps!
A bad or unpowered solenoid would make sense, and hopefully make this an easy/inexpensive fix. The wiring is a mess, so something breaking or coming loose there would seem very feasible. I'll see if I can try to track it down and get some power to it to test it. Per the manual, assuming it has the swing brake installed, there ought to have been a swing brake toggle switch on the console, but that's long gone, and since there's random wires dangling with no labels, I'm not sure which wire, if any, would have been to that switch. Just how strong would the brake be? Apparently when they loaded this up and trucked it down to me, no one set the swing lock pin, so it seems like dumb luck it made it two hours down the interstate without going horribly wrong somehow. That has me slightly concerned it may be a bigger issue jamming things up, but hopefully just means the brake is good and strong.
Finally located the right area and all the plugs and brake solenoid. Assuming I've got the right plugs (service manual has pictures that mostly match up now that I'm looking at the right area, but in my copy the pictures aren't real clear) none of the continuity or resistance tests passed, so seems I likely have some wire breaks to sort out there. I'm going to check tomorrow if the local komatsu dealer has some of these econoseal plugs so I can run 24v to the solenoid without having to strip existing wires, hopefully that'll at least confirm the solenoid is ok and I just have to trace out wires to repair. I suspect in the end it may be easier to just try to locate a whole new wiring harness, and redo all of them fresh...
There should be a toggle swing somewhere on the right side console in the cab that will release the swing brake. On a machine that old it might be gone or wired around. The computer with the lights blinking control the pump output plus there is a swing brake timer that will release the brake when something is operated and set the brake when nothing is moved for more than seven seconds. Possible problems with a stuck swing function; Wiring issue to the solenoid is the most common cause. Check for voltage on the plug when you move a joy stick. There won't be any voltage unless something is moved. Solenoid coil is shorted through or burned out. This can be checked with an ohmmeter. You can get coils sometimes from hydraulic component supply places that will fit the stud on the valve. The diameter of the stud is the critical spec you need. The timer in the computer can go out. That is why they put a bypass toggle switch in the cab. It will keep the swing brake released all the time. If and when you find the switch, shift it and see if the swing works. If it does then you have a bad computer. I don't think there is any replacement for them anymore. The swing motor can be broken. Check for brass particles in the hydraulic reservoir suction strainer. If you see a lot of brass, you got lots of troubles. Swing reduction gear under the motor can be broken. Check for oil on the dipstick. If none, you have problems. As for the leaking oil on the damper case between the engine and the pump goes, they used to put an eight inch pipe plug just above the bottom of the case. You put oil in the case until it came out of that plug hole and then re-installed the plug. Two things usually happen for your issue. The rear main seal on the engine starts leaking or the input shaft seal on the pump starts leaking and you fill up the damper case and burn out the speed sensor. I've seen them so hot they burned the paint on the outside of the case. You have to pull the pump to fix that or you can get a small pan and put a diaper in it to catch the oil and make sure you monitor your levels. The red flashing light on the computer means that you at least have power to the computer. I'll have to look around to see if I can find my old notes for that computer to be able to tell you what that means. Good Luck and let us know what you find.
Thanks for the rundown john, I tested most of that today. Checked voltage at the plug when trying to swing, 0V Solenoid shows 26 ohms across the two wires coming out of it (I'm assuming that means the coil is fine, though I'm not sure what proper spec is for it). No bypass switch in the cab, and since nothing is labeled in that birds nest I've been unable to figure out which of the dangling wires in it was once for that switch. There're a couple plugs in there disconnected with 2 and 4 terminals, and a few single wires as well. No brass particles in the suction strainer. Dipstick on the swing motor has proper oil level, and oil looks clean. I tried running 24 v to the solenoid directly, fairly sure I heard it click once or twice but it wasn't consistent. I'm thinking maybe a weak spring making it slow to return, but can't say for sure yet. When I disconnect the 3 hydraulic lines on top of it to pull the solenoid out, is oil going to come pouring out, or just a trickle? Unfortunately somewhere along the way the starter seems to have died on me, no clue how that happened, but guess I'm fixing/replacing that before I continue with this swing brake issue...
I believe there is some kind of nut on the back of the solenoid coil that you can remove and then the coil will slide off the stud of the valve without opening up any oil at all. The coil itself is replaceable but not through Komatsu. They want you to purchase the whole valve.
Sorry about the really long delay getting back to this - right after the starter died a bunch of other unrelated stuff came up, but finally got around to replacing the starter (old must have been weak, fires up way snappier now) and taking a look at this again. I removed that hand nut and the coil on the solenoid slid right off, but the shaft it was around seems to be frozen. I cant push it in or pull it out or twist it by hand, tapping on it lightly with a hammer didn't budge it either. Is that visible shaft supposed to move, or is there something internal to it that does instead? I also put a multimeter on the two wires leading into the solenoid, and I'm seeing no voltage across them when trying to swing, so that would seem to point to a potential electrical issue as the cause or in addition to a bad solenoid. The wiring in the arm console for this is a mess though, I've been trying to trace things out looking for a break, but not much luck so far. Looking at the electrical diagram, there's an oil pressure switch "somewhere" that I assume would block the solenoid power if it was low or malfunctioning? The manual also mentions a bypass switch for that sensor, but I've yet to see anything like that on here. Is there some trick to identifying all the various plugs and connectors on here, because I've not seen any labels anywhere in the machine? Troubleshooting this would be a lot easier if I could be positive which plug is which when it says "check resistance on CN18" or the whatever.
The shaft you see is solid and does not move. The spool is inside and does not have a way to manually move it. In your photograph the toggle switch under the circuit board is to bypass the computer. There may be another toggle in the cab depending on your serial number. Early machines had a separate swing brake timer from the computer while later machines incorporated that timer in the computer itself. If the timer was in the computer there was a bypass switch in the cab somewhere. I've seen them behind the key switch before but my memory is a little hazy about it. Did you check the coil for resistance? What were your readings. If the computer is not allowing a connection to the solenoid it won't work anyway. I don't have a book for that machine so don't know what the red light on the computer means. There used to be a decal right on the front of the computer that told you what the lights meant. Yours is long gone. Komatsu put a tag on all the connections which were easy to read when the machine was new. Yours is probably thirty years old so you can't count on finding any tags now. You will likely have to just relate what you see in the diagram to what you find as you explore the machine wiring.
Just checked the coil, 28 ohms resistance
Manual describes the mechanical brake as optional, given I'm not going to be operating on any slope for the foreseeable future (my land is completely flat, only way I'd have a slope is if I start digging, and that's not happening any time soon), seems like I probably dont truly need the mechanical brake. I don't suppose it can just be removed/disabled without tearing the whole swing system apart?
Went back out to study it for bypassing the brake. I ran 24v direct to the solenoid, and got nothing - no audible click, no swing, so clearly it's not doing its job. On top of the solenoid, there are 3 hydraulic hoses, one comes somewhere in the front with a mass of other hoses (the joystick valve I assume?) into the near middle port, one goes from the port closest to the solenoid nut to a port near the top of the swing motor assembly, and the 3rd on the rear side goes past the swing motor and heads towards the back somewhere, guessing thats just flowing back into the tank. That leaves me thinking I could bypass the solenoid and brake on/off functionality completely by connecting those first two hoses together, and in theory, the mechanical brake should just disengage as long as the machine is running?
You need some help from someone that knows a little bit about hydraulics and the machine itself. I've never seen a machine meant for the US that didn't have a swing parking brake. It is pilot operated so you could just find a way to tee into the hose feeding the swing brake to release it. But again, it is pretty obvious that you need someone looking at the machine who can provide the information you need to diagnose what is really going on.
I went and took some photo of a 200 size machine for illustration purposes. I'll load them in and discuss what each photo is.
The computer is in the lower right corner of the valve compartment. The decal in the section photo shows what the lights are doing when the system is working normally. The last photo shows the fault indications. Unfortunately I only had a gray market machine available to me so I believe the descriptions are in Japanese. If anyone can read them I would appreciate knowing what they say. A couple I can figure out.
The next photos will show the swing motor, swing park brake hose and the solenoid stack and wiring.
The last photo shows the wiring going to the solenoid stack. Good Luck!
I bypassed the solenoid this afternoon, and swing worked just fine, so definitely a bad solenoid or power to it issue; really happy I ruled out a bad swing motor as that would have likely sent this to the scrapyard. I'll see about getting that pulled out sometime in the near future, hoping I can take apart the valve and just clean it or some such, looked like a new one would run me 700-900. It swung fine while it was at the yard but it'd sat for awhile after that before I eventually bought it and brought it down here, so could just be stuck from sitting or some crud, fingers crossed. I'm guessing mine is grey market as well, since there are several stickers on windows and the like that are in japanese, for the bits that are left. The Japanese part I can kind of help with. If you install Google Translate on a smart phone, it has a camera option that'll translate what the camera sees for you, live. Alternatively, you can load up these images in a website like https://translate.yandex.com/ocr and it'll give a translation. These are coming up as: blank blinking-green | It's not like that (mistranslation obviously) / Quick Flashing: H Mode L Mode blank green | S Mode ___________ blank blank | nothing detected red green | The Control Box blink-red blank | TVC Valve Solenoid blink-red blink-green | Turn Sensor red blank | potentiometer red-blink green | Cellnoid / Quick flashing: descaler solenoid valve B the translations for japanese never seem to be *quite* ideal, but usually close enough to get the general idea, and sometimes it shows multiple possible translations. More head on would probably give better results than angled too. Based on your chart, seems there may be something wonky with the TVC valve solenoid on mine since I've got one red blinking light. I suspect a wiring issue is just as or more likely than an actual valve issue though, so I'm going to have to keep tracing and inspecting wires I guess.
How did you bypass the solenoid? Do you mean you hooked up pilot pressure to the swing brake from somewhere else? Most likely you just don't have power or ground to the coil. The coil can be replaced without touching the pilot valve itself. Two blank lights on the computer mean no power to the computer. Steady red/green I'm not sure of but possibly the signal that the computer is bad. The blinking red means the coil mounted on the pump or the wiring to it is bad. Blinking read and blinking green I don't know what they mean unless it's the speed sensor. Red blank green I can't even guess what they mean and the last combo should be for the decal solenoid valve control. Your machine should have a manual throttle linkage with a big spring mechanism the pulls the throttle back to mid idle when the machine is doing nothing. Probably the best I can do for now. You might try shifting the toggle switch under the computer and see if it changes the read blinking light. That's to bypass the computer. Does your machine have a barrel switch below the monitor panel that shows H, S, L or is it just S, L?
Bypassed by removing the two hoses the solenoid valve allows flow between when activated, and just coupled them directly together, functionally same as if the solenoid was locked always open. Since manually applying 24v directly to the coil had no effect on the solenoid, and the coil had a reasonable resistance value, I'm currently assuming the valve itself is stuck in some manner. I've tried flipping that switch by the computer a few times, no difference I've been able to notice in either position. HSL on the barrel switch, doesn't have any effect currently that I can hear/tell. Manual throttle linkage needs reconnected, its gone and been replaced with a broomstick wired to it in the engine bay (I swear every old excavator around here has the same hack...) I'm going to see if I can get that connected back up in the near future, I think I've got a control cable around here somewhere that will work for the throttle linkage. This old beast will handle the stumps I need to rip out at this point I expect, but its definitely had someone do a bit too much hacking with it over the years.
I am currently dealing with this same issue on a PC 128 it's in about the same condition as this one described maybe worse, wires are hanging everywhere , disconnected , tied together , computer is out of service , trying to locate the swing brake solenoid today , this post was very informative ,thanks a bunch
Same issue komatsu 200 lc-8 swung fine when parked 2 days later go and it wont swing. Where is swing brake solenoid