so on my 270 dlc with 7900 hours on it im having issues with the swing motor not operating properly. when i try to swing it will sometimes not swing for up to 15 seconds and then it will finally go with a bang. other times it works perfect it stops as it should ,it turns properly, everything is perfect. so i changed the swing brake poppet and spring in the pilot control valve cause i figured maybe it is sticky or something but this didnt work. so then i changed the makeup check valves on the swing motor but again no difference. so then i decided to do a swing motor leakage test. i took the small line that goes from the swing motor to the tank return off and stuck it into a jug and started the excavator. my jug filled up pretty fast so i figured maybe the swing brake piston is leaking . so i disconnected the swing brake released line and capped it all off and tried again . my jug filled up at the same rate like a five gallon jug in probably 25 seconds . so first of all while i believe i did do the test correctly i would like somebody to confirm that. i might also note that i hadnt actuated the swing function yet . and if i did do this correctly whats next? thanks in advance everybody
Good day You need servo pressure to release the brake, have you checked the pressure ? Kind regards Uffex
The best way to check problems with the swing motor that don't involve the swing brake control system is to remove it and tear it down for inspection. You can have it out and apart in less than two hours.
thanks for your reply. i havent checked the pressure but i should have mentioned that everytime it acts up the upper carraige will drift . but maybe i should still check or can i assume that the pressure is fine? please advise
thank you also for your reply i had it apart this winter but before i had it apart it did the same thing just way not as bad or as often. it seems that when i took it apart i made the problem worse lol. im quite certain i put everything back correctly. the way i remember it would be hard to mess up but maybe i did. before it wouldnt actually not turn it would just go really slow for a couple of seconds and then it just returned to normal
should there even be oil flow through that motor with just the engine running no levers being moved?
Sometimes it is a matter of recognition of the condition of internal parts as to being good or bad. Sometimes with hydraulic pistons, seal surfaces and springs, they can look good enough and be absolute junk. It takes an experienced eye and maybe some precision measurement tools to form the go-no go decision on reusable components.
Good day If we can speak the same terms, we may resolve the problem. The swing brake automatically applies by draining the servo pressure through a small orifice (the small assembly mounted at the brake housing). This draining increases the time taken to apply the brake, allowing the slew to come to rest before application. In many respects, we can regard the brake as one would consider the hand brake of an automobile (has nothing to do with stopping the slew motion, only holding). I suspect that your issue is something connected to this component, as the piston is spring applied and pressure to release, not so much to go wrong. To release the brake you need about 550 p.s.i when testing check at low revolutions as high revs. can compensate for circuit leakage. Some machine’s brake is released by a solenoid valve, I suspect that is your case, so please check at the brake. If you have a hydraulic schematic for your machine then please post it will help. Kind regards Uffex
Good day Just noted no with the levers in un-opretive position only tank return pressure do not confuse this with main pressure
thank you for your reply . i dont have a schematic handy to post but im fairly certain that this machine does not have a solenoid valve to release the swing brake. the oil comes directly from the pilot control valve as soon as any lever is moved . i will check the pressure coming to it to make sure the brake is being released. is it safe to assume though if the upperstructure drifts that the brake is releasing ? or does this not really prove anything
please explain this statement sir . thanks
Good day Jh If the swing drifts, most probably the brake has released, the swing motor needs a supply of low pressure to be sure when it operates with closed valve it does not starve damaging the motor. Kind regards Uffex
ok so how does it get this supply. im just tying to understand how the system works and operates
do the makeup check valves not do this
Jh I will make an explanation as I understand the subject is John Deer I will use a Hitachi 330 as I do not have the JD schematic, is that OK? Kind regards Uffex
yes sir . i believe they are the same thing anyway thanks
Ok give me a little time to make it
Good day While I make some specific information please see attached general information, I suggest we take this in steps 1/ is the brake releasing when required - correct pressure with low idle -If we give a separate servo feed and we revolve the superstructure by hand. 2/Is the brake applying when it should - if we disconnect the brake release line and plug can we stall out the slew -- swing motion in both directions. 3/ Mechanical failure just be sure that the swing transmission has no nasty surprise sitting in the drain line. (be back in the morning) Kind regards uffex
so here is what i did . first of all since i was parked on a slope it made number one easier. i boomed up and the upperstructure slowly drifted to the downhil;e side. when i released the lever it kept going for a while till finally it sort of grated to a stop . note this is what it does when it acts up. otherwise it stops within an 1/8 of a turn like the book says it should. number two now when i plug the line and try to swing (still on the slope) the upper carriage stays put no drift at all not even an inch. also the machine idle down since no sensor was reading pressure . number three i have not checked but i hope to tommorrow
there is a valve on the side of the swing motor where the brake release line goes in and there is also a pressure sensor on there. im just curious what this valve does
most of the time to get the swing to cooperate i just have to activate another function
Good day JH Please see attached for your information be aware that this system is very common among hydraulic excavators, many will express that the braking may well be sensitive to fluid temperature and fluid visco. I have checked with a few contacts as I find the "Banging" rather alarming having not experienced this first hand. There maybe a floating obstruction to the small orifice this would prevent brake application however release would remain unaffected. I hope the explanation is of help if I can offer more please present your questions. Kind regards Uffex
so but just to be sure the upper structure shouldnt drift even when the brake releases should it. andalso should i be seeing flow through the swing motor like i did with no functions activated please help im stumped lol and i need this machine thanks in advance
well experienced i am defintely not but i feel like since its my machine as long as i dont change unneceray parts then i can try to fix it . i had the dealer try to fix this and he said it was fixed. so i went to try it and it still didnt work and i was out a couple thousand bucks. the guy doesnt care to help me over the phone which i dont blame him as he doesnt get paid for that . but i feel like i can work it out just like him if i only understood more about the machine and what could possibly cause this problem
Good day JH 1/ With the brake release (With servo pressure against the piston) some drift will occur hence the requirement for a brake. 2/ I'm not sure which lines we are talking, and is that with the motor running or stopped? Kind regards Uffex
thank you very much for your help sir. with the engine running but no function activated i got 5 gallons in about twenty five seconds out of the small line on top of the swing motor as seen in the picture
That is the case drain which interconnects with the brake drain line, with the brake in the applied position part of the servo pressure will drain over to the container. I have made a quick diagram attached which is a better explanation. Take care Uffex
ok so if this was with the brake applied since i also did this with the brake release line capped of with the same results then its safe to assume the swing motor is not good anymore or is this not neccesarly the case. where does this oil come from though forgive me for the many dumb questions lol i know little about this
Ok we know where we are - your explanation means that return pressure is leaking through the motor see attached. My advice would be removing the motor to dismantle and inspect. Would you like instructions Kind regards Uffex
Opps attchment
well ive had it apart and i have a micrometer to measure things i just dont know the measurement on everything and also can the motor case be wore out?
You can remove the refill line also then the fluid must stop, for that fluid to fill the container it must be passing the pistons in the motor.
ok sorry for being dumb but what is the refill line
That's the big guy on top of the motor don't worry, I admire you having a go
ok so if i cap it off and try again i wouldnt damage my motor any. but then i sholdnt get any leakage at all right. where does the oil for that line come from i know its from the control valve but does it automaticly get oil as soon as you start the engine?
No you are correct the machine needs a back pressure to fill voids as they occur in the system normally 3-4 bars. All the fluid going back to tank has to pass a choke, this creates the back pressure.
Important items 6-9-21
Should add you are not slewing the machine, no harm will happen
ok thank you for your help i think ill try the leakage test with the big line off first since its raining anyway and i cant put it in a shop
Ok take care, no doubt catch up at some stage
so i capped off the big line, stuck the small line into my container, started the machine andgot no oil coming out. so i guess this elemenates the control block completly (correct me if im wrong) so now ill bust apart the swing motor and see what i find there
Good day JH I would expect a small cross over to the case drain but from your post it sounds excessive, the two possibilities are the lens plate and piston-cylinder leakage. Good luck Uffex
so just out of curiousity can anything happen to the case where the oil goes through into the motor
Good day Both case and refill pressures are low, I would not expect to see any defect. Kind regards Uffex
so i did find damage in the swing motor. the one friction pad was warped and wore off on the outside edge. one of the plates that go against the friction plate has damaged tabs on it. it seems like the brake maybe had to help stop the swing at some point. the pistons were just outside the good range as near as i could tell but a couple are fairly loose in the slipper. the lens plate is scratched . it apears some filings got loose some where. also the shaft has about 3/16 of a turn play. so im not sure what all to change maybe bearings to?
actually as far as that goes even the case has a scratch sort of wore into it so if that is an issue then im leaning towards popping in a reman motor however not really knowing much about this i would appreciate other opinions thanks in advance
You should find an experienced mechanic to assess the damages. I don't know if you can find a reman for that machine.
this is probably a good idea. my dealer does have reman in stock
Good day JH Reman would I believe be your best option please do not overlook to bleed the motor when you rebuild. Kind rehatds Uffex
so after checking pistons again with a micrometer i find that there is actually no play in them which leaves me very confused . so my question is#1 can the lens plate cause leakage #2 can anything else like crossover relief valves or makeup check valves cause leakage . i know im second guessing myself but somethiing doesnt seem right here and i cant get a hold of anybody to look at this thing.
If the seal plate at the open end of barrel and the brass on the barrel itself have scratches or scores that can be felt with your finger tip rubbing across it means the plate and barrel are junk. If you can see the marks and not feel them, then it is likely that the two surfaces can be lapped smooth and be reused. I don't recall if that swing motor has brass liners on the barrel assembly but any marks in those liners mean the barrel is junk. If there is any play in the slipper feet at the bottom of the pistons, then they are junk. If there are any marks on the swash plate that can be felt, then it is junk. Odd wear patterns on the brake steels and frictions usually point to them being put in wrong or falling out of place when the motor was assembled. Since they only engage when the house is already stopped, they should not show any wear at all. Your best bet is to put it back together and get the exchange unit.
Good day As I understand the situation you have a number of options open to you, take your motor to a repair specialist ask for it to be checked out - Go for the reman motor - repair your own motor with a repair kit . Much depends on how confident you are in taking a step. One point is that we should not overlook how many hours has the machine. Normally one can expect a motor to last about 10.000 hours however some have been subject to reverse stopping on a frequent basis and this can shorten the life considerably. If you make a search for piston motor - pump repair you can find many videos on youtube some give good advice others are a little short of knowledge. Eaton hydraulics also publish trusted repair information. One point for sure you will know your machine pretty well by the time you have it working good.Kind regards Uffex
There are no repair kits for these motors. Parts are all ordered individually. I have never trusted independent repair shops for this kind of work on brand name construction machinery, particularly Komatsu. Hydraulic component life is tied to oil cleanliness and keeping temperatures within manufacturer's specifications. I have multiple machines in my territory in excess of 15,000 hours. You can do what you want but most people opt to keep machines earning revenue so franchised dealership reman units are the normal repair option taken. You can repair it yourself, but then you get to live with the future expenses that may incur.
thanks for the advice. im sending it to the mechanic i always deal with and he will advise me on how to procede
so i got my swing motor back popped it on and its doing the same thing way not as bad but same thing . so i hooked up some guages and found that there is close to 600 psi at the swing brake release line and at the valve spool cap . then i took off the spool cap and found everything in good shape no scratches on the spool or anything. so now im stuck again . could this be a relief valve problem by any chance? could my joystick be acting up? could there be too much slop in the gears that would cause them to catch on each other. any advice is appreciated thanks
fooling around with it a bit it seems like the swing brake works too good like its applying too fast or something
Good day As I interpret your post you have pressure of 600 p.s.i. at both the spool cap and the brake release line, in normal circumstances this should be about zero. As you report this pressure is both at the brake release line and the spool cap would cause the machine to swing under power of its own accord as soon as the control lock out has been activated unless that pressure is sitting at both sides of the spool. I suggest you check the pressure at both swing left and right, a combination of pressure would indicate a fault within the illustrated manifold. Please see matchedKind regards Uffex
sorry sir i should have clarified that that pressure is not there till i move any joystick for the brake line but it goes away as soon as i release it and same thing for the spool cap pressure as soon as i move the handle its there but when i release it it goes away right away i believe this is how it should work but please correct me if im wrong
Yes Sir, that is correct, it is how it should be. Kind regards Uffex
have you check your swing parking brake solenoid? It could be a faulty solenoid (i.e sticking or coil is weak etc) or a pressure switch problem. If I were you would check teh swing parking brake pressure switch and then the solenoid.
So when you operate the swing lever, a pressure switch gets activated in the main control valve. this switch then signals the computer to either switch on or off teh swing parking brake solenoid and the machine swings. Usually the parking brake comes on 2-3seconds after you let go of the lever. commonly on Cat the solenoids get weak over time or the pressure switch doesn't get activated or is stuck on. try and unplug the pressure switch and short the 2 pins on the harness side see if it fixes the problem. if it doesn't, a quick temp fix is to loosen the nut on the back of the swing parking brake solenoid, mark the position or note carefully position of the center threaded bolt and screw it in half a turn at a time and see if that helps fix it. you can screw it in a couple of turns to either give the coil a bit of an assist or open fully to operate teh machine temporarily while you get a new solenoid. Should be costing around a 100 bucks for a good copy
this machine doesnt have a solenoid for the swing brake . i put a new motor on a couple days ago and so far its been working normaly