A Komatsu PC78 have a swing brake problem while its is keyon or arms-in back to netural on handle. We eliminlated all hydraulic related failure. The brake solenoid was received a release singal from the controller for 5sec. Does any one have the same issues? We sent to the dealer shop they claimed this is normal! They said it was the logic behind the enginners designed the controller! This free swing after key-on and arms-in were not normal in operation, imagine the swing brake release after key-on on a slope? We first suspected the computer error, than we replaced another one! The only difference was the first one was happaned on keyon or bucket out, but this time was key-on or arms-in! please help a desperate poor machanic!
The swing brake automatic control releases the brake whenever a pilot pressure switch is closed indicating you are moving something and paying attention to what the house is doing. On the older machines it will stay released for seven seconds after you let go of the controls and don't move anything. So what you are describing is normal. The cross over reliefs in the swing motor will in most all cases prevent the house from turning without the swing brake anyway. A free swing function wasn't put on Komatsu machines at the factory level at least through the Dash 7 series that I know of so if there is one on a newer machine I would like to know that. The free swing function drops the cross over relief set pressures when the operator lets the handle go to neutral position. The swing brake is released all the time when this system is installed and turned on. The only way you can engage it is to set the swing parking brake. There was a gent in Oregon that used to install the free swing functions on logging machines. Some of the older operators felt they wanted their machine to work like line machines. I got on one of those machines on a side hill and picked up the boom. Almost mangled my service truck so after that I managed to kill that function on every machine I put my hands on. I asked the factory rep about it who said if they want to make a machine unsafe to operate, that was up to them. However anything that might happen because of the tampering with the system would also be on the people who changed the factory design.
Therefore, you mean if my swing motor has a leak or problems that may not hold the house while it is in netural! The swing brake just for safety! the time lap for swing brake is normal? but why it only happened on certain functions, it wont happen after swing or arm lift (only happens after key-on and arm-in), Thanks
Please explain what key on means. Is the engine running when this happens. Are you saying that the house will turn just by moving the stick out?
Sorry, key-on means before start the engine! No the house will be free for few seconds after key-on or arm-in, the moving is caused by the slope or lean, bur it is on level or ground that wont be a matter! Therefore we suspect that may be the swing brake, but as you said that might be the crossover pressure relief. Can you explains more about how this work and if that is the case to hold the house from swing, why we need a swing brake for? Again thank you very much for your replies!
Now I understand a little better what you are talking about. You are correct in that the house should not move at all for any reason with the engine shut down. The only way that could happen is if your pilot accumulator is still good and you have the pilot lock out lever in the cab in the operate position. When you turn the key to on it energizes the electrical system which means the pressure switches will now be live. If there is pilot pressure left in the accumulator and a pressure switch is stuck closed the computer will send current to the swing brake solenoid to release the brake. There should be a pilot manifold block that will have several pressure switches. If you have a book find out which one is for implements and unplug it and see if the problem goes away. If it does then replace the switch and you should be good. If not try and different switch and so on until you find the one causing the problem. Keep in mind all this is coming out of my head as I don't have a book for one these anymore. Let me know what you find. If this doesn't work we can try something else. Good Luck!
Hello Jhon! I need your help how to fix the problem about too much delay of the swing brake of kumatsu pc200... This happen both right and left turning during operations, when I move the joystict to nuetral position the braking action of swing brake is delayed for 5 to 7seconds. Also the current in the swing solenoid is delayed to cut off... Why pilot pressure is remains pressure in line for 5 to 7 second and the pressure switch will not off the same time. What is the cause of this and how to fix it?
That is how it is supposed to work. It is a parking brake and not a service brake. The relief valves in the top of the motor are what stops the house from swinging.
Hi John, I have a problem with swing in komatsu PC210-8k. On swing motor I havent got two relief valves just only one. I have the same problem as friends above. Where can I find a solution? In main valve?
I would guess that the relief valve cartridge is worn. Have you checked the pressure on the swing circuit?
Yes I checked. Pressure is correct. 290bar and when I turn the screw of valve the pressure is changing.
Excavator swinging correct, brake is after 7seconds when I dont touch joysticks. When I unscrew two pressure pipes( from main valve to left and right motor swing) Oil Goes out from motor swing all time. Maybe the swing motor has internal leaks and therefore does not brake properly?
Oil going out those pipes all the time is normal. Can you tee into the pilot lines from the joystick to the main control valve and see if the pressure drops off quickly when you return the stick to neutral?
Pressure drops fast, Oil going not from pipes, Oil going out from swing motor from two holes.