Hello everyone. This is my first post here and I need a little help. I am a farmer by trade, so my knowledge and terminology of construction equipment is lacking so bear with me. I purchased a CAT E70B excavator which has been sitting for about a year in a field. I repaired all of the electric wires from where the rats had chewed them up and got it running. My problem is the swing function works with the joystick, but when you release the joystick the house continues to turn until it stops due to friction. In other words it freewheels a bit. In fact if the bucket is not on the ground, you can push the bucket with your hand and swing the house. Can you tell me where the problem is, or where I need to start troubleshooting this problem? One more thing: When I depress the house lock rocker switch, the house locks as it should. Thanks for your help.
I assume you can push the house in either direction with the stick extended? This sounds a bit excessive but you might be in Soft Swing a feature that lets the swing coast to a stop. look for a switch for that. It usually is a solinoid controling a valve to let swing oil cross the motor ports. Is it soft in both directions? I had a similar experiance on a 65 ton machine that was fire damaged and hauled in dead. They had backed off the swing line relief valves to turn it to load. Later Bob
Yes, It swings freely in both directions. That sounds exactly like whats going on. I haven't ever heard of a soft swing feature. What Icon would this switch have on it? Or where is it located?
Look for a switch with an arc shaped arrow with head on both ends and an orifice symbol. There should also be a swing brake inside the swing motor that will lock it up with the engine off. To check that extend stick out and bucket off the ground so you can push. Shut off engine and see if the brake is holding. Later Bob
Thanks Bob. The brake is holding as you described. I can't find the soft swing switch. Have any other ideas?
At times the switch will be a top view of the excavator with the arc arrows described above. If you can't find the switch, perhaps the solenoid that releases the brake is shorted to power? Freeing the brake while the machine is running.
If the brake is holding the problem is a hyd leak or easy crossover. How does it respond if you try to swing back the other way to slow it down? Right now we have possilities of soft swing valve stuck on, port relief valves backed off or stuck open and the worst thing but unlikely the swing motor failure. Later Bob
The only switch I can find is the swing brake switch which seems to operate correctly. When I depress this switch, the house swing locks as I assume it should. With it depressed, I can move the joystick and hear the hydraulics loading up, which is what it should do? Correct me if I am wrong. Also, when you turn the keyswitch off, the swing locks up. With the swing unlocked, I can swing it to the left then immediately move the joystick to the right, and you can feel the hydraulics change directions and slow the swing and start swinging other direction. I did notice that in doing this the swing motor tries to lock up, or gets "jerky" in the transition from one direction to another. There was on instant where it locked up and wouldn't release until I let off of the joystick.
There should be a case drain filter to capture any metal that comes out of a pump or motor if it fails. Look for a light line coming out of the swing motor and going to a filter. Change that filter and cut the old one open. I think you will find it full of brass. Later Bob