I have a 310e backhoe that will set the parking brake by itself. Not at any particular time, simply when it wants to. To get it moving again I have to toggle the park brake switch on and off 1 time (set & release) and it's back to moving again, until it decides to set brakes again. I have checked all fluid levels, and they are fine. I have already replaced the parking brake solenoid on side of transmission, the park brake pressure switch, the park brake switch itself and the 2 park brake diodes. Has anyone else had this issue before? Have I overlooked another sensor somewhere? Any help would be greatly appreciated.
Sounds like you will need to get the meter out and check continuity on the wiring for the park brake circuit. and do a wiggle test. I don't know a lot about your machine but if you post a serial number someone can help you better and possibly confirm what I am saying. If I had to guess your parking brake circuit would go as follows. Fuse to the switch. From the switch to a relay, from the relay to the solenoid. Somewhere in those wires you have a bad connection, loose terminal,or a broken wire. It sounds like you are losing voltage to either the relay or solenoid momentarily. In which causes the park brake to set and the park brake indicator light to illuminate. That is why you are able to turn the switch off and back on to regain a released parking brake. I am betting on a loose connection. Good luck.
You did check the transmission oil with the engine running? Make sure that level is correct. Check the connection of the E02 White wire at the starter solenoid. That wire supplies the ground for the Park Brake latching relay. If the ground is lost, park brake will apply.
If it is electric, simply remove the plug.
Honcho, the brake is spring applied anytime there is not sufficient hydraulic pressure to release it. For example, when the tractor is off, the brake is on.