Desperately need help on my 1970 loader. Does anyone know why my brakes are locked up and won't release. It is an air over Hydraulic system. When I last started it,I tapped on the brake pedal a few times because the brakes were locked up. I pushed down really hard once and heard a load exhausting of air and pedal when soft. It did air back up to a normal pedal again, but still locked up. If I disconnect the line to the front air tank to empty it, the push rod retracts and unlocks brakes. They will begin locking up again once air tank refills without the pedal being pushed. Possible stuck treadle valve or perhaps EQR valve for brake cluster?
If I'm reading this right you say the brakes are only staying locked up when you have air pressure in the tank? If that is the case I would suspect the treadle valve is supplying air to the brakes. Two things I can think of right off. First is there is something not allowing the valve to return to the "off" position. Like the plunger under the brake peddle is sticking down. Second would be an internal problem in the valve itself. Also just guessing this being a 1970 machine it has a Bendix E-2 valve, I'm attaching a service bulletin on those.
Caseybow, just noticed you are new here so welcome to the forum! I forget the rules but I know before you can post a picture or upload a file you have to have a few posts maybe three? Good luck with the brake problem!