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When I first got my truck I temporarily capped the front emergency glad hand. It's bad I know, but my parking brakes still worked just fine. Maybe that's because of a leak I had somewhere else, who knows. I fixed the two way check valve causing that leak and uncapped it. The parking brakes require air pressure to RELEASE them. If you have parking brakes with all air drained out of the system then like others said you are getting pressure fed to them somehow. If that is the case then worst case scenario you could start by tracing that air line to see where it is hooked up and see if it is hooked up wrong somewhere. It should be the outer line hooked to the brake cans. This line is where the air comes into the can to push the diaphragm and spring outwards and release the parking brake. The middle line is the pressure line for applying the service brakes, and the innermost line is the vent line.
edit: I'll also add that since it has been a day or two then likely all the air is now drained out of the system. Take the rubber plug off the rear of the brake can (if one is there) and look inside with a flashlight. You can tell if the spring is compressed or not. When you cage the brakes you are essentially doing the same thing as applying air pressure; it pushes the spring outwards to compress it. The cage bolts engage that spring and pull it out mechanically instead of using air pressure.
2nd edit: I had the line assignments wrong above so I corrected it.
edit: I'll also add that since it has been a day or two then likely all the air is now drained out of the system. Take the rubber plug off the rear of the brake can (if one is there) and look inside with a flashlight. You can tell if the spring is compressed or not. When you cage the brakes you are essentially doing the same thing as applying air pressure; it pushes the spring outwards to compress it. The cage bolts engage that spring and pull it out mechanically instead of using air pressure.
2nd edit: I had the line assignments wrong above so I corrected it.
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