Not sure I understand, so you guys think that the emergency brake lever when disengaged is not disengaging so the override is working. I checked the actuating arm on the e-brake lever that is mentioned above and it appears to be moving freely. The emergency brake seems to work fine when engaged and disengaged, I really wonder like mentioned in this thread if the actuator knob on dash is plumbed backwards. The truck only has 200 mile since overhaul in 2009 and who knows what they did or who worked on it.
Thanks
Imagine if the valve were plumbed backwards. Normally, in the off "out" position, it does not direct air to the spring brakes. In the "in" position, it does. In your case, it's working (overriding) the spring brakes when you press it in. So...it's working.
What people are talking about is the switch (with the little wheel on it) that's engaged and disengaged by your manual parking brake handle. If something is wrong down there, it would do what you're saying.
Try this:
1. Engage the parking brake. (button on dash OUT).
2. try to drive.
Can't drive? ok...
3. Push in override on dash.
Can you drive? yes.
The override is working perfectly. The problem is with your parking brake actuator for the spring brakes. (which the override is "overriding" so you can drive/move)
There lies your problem. Check the TM on how it's supposed to work and find the part that's sticking or non-op.
While it's erring on the side of brake-on, I still wouldn't drive it until it's fixed. If your override failed while driving, you'd be in for an interesting stop.