[mylesdw]

The air comes out from the handbrake lever valve (not the servo) at the back of the cab where the lever bolts on. It's probably the valve, mine did that and I have a new valve to go on but I have not tested it yet. You can get rebuild kits for not too much dough. I think the valves stick when they have not been used for a while and then the air in the system does not blow them open as it should. When mine stuck it felt different when you lowered the lever - like it was not doing anything.