I haven't tried on a scoob before, and from what I hear they are a ba$tard, but there should be bleed valves dotted around the system. Usually at the top of the rad, somewhere near the thermostat, and in the region of the pipes that go to the heater matrix. Just get the engine running and warmed up, and crack them off GENTLY.
[PING] An idea has occurred. Your footwells aren't damp are they? Sometimes after a summer of being shut off, the heater matrix can rot out causing airleaks and lost coolant.