So I'd been riding around in town doing a few errands when I see the temp gauge is entering the danger zone so I decide to limp it home (~10 minutes away).
The last few stoplights, there was steam coming out of the coolant overflow hose, and the coolant was boiling in the overflow reservoir - wtf?
Could I have caused damage to the engine? Warped head maybe?
I've got manuals so am starting the trouble-shooting, but advice is welcome!
A couple questions:
 the fan was not running (so maybe the motor or the switch is faulty), but with 10 degree temperatures today, is that even relevant?
 because the coolant was boiling (BTW - what temp does it do that?) does that mean there's air in the coolant passages, and I'll need to flush the whole system?