So I drained the coolant out of the cobra to do some other work that needed a quick connect disconnected at the heater core, and filled new Ford coolant back in (50/50 premix). But I think it had air in the system or something. Drove it till warm, parked it and checked everything. Seemed OK. Went for another ride and I could smell coolant and see the steam. Gauge quickly went up to 3/4 hot. Parked it right away and has been cooling down. Coolant all over the engine. Somewhere I F'd up. Question: 1 - Does the cap have a pressure spring like the classics? Seems so, at 16 lbs. I found a video of it spewing out at the cap and posted it down in this thread. 2 - What step did I miss? My guess is there is air in the system. I filled things up to the overflow marker. Is there a place on the engine I need to open and fill (to get air out and fill into it)? One of those "learn the hard way days". But car seems OK. Did not have a running issue when over-heating, just saw the steam and gauge was moving up fast. But ran fine. Also I just changed the oil, so I feel better it had some fresh Mobil 1 synth in it.