had similar problem with the sedan, ended up being radiator cap... replaced that and have now found that when the radiator shop rewelded the top tank back on, 2 of the welds are a bit thin and are leaking under load (dont ask how i tested this but it did involve driving the car)

a slight mist would come out and the fans would disperse it through the engine bay.

If it still does this after they fix it on monday, its either the bottom hose collapsing or water pump is shot....

should be very similar on sr20det.

My solution to you, sell the 180 and get your $$$ back. then you can drive the mrs coupe for a daily.