Yes, instead of desperately pumping rubber hoses, you start the engine and let the air bleed out. Turn it clockwise to silence it or possibly ant-clockwise until it stops hissing and water starts to run out then close it.
That makes sense. So, if it's venting I guess there's too much air in the system and that is what's gurgling? I shall go and unscrew it and top the bambino up.
Okay, maybe not. Didn't actually even twist it and the knurled bit broke off in my hand. I suppose now it's not sealed and will either piss coolant everywhere, or suck air in all the time.
Ho hum, off to the Fiat garage when I get back from Le Mans then
