I was giving the engine bay a bit of a tidy up when i noticed this valve type thingy attached to the front of the radiator, it has a grey plastic screw off top with an 'H' on it, underneath looks like some type of valve, I'm taking a guess here that it's for the air conditioning gas? but whats the 'H' stand for and whats the inspection glass for? looking empty btw. Anybody any ideas? Cheers ta Nev