Its leaking?. Does the pressure go right up to 3 bar or so when the central heating heats up?, if so your expansion vessel needs recharging, a possible DIY job. With zero system pressure pump up the expansion vessel to 12 or 15 psi, depending on your manual. Try searching for expansion vessel on this site or googling.
c
September 2007
Automatic Answer
We may have found other answers which could help you.