My boiler makes a buzzing noise when switching on my central heating. Hot water works fine. No central heating. This morning the pressure was too low so I filled it to 0.8 then as the boiler was trying to start up the central heating, the pressure went up to 1.5. It has now dropped to 1.1. Just hope it's nothing too expensive. Any help would be much appreciated.

Matt, February 2012

First to look is pressure relief valve loosing water any sign of water out side ,if it's change it,next look is expansion vessel ,any water leak in property heating pipe

ltd, February 2012