Could be airlocked, if so you'll also hear banging noises and shoud switch boiler off immediately and check the water level in the header tank (a small tank holds aboput7 gallons of cold water isn't below the "feed pipe" coming out of the tank to the boiler. If OK try bleeding the radiators, then you start working through faulty pumps, solenoids, boiler thermostats and sensors. Always best to start with the easy stuff first
The Gasman, November 2015
