My boiler runs fine but shortly after starting I get a noise like short bursts of leaking air which continues after the boiler stops for a little while. No water anywhere so I dont think it is a water leak. The only thing that happened recently is that I had a new fan fitted but the noise doesnt seem to be coming from that but from behind the heat exchanger Any ideas?

Alan Brown, November 2007

Sounds like an air trap in the heat exchanger possibly caused by some debris. Isolate the boilers water inlet and outlet then drain the exchanger, re-fill and see if this cures it. http://www.betgizmo.com

Andy, December 2008