I have a f23e sanier duval boiler.The pressure gauge rises to 4 when we put the heating on and then water starts leaking the safety valve. After switching off the heating the water pressure goes down to zero.
I have changed the sensor but no joy.Is there any blockage in the system?

Baldev, May 2010

This is a common problem on this boiler it is most likely to be a blockage in the braided pipe that joins the hydraulic block to the expansion vessel drain the boiler, remove and clean the inside of the pipe, check expansion vessel recharge as necessary, refill the system. Simples!

copperpipeman, May 2010