Jaguar 28k combi boiler?

I have exactly the same boiler and have had the same problem. It appears as though it is the expansion vessel with my system.

10clamp
January 2010

with the system a ZERO pressure,test what pressure you have in the expansion vessel ,
NOTE if water comes out when you depress the valve core
the pressure vessel internal diaphragm has failed the pressure vessel will need to be replaced.
if no water comes out re inflate pressure vessel to about 1 bar MAX using a car pump ,then refill system with water via the filler loop

wirecutterman
December 2009