How can I fix the overflow on a worcester 28i junior?

when did you last check the pressure in the expansion vessel ? you do this test with no water pressure in the system inflate the vessel with a car foot pump to 1 bar max pressure, then repressurise system on the water side using the filler loop to 1 to 1.5 bar cold disconnect one end of the filler loop.

wirecutterman
October 2010