I have a 20 year old Worcester Heatslave 20/25. The heating and hot water are switched off. The pressure gauge (fitted a couple of months ago) is showing 3 bar and dumping water through the overflow outside. The filling loop has been replaced and I can confirm there is no water coming through it. There is a sound of flowing water into the bolier. If the filling loop is isolated what is causing the pressure gauge to read 3 bar? Even if I purge it down to 1 bar, it soon climbs back up.

Puzzled, March 2014

Changed expansion tank, as this was spraying out water. Same over pressurization occurred. Changed Heat Exchanger, as suggested above, and fixed problem. Temperature at taps and radiators seems a lot hotter than with the old Heat Exchanger

Puzzled., March 2014

Try turning the cold water feed off to the boiler there should be an isolator on the boiler,it sounds like the cold water is leaking into central heating circuit through the heat exchanger

toptrish, March 2014