DIY Doctor UK DIY Forums

my problem is as follows: the boiler switches on and off quite rapidly and whilst the rads do warm up but not hot, the water gets mega hot.
Finally the boiler shuts down and i lose all heat.
I then run off the very hot water into the bath and an airlock seems to happen as the water splutters out ( discoloured ) and then the boiler will restart. I have had a new pump installed by a plumber who now thinks the 3 port valve may need renewing, any ideas? davy

Hi Davy,

Need more info on system as much info as you can give.

hi steve, the boiler is a Myson Economist WF30/40 BF, about 20 years old. There are 5 rads plus a towel rad in bathroom.
Water tank and new Grunfoss pump, Honeywell 3 port valve are in loft. thats about it.
By the way I have water switched OFF on the Centaur Plus C27 controller, but still get mega hot water. Davy

Hi,

Could you lock the slider on 3 port valve to the manual position and post back?