Overheating Eurocal oil fired combi boiler

[neepielantern]

I have a eurocal oil fired combi boiler, it fires up, heats the radiators and hot water, but doesn't cut out when everything is up to temperature, it keeps firing until the high temp stat locks out the boiler, you can hear the water boiling inside. I have replaced the thermal store stat and control stat, but it is still the same.
Anyone have any idea ?

 

[kimbo]

Only ever seen one of these boilers and I walked away.

 

[lance]

Well , there is only the hi limit stat left. I agree one of those you changed usually does it.