Potterton Suprima boiler problems goes off too quick

Boiler comes on with a bit of a yellow flame .. good time to do a co test and service but.. sounds like overheating and kettling .. a good time to check what the pump is doing? because 90% of the time its the faulty pump not dissipating the heat from the boiler cause the boiler to overheat & kettle and then boiler goes off until the flow temperature falls back to boiler primary set temperature on the boiler thermostat or the high temperature may cause the boiler overheat stat to activate and to lockout.
The circulation pump of this system was replaced and the boiler was serviced and put back to work.
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