pilot light goes out

[frustrated alpha]

i have a 6yr old alpha 280p
i changed gas valve,overheat thermo,exchanger,cleaned all rads and pipes,but pilot light keep on going out with a metallic bang............any help please

 

[namsag]

What about the actual sensors which in effect are the boiler stats if boiler gets too hot it will trip pilot,also pilot has to be spotless so it doesn`t pull away from t/couple when fan comes on full

 

[frustrated alpha]

i think there are two sensors there one near exchanger the ather mounted on pipe going up to main burner,is that what u mean?