Glowworm boiler - Pilot Light goes out

[jaguk]

The pilot light on my 15 year old boiler keeps going out. When you switch on the CH it will run OK for about 30mins than there is a large clunk and the system stops and the pilot light goes out.

System runs OK when heating the water in the CW tank.

British gas have attended 6 times now and have replaced the pump and a number of other items but have not solved the problem. They are now suggesting a system flush which is going to cost an arm and a leg (possibly both legs!).

I have drained the system and refilled but still have the problem.

HELP

 

[kevplumb]

System runs OK when heating the water in the CW tank.

i hope its not

boiler make /model etc

British gas have attended 6 times now and have replaced the pump and a number of other items but have not solved the problem. They are now suggesting a system flush which is going to cost an arm and a leg (possibly both legs!).

what bit's

 

[jaguk]

You noticed my deliberate mistake.

The boiler is a glowworm Fuelsaver MKII.

British Gas have changed the thermostat and the pump and have performed a full service. They also changed a wire that they stated was covered in soot but unfortunately I didn't ask what it was.

One more bit of info, when I was trying to sort the problem I did notice that one of the rads is failing to even get warm. Have bled it, no bubbles but the water is cold.