Originally Posted by the sludge
the boiler runs for like 2 or 3 minutes then goes off. there are no thermo valves except for the one in the extension that was added.
stick a new pump in it mate - that boiler should run for about 20mins at least before it has to modulate down to low flame.
is it noisy just before it shuts down?
sounds like it has circulation problems, thats why it shuts down early because the heat is staying in the boiler.