the f&f tank lvl is really not a problem unless it is empty and the cold feed pipe isnt a worry unless it is blocked although microbore is a bit on the small side as a general rule its 15 mm sometimes 22mm you would know if it was blocked as the rads wouldnt fill upstairs when u try to release the air
u did make sure the trv,s are open? i just cant understand why an engineer cant solve the problem on sight, with more information i could probably solve it pretty quick, is the boiler sighted downstairs? r u on a H plan and if so is it high enough above the pump as to close to the pump will cause a problem with airlock is the bypass valve open to wide as this will cause some rads not to work check these out get back to me
sean, November 2009