How do i fix a noisy baxi Bermuda back boiler?

Just recently went away on holiday turned water off, came back put water back on, and noticed no cold water coming from tank in loft. Fixed this by backfeeding hot water through cold. since this time, my boiler has been so noisy, it sounds like it is going to blow. I have turned it off, also another problem is that the pump will not switch off on the programmer please advise.