im not gonna have someone else tell me that all the pumps i changed didnt need changing and that it must have been a coincidence that the system suddenly started working once i filled the boiler back up.

the system doesnt just need to be blocked up with sludge to wear a pump out

hard water will have the same effect and combi's will wear out pumps much quicker than if they were fitted on a Y or S plan system due to the fact they are stop start all the time