noisy johson and starley modairflow boiler?

My Dad is 90 years old and has the above boiler.on Friday he complained it was making a terrible sqealing noise and had turned it off. i got a neighbour to look at it and he pushed a piece of cardboard in which stopped it sqealing. However today it was making a dreadful rumbling noise and he's turned it off again as he was frightened. It is minus 8degrees here and we need some advice. Please can anybody help?