Hi new here and would appreciate some advice. My central heating failed recently. After reading a few forums I checked the pump( Myson) at the bleeding point the spring loaded screw wasn't turning so purchased a new Grunfos pump and fitted. The system now fires up pump is running but after a minute or so boiler overheats and cuts off. Again after reading another post suggesting pump flow direction should be pointing down because pump is connected to upper outlet of boiler so done this still same problem. My concern just now is when I removed the head to check that the impeller was turning it looks as though it is running in reverse e.g not a scooping action. Is this correct. I have wired it as instructed L to L ,N to N and E to E. When it overheats the pipes at the pump are not hot yet but with conduction eventually heat reaches pipe going into pump at top first. Any suggestions please.