It is worth giving system a chemical clean. For £15 you can buy a litre of Sentinel X400 and let it circulate for 4 weeks before you drain it out, rinse, and add inhibitor. It is nopt time critical so you can do it at your leisure, but after 4 weeks it starts to lose its power.
If your system is an old open vented one, it will usually have a lot of black sediment in it, and this is one of the things that clogs pumps and wears them out.
Thanks, I guess now is the time to do it before winter comes around again!