i had the same problem with my boiler and i called a plumber he stiched me big time i have learnt alot since then all you need to do is remove the water pump and de-scale it you can buy the acid they use from most diy stores for under 10 pounds takes about 2hrs then get a preasure water pipe and run the water if the water is smooth you are ok. dont get worried about removing it just take pictures of what you remove and write down the steps you take it out... good luck ps you can also go to a boiler shop and ask them
luke four-lookfourathotmaildotcom
September 2006